diff options
Diffstat (limited to 'old/56113-0.txt')
| -rw-r--r-- | old/56113-0.txt | 6500 |
1 files changed, 0 insertions, 6500 deletions
diff --git a/old/56113-0.txt b/old/56113-0.txt deleted file mode 100644 index 0131844..0000000 --- a/old/56113-0.txt +++ /dev/null @@ -1,6500 +0,0 @@ -The Project Gutenberg EBook of Irrigation Works, by E. S. Bellasis - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - - - -Title: Irrigation Works - The Principles on which their Design and Working should be Based... - -Author: E. S. Bellasis - -Release Date: December 3, 2017 [EBook #56113] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK IRRIGATION WORKS *** - - - - -Produced by Chris Curnow, Harry Lame -and the Online Distributed Proofreading Team at -http://www.pgdp.net (This file was produced from images -generously made available by The Internet Archive) - - - - - - - Transcriber’s Notes: - - Text between _underscores_ and =equal signs= represent text printed in - italics and bold face respectively; ^{text} represents superscript - text; [·1] represents ·1 with a bar above. Small capitals have been - transcribed as ALL CAPITALS. - - More Transcriber’s Notes may be found at the end of this text. - - - - -IRRIGATION WORKS - - - _By the Same Author_ - - RIVER AND CANAL ENGINEERING. The Characteristics of Open Flowing - Streams, and the principles and methods to be followed in dealing with - them. 72 illustrations, x + 220 pp., 8vo (1913). - - =8/6= net. - - PUNJAB RIVERS AND WORKS. Second Edition. 47 illustrations, viii + 64 - pp., folio (1912). - - =8/-= net. - - HYDRAULICS WITH WORKING TABLES. Second Edition. 160 illustrations, xii - + 311 pp., 8vo (1911). - - =12/-= net. - - THE SUCTION CAUSED BY SHIPS. Explained in Popular Language. 2 plates, - 26 pp., 8vo, sewed (1912). - - =1/-= net. - - E. & F. N. SPON, LTD., LONDON - - -[Illustration: BRIDGE ON AN INDIAN CANAL. - -_Frontispiece._] - - - - - IRRIGATION WORKS - - THE PRINCIPLES ON WHICH THEIR DESIGN - AND WORKING SHOULD BE BASED, WITH - SPECIAL DETAILS RELATING TO - INDIAN CANALS - AND SOME PROPOSED IMPROVEMENTS - - BY - - E. S. BELLASIS, M.INST.C.E. - - RECENTLY SUPERINTENDING ENGINEER IN THE IRRIGATION BRANCH OF - THE PUBLIC WORKS DEPARTMENT OF INDIA - - 37 Illustrations - - [Illustration] - - London - E. & F. N. SPON, LTD., 57 HAYMARKET, S.W. - - New York - SPON & CHAMBERLAIN, 123 LIBERTY STREET - - 1913 - - - - -CONTENTS - - - PAGE - PREFACE vii - - - CHAPTER I - INTRODUCTION - - ARTICLE - - 1. Preliminary Remarks 1 - 2. General Principles of Canal Design 2 - 3. Information concerning Canals 11 - 4. Losses of Water 16 - 5. Duty of Water 21 - 6. Sketch of a Project 26 - - - CHAPTER II - THE DESIGNING OF A CANAL - - 1. Headworks 30 - 2. The Contour Map 36 - 3. Alignments and Discharges 37 - 4. Remarks on Distributaries 45 - 5. Design of Canal and Branches 47 - 6. Banks and Roads 53 - 7. Trial Lines 58 - 8. Final Line and Estimate 59 - 9. Design of a Distributary 60 - 10. Best System of Distributaries 71 - 11. Outlets 76 - 12. Masonry Works 80 - 13. Pitching 90 - 14. Miscellaneous Items 93 - - - CHAPTER III - THE WORKING OF A CANAL - - 1. Preliminary Remarks 96 - 2. Gauges and Regulators 103 - 3. Gauge Readings and Discharges 106 - 4. Registers of Irrigation and Outlets 113 - 5. Distribution of Supply 118 - 6. Extensions and Remodellings 127 - 7. Remodelling of Outlets 131 - 8. Miscellaneous Items 137 - - - CHAPTER IV - THE PUNJAB TRIPLE CANAL PROJECT - - 1. General Description 144 - 2. Areas and Discharges 147 - 3. Remarks 156 - - - CHAPTER V - PROPOSED IMPROVEMENTS IN IRRIGATION CANALS - - 1. Preliminary Remarks 158 - 2. Reduction of Losses in the Channels 159 - 3. Modules 162 - - - APPENDICES - - A. Divide Wall on Lower Chenab Canal 169 - B. Specification for Maintenance of Channels 171 - C. Specification for Maintenance of Masonry Works 174 - D. Watching and Protecting Banks and Embankments 175 - E. Specification for Bushing 178 - F. Escapes 180 - G. Gauges 183 - H. Gibb’s Module 186 - K. Kennedy’s Gauge Outlet 193 - - INDEX 196 - - - - -PREFACE - - -When _River and Canal Engineering_ was written it was decided to omit -Irrigation works and to deal with them separately because the subject -interests chiefly specialists. - -The present book deals with the principles which govern the design and -management of Irrigation works, and it discusses the Canals of Northern -India--the largest and best in the world--in detail. - -Some years ago a number of rules for designing distributaries were -framed, at the request of the Punjab Government, by the late Colonel S. -L. Jacob, C.I.E., R.E., and comments on these rules were obtained from -many experienced engineers and recorded. The author has had the -advantage of reading all these opinions. Generally the weight of opinion -on any point agrees with what most experienced engineers would suggest, -and direct conflicts of opinion scarcely occur. Important papers have -been printed by the Punjab Irrigation Branch on Losses of Water and the -Design of Distributaries, on the great Triple Canal Project, on Gibb’s -Module, on Kennedy’s Gauge Outlet, and on the Lining of Watercourses. -These papers are not always accessible to engineers, and the chief -points of interest in them are not, in most cases, discernible at a -glance. Such points have been extracted and are given in this book. - - E. S. B. - - CHELTENHAM, _May_ 20_th_, 1913. - - - - -IRRIGATION WORKS. - - - - -CHAPTER I. - -INTRODUCTION - - -1. =Preliminary Remarks.=--The largest irrigation canals are fed from -perennial rivers. When the canal flows throughout the year it is called -a “Perennial Canal.” Chief among these are the canals of India and -particularly those of Northern India, some of which have bed widths -ranging up to 300 feet, depths of water up to 11 feet and discharges up -to 10,000 c. ft. per second. Other large canals as for instance many of -those in Scinde, Egypt and the Punjab, though fed from perennial rivers, -flow only when the rivers are high. These are called “Inundation -Canals.” Many canals, generally of moderate or small size, in other -countries and notably in the Western States of America, in Italy, Spain, -France and South Africa, are fed from rivers and great numbers of small -canals from reservoirs in which streams or rain-water have been -impounded. Sometimes water for irrigation is pumped from wells and -conveyed in small canals. In Australia a good deal of irrigation is -effected from artesian wells. Irrigation works on a considerable scale -are being undertaken in Mexico and the Argentine. In this book, -irrigation works of various countries are referred to and to some extent -described, but the perennial canal of Northern India, with its -distributaries, is the type taken as a basis for the description of the -principles and methods which should be adopted in the design, working -and improvement of irrigation channels and it is to be understood that -such a canal is being referred to where the context does not indicate -the contrary. Any reader who is concerned with irrigation in some other -part of the world will be able to judge for himself how far these -principles and methods require modification. The branches and -distributaries--all of which are dealt with--of a large perennial canal -cover all possible sizes. - -CHAPTER II. of this book deals with the design of canals and CHAPTER -III. with the working of canals but as the two subjects are to some -extent interdependent, they will both be dealt with in a preliminary -manner in the remaining articles of the present Chapter. CHAPTER IV. -describes the Punjab Triple Canal Project.[1] CHAPTER V. deals with -certain proposed improvements in the working of canals. - - [1] The latest example of canal design. - - -2. =General Principles of Canal Design.=--The head of a canal has to be -so high up the river that, when the canal is suitably graded, the water -level will come out high enough to irrigate the tract of land concerned. -If a river has a general slope of a foot per mile and if the adjoining -country has the same slope and is a foot higher than the water level of -the river, and if a canal is made at a very acute angle with the river, -with a slope of half a foot per mile, the water level about two miles -from the canal head will be level with the ground. - -The headworks of the canal consist of a weir--which may be provided with -sluices--across the river, and a head “regulator,” provided with gates, -for the canal. There are however many canals, those for instance of the -inundation canal class, which have no works in the river and these may -go dry when the river is low. They usually have a regulator to prevent -too much water from going down the canal during floods. If a canal is -fed from a reservoir the headworks consist simply of a sluice or -sluices. - -A canal must be so designed as to bring the water to within reasonable -distance of every part of the area to be irrigated. Unless the area is -small or narrow the canal must have “branches” and “distributaries.” A -general sketch of a large canal is given in Fig. 1. On a large canal, -irrigation is not usually done directly from the canal and branches. It -is all done from the distributaries. - -[Illustration: FIG. 1.] - -From each distributary “watercourses” take off at intervals and convey -the water to the fields. A small canal, say one whose length is not more -than 15 miles or whose discharge is not more than 100 c. feet per -second, may be regarded as a distributary and the word distributary will -be used with this extended meaning. - -It is not always the case that the whole tract covered by a system of -canal channels is irrigated. In the case of a canal fed from a river, -the land near the river is often high or broken and the main canal runs -for some distance before it reaches the tract to be irrigated. Again, -within this tract there are usually portions of land too high to be -irrigated. Those portions of the tract which can be irrigated are called -the “commanded area.” - -The channels of a large irrigation system should run on high ground. In -the case of a distributary, this is necessary in order that the -water-courses may run downhill, and since the water in the canal and -branches has to flow into the distributaries, the canal and branches -must also be in high ground. Another reason for adopting high ground is -that all the channels should, as far as possible, keep away from the -natural drainage lines of the country and not obstruct them. Also a -channel in high ground is cheapest and safest. When a channel is in low -ground it must have high banks which are expensive to make and liable to -breach. Every tract of country possesses more or less defined ridges and -valleys. When the ridges are well defined, the irrigation channels, -especially the distributaries, follow them approximately, deviating -slightly on one side or the other from the very top of the ridge in -order to secure a more direct course. If any part of a ridge is so high -as to necessitate deep digging the channel does not necessarily go -through it. It may skirt it and return to the crest of the ridge further -on, especially if this arrangement shortens the channel or at least does -not lengthen it much. A channel also goes off the ridge sometimes when -adherence to it would give a crooked line. Of course all the -channels--canals, branches and distributaries--have to flow more or less -in the direction of the general slope of the tract being dealt with. - -[Illustration: FIG. 2.] - -The alignments of the channels do not, however, depend exclusively on -the physical features of the country. Centrality in the alignment is -desirable. It will be shown (CHAP. II. Art. 10) that a distributary -works most economically when it runs down the centre of the tract which -it has to irrigate. It is better to have short watercourses running off -from both sides of a distributary than long watercourses from only one -side. The same is true of a branch; it should run down the centre of its -tract of country. Again the angles at which the channels branch off have -to be considered. If branches were taken off very high up the canal and -ran parallel to and not far from it, there would be an excessive length -of channel. But neither should the branches be so arranged as to form a -series of right angles. In the case shown in Fig. 2 the size of the -main or central canal would of course be reduced at the point A. By -altering the branches to the positions shown in dotted lines their -length is not appreciably increased while the length A B is made of the -reduced instead of the full size. Moreover the course B C is more direct -than BAC and this may be of the greatest importance as regards gaining -the necessary command. When a channel bifurcates, the total wet border -always increases and there is then a greater loss from absorption. The -water is always kept in bulk as long as possible. If the alignment of a -branch is somewhat crooked it does not follow that straightening -it--supposing the features of the country admit of this--will be -desirable. It may increase the length of distributaries taken off near -the bends. It will be shown (CHAP. II. Art. 10) that a distributary -ought, when matters can be so arranged, to irrigate the country for two -miles on either side of it, and watercourses should be two or three -miles long. A distributary need not therefore extend right up to the -boundary of the commanded area but stop two or three miles from it. -Generally it is not desirable to prolong a distributary and make it -“tail” into another channel (CHAP. II. Art. 3). A distributary, like a -canal, may give off branches. - -None of the rules mentioned in the preceding paragraph are intended to -be other than general guides, to be followed as far as the physical -features of the country permit, or to assist in deciding between -alternative schemes. It may for instance be a question whether to -construct one distributary or two, between two nearly parallel branches. -The two-mile rule may enable the matter to be decided or it may -influence the decision arrived at as to the exact alignments of the -branches. The flatter the country and the less marked the ridges the -more the alignment can be based on the above rules. Sometimes, as in the -low land adjoining a river, the ridges are ill defined or non-existent -and the alignment is based entirely on the above rules. The rule as to -following high ground need not be adhered to at the tail of any -distributary if all the land to be irrigated at the tail is low and if -there is a deep drainage line or other feature of the country such as to -preclude the possibility of an extension of the distributary. Possible -extensions should always be considered. In hilly districts an irrigation -canal may have to run in sidelong ground along the side of a valley. - -In flat valleys, owing to the land nearest the river having received -successive deposits of silt in floods, the ground generally slopes away -from the river and a canal can irrigate the low land even if taken off -at right angles to the river. But to irrigate the high land near the -river and the land where it rises again towards the hills or watershed, -a canal taking off higher up the river is necessary. Of course much -depends on whether the canal is to irrigate when the river is low or -only when it is high, and whether or not there is to be a weir in the -river. In Upper Egypt, it is common for a high level canal taking off -far upstream, to divide into two branches, one for the land near the -river and one for the land towards the watershed, and for both branches -to be crossed--by means of syphons--by a low-level canal which irrigates -the low ground. Similar arrangements sometimes occur on Indian -inundation canals. - -Regulators are usually provided at all off-takes of branches. In the -case of a channel taking off from another channel many times its own -size there is generally only the head regulator of the smaller channel -but in other cases there is a regulator in each channel below the -bifurcation. Thus, when the number of bifurcating channels is two it is -called a double regulator. Regulators, with the “falls”--introduced to -flatten the gradients when the slope of the country is too steep--and -drainage crossings and the bridges, provided at the principal roads, -constitute the chief masonry works on a canal. At a fall, mills are -often constructed or the fall may be used for electric power. - -Regarding curves and bends in channels, it is explained in _River and -Canal Engineering_ that, as regards increased resistance to flow and -consequent tendency to silt deposit, curves of fair radius have very -little effect, that a curve of a given angle may perhaps have the same -effect whether the radius is great or small but that if the radius is -large a succession of curves cannot be got into a short length, that a -succession of sharp curves in a short length may have great effect, -amounting to an increase of N in Kutter’s co-efficient, that a single -sharp curve has not much effect, that the chief objection to such a -curve is the tendency to erosion of the bank, that at a place where the -channel has, in any case, to be protected, as for instance just below a -weir or fall, there is no objection to the introduction of a sharp bend -and that such bends, in fact right-angled elbows, exist without any evil -effects at many regulators when the whole supply is being turned into a -branch. It is remarkable that on perennial canals no advantage is ever -taken of the last mentioned fact. Cases undoubtedly occur, though -somewhat infrequently, in which the most suitable and cheapest -arrangement would be to give a canal an abrupt bend at a fall. In order -to reduce eddying, the bend need not be an absolute elbow but can be -made within the length of the pitching which would be curved instead of -straight. This is frequently done on inundation canals, without the -slightest drawback, even when there is no fall, the pitching at bridges -being utilised. A pitched bend can be made anywhere. - -When a river floods the country along its banks as in parts of Egypt and -of the Punjab, it is generally necessary to construct marginal -embankments before irrigation can be introduced. The canal may take off -at a point where flooding does not occur or it may pass through the -embankment.[2] If it passes through at a point where flooding occurs, a -masonry regulator is constructed to prevent the floods from enlarging -the gap and breaking into the country. - - [2] For detailed accounts of such embankments and canals see _Punjab - Rivers and Works_ (Spon) 1912. - -A large canal is provided, so far as is practicable, with “escapes” by -means of which surplus water may be let out. Surplus water occurs -chiefly after rain. At such times the demand for water may suddenly be -reduced and if there were no escapes there would probably be serious -breaches of the banks before there was time for the reduction of water, -effected at the head of the canal, to take effect lower down. There is -usually an escape at some point in the main line, preferably at a point -where it divides into branches, and this escape runs back to the river. -There may also be escapes near the tails of the longest branches. These -escapes may discharge into drainages or into reservoirs formed by -running a low embankment round a large area of waste land. - -The drainage of the whole tract irrigated by a canal must be carefully -seen to. The subsoil water level of a tract of country is nearly always -raised by an irrigation canal. The rise near to a canal or distributary -is due to percolation from the channel and is inevitable.[3] The rise at -places further away, if it occurs, is due to over-watering or to neglect -of drainage. Immense damage has been done by “water-logging” of the soil -when irrigation water has been supplied to a tract of flat country and -the clearance and improvement of the natural drainages has not been -attended to. Any drainages crossed by the banks of the irrigation -channels should be provided with syphons or aqueducts or else the -drainage diverted into another channel. Very frequently the main line of -a canal--whether great or small--in the upper reaches near the hills, -has to cross heavy drainage channels or torrents and large and expensive -works are required for this. - - [3] But see Chap. V. as to reduction of percolation. - -Near the head of a canal and of every branch and distributary, there is -an ordinary gauge which shows the depth of water and is read daily. The -gauge near the head of a main canal is generally self-registering. - -The principles sketched out in this article are those generally followed -in the designs of modern canals. They have by no means been followed in -all cases. In some of the older Indian canals both the canal and the -distributaries ran in low ground. Water-courses took off direct from the -canals, and the irrigation did not generally extend far from the canal. -In fact long distributaries were impracticable because they would have -run into high ground. The banks of the channels obstructed drainages and -caused pestilential swamps. Most canals of this type have been -abolished since the advent of British rule and replaced by others -properly designed. Some badly designed canals however, mostly of the -inundation class, still exist but in very dry tracts where drainages are -of little consequence. - - -3. =Information Concerning Canals.=--Nearly all canal irrigation is done -by “flow,” the water running from the water-courses onto the fields, but -a small proportion is done by “lift.” This is done in the case of high -pieces of land, the lifting being usually done by pumps or, in the east, -by bullocks or by manual labour. - -Irrigation generally consists in giving the land a succession of -waterings, one previous to ploughing and others after the crop is sown, -each watering being of quite moderate depth. On inundation canals in -India the waterings for the summer crop are thus effected but for the -winter crop the land is deeply soaked during the flood season and is -afterwards ploughed and sown. In Upper Egypt this system is emphasised, -the water flowing into vast basins, formed by dykes, where it stands for -some time and, after depositing its silt, is drained off. - -Until recent times the whole of the irrigation of Egypt was basin -irrigation. In Lower Egypt the construction of the Nile barrage led to -the introduction of canals which take off at a proper level and their -working is not restricted to the period when the river is in flood. In -Upper Egypt most of the irrigation is still basin irrigation but the -canals taking off above the Assiut barrage form a notable exception. By -means of the Assouan dam which crosses the Nile, the water during the -latter part of the flood season and after the floods are over, i.e. from -November to March, is ponded up and a vast reservoir formed and the -impounded water is let down the river in May and June. - -In some of the older irrigation canals of India the velocity was too -high and the channels have since had to be remodelled and the crests of -weirs raised or new weirs built. The more recent canals are free from -grave defects of this kind but every canal undergoes changes of some -kind and finality has never yet been quite attained. - -On some Indian irrigation canals made about 30 years ago, great sums of -money were wasted in making the canals navigable. There is nothing like -enough navigation to pay for the extra cost. The idea has now been quite -given up except as regards timber rafting from upstream. This requires -no curtailment of the velocity in the channels. The requirements of the -irrigation and navigation were always in conflict. The mere fact that -branches have to be worked in turns is enough to prevent navigation -succeeding. - -In India the water used for irrigation is paid for, not according to the -volume used but according to the area irrigated. The volume used in any -particular watercourse is not known. The areas sown are measured. -Certain kinds of crops use up more water than others and the charges are -fixed accordingly. - -In the canals which have their headworks among the mountains of Western -America there are frequent tunnels and syphons and the canals often run -in steep sidelong ground. There are great lengths of tunnel and syphon -in the Marseilles and Verdun Canals and there are long tunnels in the -Periyar Canal in Madras and in the Upper Swat Canal in the North West -Frontier Province of India. - -The Tieton Canal, Washington, U.S.A., traverses steep sidelong ground -which would be liable to slip if a large cutting were made. The -cross-section of the channel is a circle, 8-ft. 3¹⁄₂-ins. in diameter, -with the upper part removed, so that the depth is 6 feet. It is made of -reinforced concrete 4 inches thick and the sides are tied together by -iron bars which run across the channel above the water. In the Santa Ana -Canal the channel consists for 2¹⁄₂ miles of a flume made of wooden -“staves.” - -A canal constructed in Wyoming, U.S.A., after taking off from a river, -passes through a tunnel into another valley and is turned into another -stream which thus becomes the canal. This is said to save loss of water -by percolation. The stream is winding while a canal could have been made -straighter. There may, owing to the ground near the stream being -saturated, have been less loss of water at first than there would have -been in the artificial channel but, owing to the smaller wetted area, -there would probably have been an eventual saving in adopting the -latter. The real advantage of adopting the natural stream was probably a -saving in the cost of construction. (_Min. Proc. Inst. C.E._ Vol. -CLXII.) - -Irrigation from canals which are supplied from reservoirs differs in no -respect from that from other canals. The principles on which reservoir -capacities should be calculated and earthen and masonry dams constructed -are given in _River and Canal Engineering_. Sometimes, as for instance -when a reservoir becomes seriously reduced in size owing to silt -deposit, the water is run off after the bed of the reservoir has been -soaked, and crops are grown on the soaked soil. - -The distribution of the water of a canal as between the main channel and -the branches, is effected by means of the regulators at the -bifurcations. When the supply is ample and the demand great, the -channels may all be running nearly full. When the demand exceeds the -supply, the water may be reduced proportionately in each branch but this -may result in the water of a branch being too low to give proper -supplies to the distributaries or some of them, and in the water of a -distributary not commanding the higher ground. Moreover it violates the -principle of keeping the water in bulk as far as possible. It is more -usual to give each branch full supply, or a certain large fraction of -the full supply, in turn, and similarly with the distributaries. - -The method of distribution from a distributary to the watercourses -varies. In many modern canals there is, at each watercourse head, a -sluice which is adjusted at frequent intervals according to the supply -and the demand. One method, which is excellent because it fulfils in the -highest degree the principle of keeping the water in bulk, is to have -very large watercourses and, by means of regulators which are built at -frequent intervals, to turn the whole of the water of the distributary -into a few watercourses at a time, beginning with those nearest the head -of the distributary and working downstream. But a system which seems -eminently suitable may be impracticable because of local circumstances. -In India, any such arrangement would need an army of officials and would -lead to unbounded corruption. - -In India the water from a distributary enters the watercourses through -“outlets” which are small masonry tubes passing through the banks of the -distributary. There is no easy way of closing these outlets or at least -of keeping them closed if the cultivators choose to open them, but it is -easy to close a whole distributary and so regulate the supply. This is -the chief reason why watercourses in India do not usually take off -direct from the canals. - -The presence of silt in the water of a river from which a canal is drawn -is often spoken of as being a great evil. If it is an evil at all it is -a very mixed evil. The deposits of silt in the channels have been -enormously reduced by the application of scientific principles of -design. The clayey silt which remains in the water and reaches the -fields, brings to them greatly increased fertility. - -In India the fertility of the soil is often reduced or destroyed by the -formation on the surface of the ground of an efflorescence called “reh.” -It consists of various salts or compounds of sodium and occurs chiefly -where there is an impervious layer of subsoil. The salts exist as an -ingredient of the upper soil. This becomes saturated with rain or canal -water and as the water evaporates the salts are left on the surface. -Remedies are drainage, or flooding the soil and running the water off, -or deep tilling, or chemical treatment with lime or gypsum. (_Indian -Engineering, 8th Jan., 1910_). - -The inundation canals of the Punjab have been described in _Punjab -Rivers and Works_. All descriptions and remarks in the present book -regarding Indian canals must be assumed to refer to perennial canals -unless the contrary is stated or implied. - - -4. =Losses of Water.=--When water flows or stands in an earthen channel -or tank, or is spread over a field, losses occur from evaporation, -percolation and absorption. Of these, absorption is by far the most -important and, unless the contrary is stated or implied, it will be -taken to include the others. The losses by evaporation are very small. -The loss by evaporation from the surface of the water, even in the hot -season in India when a hot wind often blows, does not exceed half an -inch in 24 hours and on the average in India is only about a tenth of an -inch in 24 hours. - -[Illustration: FIG. 3.] - -Percolation and absorption are described as follows by Beresford in -_Punjab Irrigation Paper_, No. 10, “The Irrigation Duty of Water.” -Percolation consists in flow through the interstices of boulders, -shingle, gravel or coarse sand. The flow is similar to that in pipes. -The water percolating into the soil from a channel, extends downwards -and spreads outwards as it descends. None of it goes upwards. In fine -sand and ordinary soil the interstices act like capillary tubes. The -water is absorbed as by a sponge and it remains in the soil by virtue of -capillarity. Owing to the combined action of capillarity and gravity the -water spreads in the manner shown by the dotted lines in Fig. 3. The -amount of absorption from a channel will be greater the greater the area -of the wetted surface. In a high embankment with narrow banks, the -absorption ceases when the water reaches the outer slopes, except in so -far as it is evaporated from the slopes. Moreover high embankments are -generally in clayey soil. If banks of sand are constructed on a layer of -clay (Fig. 4.) and well rammed, the absorption ceases as soon as the -banks are saturated and the channel then holds water as well as any -other except for evaporation from the outer slopes, but if the bed and -subsoil are also of sand the absorption of the water will be far -greater. Absorption ceases when the water extends nearly down to the -level of the subsoil water, i.e., to a point where the effect of -absorption from above plus gravitation is equal to the effect of -absorption from below minus gravitation. If a bottle is filled with -water and a small sponge jammed into the neck and the bottle turned -upside down, the sponge becomes saturated but no water will be given -out. But if a dry sponge is placed in contact with the wet one it will -absorb moisture until saturated. - -[Illustration: FIG. 4.] - -It is known that the loss of water is greatly influenced by the nature -of the soil. When water is turned into a dry channel or onto a field, -the loss is at first great. It decreases hourly and daily and eventually -becomes nearly constant, tending to reach a fixed amount when the water -extends down to nearly the level of the subsoil water. Observations made -by Kennedy on loamy fields near the Bari Doab Canal in India showed that -on a field previously dry the rate of absorption is given by the -equation - - _y_ = ·0891_x_^{·86.} - -Where _y_ is the depth of water absorbed in feet and _x_ is the time in -hours. The observations extended over eight days. Denoting by _c_ the -depth of water in feet absorbed in one hour, it was found that on a -field on which no rain had fallen for two months, _c_ was ·04 to ·05 but -on the second watering of the crop about a month later _c_ was ·02 to -·03 and about the same on a third watering. It was found that at the -first commencement the rate of absorption was much affected by the state -of the surface of the ground but that the effect was only temporary. The -losses were found to be as follows: - - +------+--------------+---------------+ - | DAY. |LOSS PER DAY. | LOSS PER HOUR.| - | | | (_c_) | - +------+--------------+---------------+ - | | Feet. | Feet. | - | 1st | 1·36 | ·057 | - | 2nd | 1·13 | ·047 | - | 3rd | 1·07 | ·046 | - | 4th | 1·02 | ·043 | - | 5th | ·96 | ·041 | - | 6th | ·90 | ·037 | - | 7th | ·80 | ·033 | - | 8th | ·77 | ·032 | - | | Total 8·01 | | - +------+--------------+---------------+ - -In the eight days the total loss was almost exactly eight feet. - -The losses by absorption in the various channels of certain canals has -been estimated to be as follows:-- - - ---------------+-------+----------+-------+-----------+--------------- - Channel. | Nature|Mean depth| Value | Loss per | Remarks. - | of | of water | of | Million | - | soil. | in | (_c_) |square feet| - | | Channel.| | of wetted | - | | | | surface. | - ---------------+-------+----------+-------+-----------+--------------- - | | Feet. | | c. ft. | - | | | | per sec. | - Main Line Upper|Shingle| 6 |·035 | 9·7 }| - Bari Doab Canal|and | | | }| - |Sandy | | | }| - |Soil | | | }| - | | | | }|Fairly reliable - Main Line |Sandy | 7 | | 9·0 }|estimates based - Sirhind Canal |Soil | | | }|on discharge - | | | | }|observations. - Branches Upper |Loam | |·0079 | 2·2 }| - Bari Doab Canal| | | | }| - | | | | }| - Branches |Sandy | | | 5·2 }| - Sirhind Canal |Soil | | | }| - | | | | | - Distributaries |Loam | |·012[4]|2·3 to 4·4}| - Upper Bari | | | | (average }| - Doab Canal | | | | 3·3) }| - | | | | }| - Distributaries |Sandy | | | 5 to 12 }| - Sirhind Canal |Soil | | | (average }| - | | | | 8·0) }|Somewhat rough - | | | | }|estimates. - Watercourses |Loam | |·015[4]| 3·3 to 20}| - Upper Bari | | | to | (average }| - Doab Canal | | |·045[5]| 9·4) }| - | | | | }| - Watercourses |Sandy | | | 7 to 60 }| - Sirhind Canal |Soil | | | (average }| - | | | | 22) }| - ---------------+-------+----------+-------+----------+---------------- - - [4] When the channel was in continuous flow. - - [5] Maximum value when flow was intermittent. - - -Some information as to losses of water is also given in CHAPTER IV. Art. -2. - -The relative losses of water in the channels of the Upper Bari Doab -Canal were as follows:-- - - Relative Loss. - In main line and branches 20 - In distributaries 6 - In watercourses 21 - Used in the fields 53 - --- - Total 100 - -The reasons for the great variation in the value of _c_ are not properly -known. The depth of water is not likely to have much influence on it. It -is well known that the fine silt carried by the water tends to render -the channels watertight when it deposits. The canals and branches -receive either no deposits or deposits consisting chiefly of sand. The -distributaries, especially in their lower reaches, receive deposits of -fine silt which is only occasionally cleared away. The watercourses -receive similar deposits but they are very frequently cleared out by the -cultivators. This is perhaps the reason why the rate of loss of water in -the watercourses is nearly three times as great as the rate of loss in -the distributaries of the same canal. On the Sirhind canal the -distributaries have more branches than on the Bari Doab canal and the -watercourses are smaller. This accounts for the different relative -losses in the two cases. The sandy nature of the soil on the Sirhind -canal accounts for the general higher value of _c_ on that canal. - -The following formula has been deduced as giving the loss by absorption -on a Punjab Canal. - - WL - P = 3·5 √d --------- - 1,000,000 - -Where P is the loss by absorption in c. ft. per second in a reach whose -length is L, width (at water level) W and depth d. According to the -formula the loss per million square feet is 10·5 c. ft. per second when -d is 4 ft. and 7 c. ft. per second when d is 2 feet, These figures do -not agree with those in the preceding table and it is clear that there -are not yet sufficient data from which to construct a formula. - -The first steps taken on the Bari Doab Canal, and subsequently on other -canals, to reduce the losses of water, consisted in the reduction in the -number of watercourses. This will be referred to again (CHAPTER II. Art. -9). Further steps will be considered in CHAPTER V. - - -5. =Duty of Water.=--The number of acres irrigated annually by a -constant discharge of 1 c. ft. of water per second is called the “duty” -of water. In India on perennial canals the duty may be as much as 250 or -even 300 acres. On inundation canals which flow for only five months in -the year and are situated in tracts of scanty rainfall and light or -sandy soil, the duty may be only 70 acres. The duties of most existing -canals whether in India or elsewhere, are known only approximately. The -duty is calculated on the average discharge entering the canal at its -head less the water which is passed out at escapes. It thus includes all -losses of water. The duty varies not only as between one canal and -another but on the same canal from year to year. It depends on the -character of the soil, a sandy soil requiring more water than a clayey -soil. It also depends on the rainfall. A moderate amount of rain causes -the canal water to go further, but heavy rain may enable some crops to -do without canal water or may permit of the concealment of canal -irrigation. The duty also depends on the kind of crops grown, on the -losses in the channels by absorption and on the quantity of water -available. A liberal supply of water leads to carelessness in the use, -but a very restricted supply is largely wasted owing to the shortness of -the “turns” or rotational periods of flow in the different channels. - -There is an obvious connection between the duty of water and the total -depth of the water, known in India as “delta,” given to the fields. -Calculations are much simplified, while still being accurate enough for -all practical purposes, by assuming that the number of seconds, (86,400) -in a day is twice the number of square feet, (43,560) in an acre. -Assuming this to be the case a discharge of 1 c. ft. per second for a -day gives 2 acre-feet, i.e., it will cover an acre of ground to a depth -of 2 feet in a day; and in six months it will cover 100 acres to depth -of 3·65 feet. In Northern India the year is divided into two halves in -each of which a crop is grown and the duty is calculated for each crop. -In this case, if the flow of a canal has been continuous, a duty of 100 -acres per cubic foot of its mean discharge per second, corresponds to a -total depth of 3·65 feet over the area irrigated. Generally the flow in -the half-year has not been continuous. In other countries, and in India -on canals other than the perennial canals, the periods of flow vary a -great deal. The duty cannot be calculated from delta or _vice versa_ -until the period of flow is stated. - -The daily gauge-readings and daily discharges corresponding to them, -having been booked, the discharges are added up. The total, divided by -the number of days on which the canal has been running, gives the -average daily discharge. Suppose that during the “kharif” or summer crop -which is considered to last from 1st April to 30th September or 183 -days, the canal was closed for 13 days and that the total of the daily -discharges on the remaining 170 days comes to 850,000 c. ft. per second. -The average daily discharge is 5,000 c. ft. per second. Suppose the -kharif area irrigated to be 500,000 acres, the kharif duty is 100 acres. -To find delta the total of the daily discharges has to be multiplied by -the number of seconds in a day and divided by the number of square feet -in an acre (these figures are, as already stated, very nearly in the -ratio of two to one) and divided again by the number of acres irrigated. -Thus, in the above case, delta is very nearly 850,000 × 2/500,000 or 3·4 -feet. For comparing the results of one canal or one year with another, -delta is the more convenient figure to take. As soon as the areas -irrigated by the canals are known for any crop, the Chief Engineer of -the province issues a statement of the value of delta for each perennial -canal and compares them with those for previous years. The value of -delta for the Punjab canals ranges from 3 to 4 feet for the kharif and -from 1·8 to 2·1 feet for the “rabi” or winter crop. Individual canals -vary greatly, the worst having nearly twice as high a figure as the -best. The differences are due to the causes already mentioned. - -Although the figures of duty take no account of the number of days a -canal was closed, they are the most convenient standard for judging -generally of the work likely to be done by a projected canal. It will -readily be seen that figures of duty are not exact and are only an -approximate guide. The delta figures are, on the perennial canals of the -Punjab, also worked out for each month of the crop, the volume of water -used from the beginning of the crop up to the end of the month being -divided by the area irrigated up to the end of the month. But when -irrigation is in full swing, some little delay occurs in booking the -fields. Moreover the same field is watered a number of times during the -crop and much depends on whether waterings have just been given or are -just about to be given. The figures are useful to some extent for -comparison. The figures for the rabi crop of 1908-09 were as follows, -the figure for March being the final figure for the crop. - - Up to end of Oct., Nov., Dec., Jan., Feb., March. - Progressive value of delta. 1·69 1·34 1·29 1·47 1·71 2·05. - -One great principle to be followed in order to obtain a high duty is to -restrict the supply of water. A cultivator whose watercourse is always -running full may waste great quantities of water, but if he knows that -it is only to run for a few days out of a fortnight he will use the -water carefully. It is not, of course, meant that the water kept back is -run into escapes and wasted. It goes to irrigate other lands. The -available supply of water should be spread over as large an area of land -as just, and only just, to suffice.[6] Other methods of improving the -duty are the reduction in the number of watercourses, the apportionment -of the sizes of outlets, watercourses and distributaries to the work -that they have to do, careful attention to the distribution of the water -and the prevention of wastage due to carelessness. - - [6] A system of lavish supply is in most cases likely to lead to harm - by water-logging of the soil or its exhaustion by over-cropping or to - raising of the spring level and injury to the public health. - -The following information concerning duties is taken from Buckley’s -Irrigation Pocket Book:-- - - +---------------------+-------------+-----------+ - | PLACE. | RABI DUTY. |KHARIF DUTY| - +---------------------+-------------+-----------+ - | | Acres | Acres | - | | | | - |Upper India |135 to 237[7]| 49 to 120 | - |(Punjab and | | | - |United Provinces) | | | - | | | | - |Lower Chenab Canal[8]|133 to 134 | 47 to 88 | - |(Punjab) | | | - | | | | - |Bengal | 56 to 130 | 57 to 113 | - | | | | - |Bombay | 85 to 118 | 58 to 159 | - +---------------------+-------------+-----------+ - - [7] Occasionally as low as 98 or even 62. - - [8] The most recent canal. - -The period of flow in each case would be six months or less. - -The average rabi duties on the Lower Chenab and Upper Bari Doab Canals, -in the Punjab, calculated on the discharges at the distributary heads, -for periods of 3 and 5 years respectively, ending March, 1904, were 208 -and 263 acres respectively, but in the latter case 11 per cent. of the -area received only “first waterings.” For the kharif the figures are 100 -and 98 respectively. - -In Italy the duty is 55 to 70 acres, in Spain from 45 to 205 acres, in -the Western States of America generally 60 to 150 acres. In South -California the duty is 150 to 300 acres, when, as is usual, surface -irrigation is employed, but 300 to 500 acres with subsoil irrigation, -the water being delivered in a pipe below ground level (CHAPTER V.) - -In basin irrigation in Egypt the duty is 20 to 25 acres, but the period -of flow is only 40 days. The basins are flooded to about 3 feet in -depth. - - -6. =Sketch of a Project.=--The tract of country to be dealt with in an -irrigation project may be limited either by the natural features of the -country, by its levels, by the quantity of water available or by -financial considerations. If the tract is small or narrow, and -particularly if it is not very flat, it may be obvious that there is -only one line on which the irrigation channel can conveniently be -constructed but in any considerable scheme a contour plan of the whole -tract is absolutely necessary. The surveys for such a plan are expensive -and take time and it is desirable, as far as possible, to settle -beforehand the area over which they are to extend. This may be done to -some extent by the examination of any existing levels and of the tract -itself. Very high, sandy or swampy ground, whether occurring at the edge -of the tract or in the middle of it, may have to be left out. The -remainder, as already mentioned, is called the commanded area. When land -occupied by houses or roads or which is very much broken, or which for -any reason cannot be irrigated, has also been deducted, the balance is -the “culturable commanded area.” - -Either before or after the culturable commanded area has been -approximately ascertained, the proportion of it which is to be irrigated -must be settled. This depends on local circumstances. In India the -supply of water is calculated on the supposition that a fraction, -generally from ¹⁄₃ to ³⁄₄, of the culturable commanded area will be -irrigated each year. The rest will be lying fallow or be temporarily out -of use or be used for crops which do not require canal irrigation. The -restriction of the area is necessary either because the supply of water -is limited or in the interests of the people. Too liberal a supply of -water tends, as already stated, to over cultivation, and exhaustion and -water-logging of the soil. - -The next step is to estimate the duty and the discharge of the canal and -then to fix its main dimensions. In Northern India the duty in the rabi -is higher than in the kharif. It may be 200 acres in the rabi and 100 -acres in the kharif. Local circumstances determine which crop has the -greater area. Suppose that it is estimated that both will be equal. Then -the total annual area for which water is to be provided must be divided -by two and this gives the kharif area. During the kharif there is -usually an ample supply of water and the kharif mean supply of the canal -is based on the kharif area and the kharif duty. The full supply is not -run all through the crop because the demand fluctuates, the demand being -greatest when all the crops have been sown and when there is no rain, -but from experience of other canals the ratio of the kharif full supply -to the kharif mean supply can be estimated. The ratio is generally about -1·25. On the kharif full supply depends the size of the channel, every -channel being constructed so as to carry a certain “full supply” or -maximum discharge and the top of the bank being made at such a height -that there shall be a sufficient margin or “free-board” above the “full -supply level.” The canal runs full provided that there is a sufficient -supply in the river or that the water level of the river is high -enough--this last condition referring to canals which have no weir in -the river--and provided also that there is a sufficient “demand” for the -water. At other times a canal runs with less than full supply. This -generally occurs throughout most of the rabi, the supply of water in the -river being then restricted. The distributaries are generally run full -or ³⁄₄ths full, some being closed, in turn, to give water to the others. -In the case of a country where there is only one crop in the year, the -average discharge of the canal can be found by dividing the area by the -estimated duty. The F.S. discharge can be assumed to bear such a -relation to the average discharge as may be found by experience to be -suitable. On some Indian inundation canals the F.S. discharge is taken -as twice the average discharge. - -The F.S. discharge of the canal having been arrived at, the alignments -of the canal and branches are next sketched out on the contour plan and -certain tracts and discharges are assigned to each branch. The gradients -can be ascertained from the levels of the country and the cross-section -of the channel can then be sketched out. If the velocity is too great -for the soil “falls” can be introduced. The above procedure will enable -a rough idea to be formed of the cost of the earthwork of the scheme. -The cost of the headworks and masonry works and distributaries can be -best estimated by obtaining actual figures for existing works of similar -character, the distributaries being reckoned at so much per mile. The -probable revenue which the canal will bring in will depend upon the rate -charged for the water and the cost and maintenance, matters which can -only be determined by local considerations based on the figures for -existing canals. - -The masonry works on a canal consist of the headworks and of bridges, -regulators and drainage crossings. The principles of design for such -works have been dealt with in _River and Canal Engineering_. It is of -course economical to make a bridge and fall in one. If the off-take of a -distributary is anywhere in the neighbourhood the fall should of course -be downstream of it. The positions of the falls should be fixed in -accordance with these considerations. If the longitudinal section is -such that the position of the fall cannot be much altered, it may be -feasible to divert a road so that the bridge may be at the best site for -the fall. In the case of a railway crossing, a skew bridge is often -necessary. In the case of a road crossing it may be feasible to -introduce curves in the road but here also a skew bridge is often -necessary. - - - - -CHAPTER II. - -THE DESIGNING OF A CANAL. - - -1. =Headworks.=--In the design of head works no very precise rules can -be laid down. Some general ideas can however be given as to the chief -points to be attended to and some general and approximate rules stated. -In every case a large scale plan of the river is of course required and -also a close examination of it and study of its character. An attempt to -forecast its action is then possible. Gauge readings for several years -and calculations of discharges are of course necessary. If the bed of -the river, in course of time, rises upstream of the weir or scours -downstream of it, a large amount of protection to the bed and banks will -become necessary. Some description of headworks and weirs, with a plan -of the headworks of the Sirhind Canal, India, has been given in _River -and Canal Engineering_, CHAPTERS IV. and X. Remarks regarding the -collection of information for such works are given in CHAPTER II. of the -same work. It is also explained how, by keeping the gates of the -under-sluices closed, a “pond” is formed between the divide wall and the -canal head so that heavy sand deposits in the pond and does not enter -the canal. By closing the canal and opening the under-sluices the -deposit is scoured away. - -The best site for the headworks of a canal depends on the stability and -general character of the bed of the river but in deciding between any -two proposed sites, the question of the additional cost of the canal, if -the upper site is adopted, has to be taken into account. Such cost may, -in rugged country, be considerable. - -In the case of Indian perennial canals, the head is often close to the -hills where the river bed is of boulders and shingle and fairly stable, -but it is often at a distance from the hills and in such cases a gradual -rise in the bed of the river, even in the absence of a weir, is more -probable than scour. Such a rise may necessitate a raising of the crest -of the weir and of the bed of the canal. - -[Illustration: FIG. 5.] - -In the general arrangement of a headworks a great deal depends on local -conditions. Sometimes the river runs in a fairly straight and defined -channel and the weir can then be run straight across it. Sometimes, as -in the case of the Ganges Canal, there is a succession of islands and -various short weirs are required in the different channels. At the heads -of the Eastern and Western Jumna Canals, the river, on issuing from the -hills, widens out (Fig. 5.) and the weir is built obliquely and not in -a straight line. Its crest is higher at the east than at the west side. -There are under-sluices at both sides. The upstream end and west side of -the island are revetted. The old head of the Western Jumna Canal, as -shown in the figure, existed long before the advent of the British, and -a temporary weir, made of gabions filled with stones, was constructed -across the river every year during the low water period and swept away -during the floods. To have carried the weir along the line shown dotted, -the head of the Western Jumna Canal being of course brought up to it, -would apparently have been feasible and cheaper, but the off-take would -have been in shallow water because of the curve in the river, and there -would have been no current along the face of the head regulator of the -canal. - -The level of the floor of the under-sluices is generally about the same -as that of the bed of the canal. The sill--made to exclude shingle and -sand as far as possible--of the canal head regulator may be 3 feet -higher and the crest of the weir 6 to 9 feet higher. The top of the weir -shutters is 1 to 2·5 feet above the F.S. level of the canal which may be -5 feet or more above the bed of the canal. If the weir is provided with -falling shutters the width of the waterway of the under-sluices may be -about ¹⁄₁₂th of the width of the waterway of the weir alone, otherwise -about ¹⁄₈th. - -In nearly all cases the weir has a flat top and flat slopes both -upstream and downstream. In a case where the river bed is of sand, the -depth of water on the crest of the weir in floods may be 15 feet and the -velocity 14 or 15 feet per second. The downstream slope of the weir may -be about 1 in 15, and the upstream slope 1 in 6. Where the river bed is -of boulders the velocity may be still higher. The faces of the weir are -usually of hammer-dressed stone. A lock for the passage of rafts is -added if necessary. - -Unless the banks of the river are high, it is necessary to construct -embankments to prevent the river water, when headed up by the weir -during the floods, from spilling over the country with possible damage -to the canal. If the river has side channels they have to be closed. The -stream may also have to be trained, by means of guide banks or spurs, so -as to remain in one channel and flow past the canal head and not form -shoals against it. Where the river is unstable, it may shift its course -so as to strike the weir obliquely and this may cause excessive heading -up at one side of the weir. In such cases it is usual to divide the weir -into bays or sections, each about 500 feet long, by “divide walls” -running at right angles to the weir. - -The free-board or height of the masonry walls and tops of embankments -above H.F. Level is about 5 feet. - -The span of each opening in the under-sluices is generally 20 to 35 -feet. The piers may be 5 feet thick. It is usual to make each alternate -pier project upstream further than the others so that long logs coming -down the river during floods, broadside on, may be swung round and not -be caught and held against the piers. - -[Illustration: FIG. 6.] - -[Illustration: FIG. 6A.] - -Figs. 6 and 6A show the headworks of the Upper Chenab Canal now under -construction (CHAPTER IV.) The site is in a low flat plain, but no -better site could be found. The weir consists of 8 bays of 500 feet -each. The crest is 10 feet above the river bed and the falling shutters -6 feet high. The slopes are 1 in 6 and 1 in 15. The bulk of the work is -rubble masonry in lime. The lower layer upstream of the crest is of -puddle; upstream of the second line of wells it is rubble masonry in -half sand and half lime; upstream of the lower line of wells it is of -dry stone and there is an intermediate layer of rubble masonry in lime -with the stones laid flat. Below the crest there is a wall of masonry 9 -feet thick and on the crest there are two strips of ashlar between which -the shutters lie when down. The extreme upstream and downstream portions -of the bed protection are of dry stone and 4 feet thick while next to -the weir are concrete blocks 2 feet thick resting on dry stone. The -width of the crest is 14 feet, of the weir 140 feet, of the protection -70 feet upstream and 110 feet downstream. The guide banks have tops 40 -feet wide and 18 and 14 feet above the crest of the weir in the upstream -and downstream lengths respectively, the side slopes being 2 to 1 and -the water slope being covered, up to H.W. level, by dry stone pitching 4 -feet thick. The left guide bank runs upstream for 3,250 feet from the -centre line of the canal and the right 2000 feet from the line of crest -shutters. The under-sluices have 8 bays of 35 feet each and the canal -head regulator 36 openings of 6·5 feet each, the large openings shown in -the figure being sub-divided. The crest of the weir is no less than 10 -feet above the river bed and the shutters add 6 feet to this. The floor -of the under-sluices is 4 feet higher than the river bed. There is thus -ample allowance for a possible rise in the river bed. - - -2. =The Contour Map.=--The contour map, besides showing the contours of -the country to be irrigated and of a strip of country, even if not to be -irrigated, which will be traversed by the main line, should show all its -main features, namely:--streams, drainages, railways, roads, -embankments, reservoirs, towns, villages, habitations, and the -boundaries of woods and cultivated lands. It should also show the -highest water levels in all streams or existing canals. A map showing as -many as possible of the above features should be obtained and lines of -levels run for the contours. In doing this, the points where the lines -of levels cut or pass near to any of the above features or boundary -lines, should be noted. It may be necessary to correct inaccuracies in -the plan or to supply defects in it. The greater the trouble taken to do -this the less will be the trouble experienced later on. - -The heights of the contour lines will, in very flat country, have -eventually to be only 1 foot apart. This will necessitate running lines -of levels half-a-mile apart at the most, and preferably 2000 feet apart, -the pegs in each line being about 500 feet apart. In less flat country -the heights of the contour lines can be further apart than 1 foot. -Whatever distance apart is decided on for them, the survey should be -done once for all. On one of the Indian canals in flat country, the -lines of levels were at first taken 5 miles apart, the branches roughly -aligned and then further surveys made. This led to great expense and -delay and the procedure has not been repeated. - -In making a contour survey, a base line, as centrally situated and as -long as possible, should be laid down, with side lines parallel to it -near the boundaries of the tract. The cross lines at half-mile or other -intervals should then be laid down. Some of them may run out beyond the -side lines. Circuits of levels should be run along the base line, the -side lines and the two extreme cross lines and be carefully checked. The -remaining cross lines should then be levelled. All the levels having -been shown on the map the contours should be sketched in. The scale of -the map for a large project may be two inches to a mile. If it is likely -that the survey will have to be extended, it will be easier to do this -by prolonging the base line and running more cross lines, than by -prolonging each of the cross lines already surveyed. This can be borne -in mind when selecting the base line. - - -3. =Alignments and Discharges.=--On the contour map the proposed -alignments of the canal, branches, distributaries, and escapes, -determined after careful consideration of all matters affecting them, -are shown. The tracts to be irrigated by each branch and each -distributary are now marked off, the “irrigation boundaries” following -approximately the valleys and lines of drainage. Any large tracts of -land which cannot be irrigated are of course shown and are excluded. -Forests or other lands which are not to be irrigated should be similarly -dealt with, otherwise confusion is likely to arise later. The commanded -area dependent on each distributary is now ascertained from the map. A -certain percentage being deducted for scattered unculturable areas the -culturable commanded areas are obtained. The proportion to be irrigated -(in India in the kharif) having previously been decided, the number of -acres to be actually irrigated by each distributary is arrived at. - -The next step is to ascertain the discharges.[9] A general duty for the -whole canal having been estimated by considering the actual figures for -other canals the full supply of the canal at its head is arrived at. -(CHAPTER I, Art. 6). In Northern India it will be the kharif duty and -kharif full supply. Since some water is lost by absorption in the -channels, the duty of the water on a branch is higher than that of the -whole canal based on its head discharge, and the duty on a distributary -is higher still. In designing a canal, an attempt has to be made to -estimate the losses of water in the main canal and branches, so that the -duties of the branches and distributaries may be estimated and the -channels designed accordingly. On the Western Jumna Canal the figures -were estimated to be as follows:-- - - Kharif. Rabi. - Average discharge at canal head (c. ft. per sec.) 3536 2755 - Duty based on the discharge (acres) 98 138 - Estimated loss of water in canal and branches (c. ft. per - sec.) 400 300 - Average discharge at distributary head (c. ft. per sec.) 3136 2455 - Duty based on the discharge (acres) 111 154 - - [9] In this Article and in the rest of this Chapter it is assumed that - the canal is a Northern Indian one. Any modifications necessary to - suit canals in other countries will readily suggest themselves. - -The question of duty is one which if not carefully considered, may cause -some confusion. A canal and branches, having been designed with certain -assumed duties and with discharges based on certain values of N in -Kutter’s co-efficient, have, let it be supposed, been constructed to a -greater or less extent. When the time comes for constructing the -distributaries, the engineers concerned may have different ideas, based -on later experience, as regards the probable duty and the most suitable -value of N. If they design the distributaries with a higher duty and a -lower value of N, it is obvious that they can provide more -distributaries than at first designed, or can increase their lengths. In -either case they would provide for an increased commanded area. If they -do not do this, they ought to adhere to the values at first proposed, -thus making the channels larger than, according to their ideas, would be -necessary. These larger channels will be able to do more irrigation, by -an increase, not in the commanded area, but in the proportion of it -which is irrigated. Any other course would result in the canal carrying -more water than could presumably be used by the distributaries. Again, -the question how the assumed duty was arrived at may need consideration. -It may have been arrived at by taking the duty figures of some existing -canal, based on discharge figures which were the result, not of observed -but of calculated discharges, and if the calculations were based on a -value of N which experience has proved to be wrong, a correction is -obviously needed. Many mistakes of the kinds indicated above have been -made, not perhaps in the case of a project which has been recently got -up and is then quickly carried out in its entirety, but in one which is -carried out slowly or after a long period has elapsed or in one which -consists of extensions of an existing system. So great, however, is the -elasticity of a channel--by which is meant its capacity for adapting -itself to varied discharges, a small change in the depth of water -causing a great change in the discharge--and so considerable has been -the uncertainty as to the real duty to be expected, that any mistakes -made have not usually resulted in any serious trouble. - -[Illustration: BIFURCATION AT TAIL OF CANAL. - -The Distributaries have Gates and Winches. - -_To face p. 41._] - -It has been stated (CHAPTER I, Art. 2) that it is not desirable to let -one channel tail into another. In old canals a distributary used -sometimes, after running parallel to a canal, to be brought back towards -it and tail into it. The advantage of this was that the distributary had -not to be made very small towards the tail and that, if the demand -abruptly ceased, the distributary was not likely to breach. The -principle was, however, essentially bad. The lower part of the -distributary was obviously too near the canal and not centrally -situated as regards the irrigated strip. The portion at the extreme tail -was superfluous. Again, whatever volume of water was carried through the -distributary and back into the canal, was needlessly detached instead of -being kept in bulk. Moreover the duty of water on such a distributary -cannot be ascertained without a tail gauge and the observation of -discharges at the tail. There are similar objections to one distributary -tailing into another. Each should be separate and distinct. - -A major distributary is one whose discharge is more than 40 c. ft. per -second. It may be as much as 250 c. ft. per second. A branch, as soon as -it reaches a point where its discharge becomes only 250 c. ft. per -second should be considered as a major distributary. A minor -distributary is one whose discharge is from 8 to 40 c. ft. per second. A -minor distributary is nearly always a branch of a major distributary. -There are instances of “direct minors,” i.e., minors taking off from -canals or branches. Such a minor, unless its discharge is a large -fraction of that of the canal which supplies it--and this can seldom be -the case--is objectionable because the petty native official who has to -see to the regulation of supplies can manipulate the supply easily and -without detection, and the number of persons irrigating from it being -small, he can make private arrangements with them. On the Sidhnai Canal -there are some half-dozen distributaries each of which had one or two -minors which took off close to the head of the distributary. The people -who irrigated from the minors managed to get the heads shifted and taken -off direct from the canal, on the ground that, the water level in the -canal being higher than in the distributary, there would be better -command and less silt deposit. The irrigation on all these minors ran up -to a figure far in excess of what had been intended, to the detriment of -lands further down the canal. The minor heads have all been -retransferred to the distributaries, the difficulty as to command being -got over, as it should have been at first, by constructing weirs in the -distributaries. The fall in the water surface at the distributary head, -i.e., the difference between the water level in the canal and that in -the distributary downstream of its head but upstream of the weir, is -quite trifling or even inappreciable. - -In some of the older Indian canals it was the custom to place the heads -of distributaries, not just above a fall but several hundred feet above -it, the idea being that the distributary then received less silt. This -practice has now been discontinued. There is no valid reason for -following it. - -The question whether, when a channel crosses a road on the skew, a skew -bridge should be constructed or curves introduced into the road or -channel, is one which requires some consideration. As far as possible -the lines of channels should be fixed so as to cross important[10] roads -on the square or with a small angle of skew. In the case of main canals -or branches, the introduction of special curves is generally out of the -question, but if the road is not straight something can be done by -shifting the line one way or the other. In the case of “major” -distributaries, curves can to some extent be introduced. In the case of -“minor” distributaries it is often possible to curve the channel, with a -radius of say 500 feet, so that it will cross the road at right angles. -There is very little objection to a skew bridge if the angle of skew is -not great. The angle of crossing having been made as near to 90° as -possible, the bridge can be made skew though not necessarily so much -askew as the road. Slight curves can be introduced into the road. When -the road is made askew, a bridge on the square involves at least three -considerable curves (Fig. 7) and the taking up of extra land. It also -causes, in perpetuity most likely, a more or less inconvenient and -unsightly arrangement and one which, in most countries, would not be -tolerated. When the angle of skew is not great, it is best to introduce -no curve at all into the road. In the case of a “village” road, which -may be more or less undefined and liable to be shifted, the difficulty -about land may not be great, but even in this case the angle of crossing -should, if possible, be kept near to 90°, especially in the case of -minors, and where curves have to be introduced into the road they should -be suitable ones. Abrupt angles are not only unsightly but are unfair to -the cart drivers. The crossings of village roads by the minors of a -certain great modern canal have been stigmatised as “hideous.” Indian -canals can afford to do work properly. - - [10] In India “district” and “provincial” roads. - -[Illustration: FIG. 7.] - - -4. =Remarks on Distributaries.=--Before a canal system can be properly -designed, it is necessary to determine certain points in connection with -the working of the distributaries. A distributary is intended to -irrigate a certain kharif area. Its average kharif supply is determined -from the assumed kharif duty. It generally runs full in the kharif but -not always. In a very dry tract such as the Montgomery district of the -Punjab, the demand is so great and so steady that a distributary -practically runs full through the greater part of the kharif. In such a -case the canal or branch must be so designed that it can keep all -distributaries full at the same time. Its F.S. discharge will be the sum -of all the F.S. discharges of the distributaries plus the losses of -water by absorption. - -But in other cases, especially if the rainfall is considerable, a -distributary does not require its full supply, either all through the -kharif or for long at a time. An estimate must then be made of what it -will require. It may be estimated that its requirements will be met if, -during the period of greatest demand, it is closed for two days out of a -fortnight and receives full supply for the remaining twelve days. In -this case, since the various distributaries need not all be closed on -the same days, the canal or branch can be so designed that it will carry -a full supply equal (after deducting losses) to ⁶⁄₇ths of the aggregate -full supplies of the distributaries. In other cases the fraction may be -³⁄₄ths. It is likely to be lower the greater the rainfall of the -district. Even in the case when the distributaries run full through -nearly the whole of the kharif, there will be periods when they only run -with about ³⁄₄ths full supply. If full supply were run at such times, -many of the outlets would discharge more water than was required, the -cultivators would partly close them, and breaches in the banks of the -distributary might result. Thus the water level of a distributary must -always be so arranged that it will have a good “command” when it is -running with about three-fourths of the full supply discharge. The water -level with ³⁄₄ths full supply is generally ·5 to ·75 feet below the full -supply level but it should be calculated in each case. Generally it will -be correct to make the water level, when ³⁄₄ full supply is run, about 1 -foot above the high ground traversed by the distributary, excluding any -exceptionally high portions of small area. A more exact method is given -in Art. 9. The greater the proportion of the culturable area which is to -be irrigated, the less should be the area of any high land which is -excluded. The F.S. levels of the distributaries at their off-takes must -be settled in accordance with the foregoing remarks, and these F.S. -levels must be entered on the plan. Neglect to thus fix the F.S. levels -of distributaries before designing the canals has frequently led to -trouble. - -The head needed at a bifurcation in order to get the supply into a -branch or distributary is always small unless the velocity is high. For -a velocity of 3 feet per second the head required is only about ·16 ft., -for 2 ft. per second ·1 ft. - -On an Inundation Canal which has no weir across the river, the mean -supply downstream of the regulator (which is built a few miles down the -canal lest it should be damaged by the shifting of the river) is, as has -been mentioned, about half the full supply. The command in such canals -is not generally very good. A distributary can often obtain only mean -supply and it should be designed so as to command the country when it is -carrying mean supply. A detailed description of Inundation Canals in -Northern India, is given in _Punjab Rivers and Works_. - -Let M, F, m, f, be the mean and full supply discharges at the heads of a -canal and of an average distributary on it and let the number of -distributaries be n. It has been seen (Chap. I. Art. 6.) that M = ·8F -about. Let k be the proportion of the supply lost by absorption in canal -and branches. Then n m = (1 - k) M = ·8 (1 - k) F. If the distributaries -all run with full supplies--at the time of greatest demand--for 4 days -out of 5, then, - - nf = 1·25 (1 - k)F - - f 1·25 - - = ---- = 1·56 - m ·8 - -Since k depends on the wetted area, it is not likely to be so great for -F as for M, but the above gives a general idea of the ratio of the full -kharif discharge to the mean kharif discharge. On a large canal the -circumstances of the distributaries will not all be similar. Some will -run full for a greater proportion of their time than others. They can be -divided into groups and the ratio of the full to the mean supply -calculated for each group. The mean supply is, as above stated, obtained -from the area to be irrigated, and the duty as estimated at the -distributary head. - -At one time a system was introduced of making distributaries of large -size with the idea of running them for short periods. One reason given -for abandoning this arrangement, was that there was a tendency to run -such a distributary for too long. This reason is not very intelligible. -It would be applicable to any distributary which was not intended to be -run without cessation. The result would be that some other distributary -would be kept short of water and this would imply extremely bad -management. The chief reason against such a distributary is the greater -cost of its construction. It would effect a saving of water. The ratio -of the discharge to the wetted area would be high, though this would be -to some extent neutralized by the greater frequency of closures, since, -when water is admitted to a dry channel, the absorption is at first -great. There would also be some difficulty in the distribution of the -water because of the short period for which it would remain open. It -will be seen (Chapter III. Art. 5), that it is desirable to open and -close always at the same hour of the day. An ordinary distributary might -run for 11 days out of 14. One of double the size could not conveniently -be run for 5¹⁄₂ days. A distributary can always be enlarged if -necessary, but if made too large it is extremely difficult to make it -smaller. - -It was also, at one time, usual to make minors, when there were several -on a distributary, of large capacities so that they ran in turns. The -preceding remarks apply to this case. The system has been abandoned. - - -5. =Design of Canal and Branches.=--The apportioning of discharges to -the various channels having been effected as described in Art. 2, the -designing of the canal and branches is proceeded with. Rough -longitudinal sections of all the lines are prepared by means of the -contour map, the ground levels being shown at intervals of one foot--or -whatever the vertical distance between the contours may be--and the -horizontal distances obtained from the map by scaling. - -On these longitudinal sections the lines proposed for the bed and F.S. -levels are shown reach by reach and also the mean velocities and -discharges. - -The laws of silting and scouring and the principles on which channels -should be designed are fully gone into in _River and Canal Engineering_. -It is there explained that, for a channel of depth D, there is a certain -critical velocity, V₀, which just prevents the deposit of the silt, -consisting of heavy clay and fine sand, found in Indian rivers--this -silt enters the canal in such immense quantities that the canal silt -clearances would be impossible if much of it was deposited in the -channels--that sand of grades heavier than [·1] may deposit in the head -of a canal and well nigh threaten its existence, that the clear water -entering the canal in winter may pick up and carry on some of the sand -but that proper steps for preventing the deposit in the canal can be -taken at the headworks. This last question has been referred to in Art. -1. The following additional rules for designing canals in Northern India -are chiefly taken from those given by Kennedy in the explanatory notes -to his Hydraulic Diagrams, which are in use in the Irrigation Branch in -Northern India. - - (1) Near the hills where the bed is of shingle the velocity may exceed - V₀. A few other soils will stand 1·1 V₀. - - (2) In ordinary channels any excess over V₀ will give much trouble - lower down. - - (3) In the first four or five miles of a distributary, V₀ should be - allowed and gradually be reduced to ·85 V₀ at the tail, the gradient - being reduced if convenient, while a minor or branch distributary - should have less than V₀ at its off-take and still less at the tail. - The sand is drawn off by the outlets and in the lower part of a - distributary it is often non-existent. - - (4) If there is efficient silt trapping at the head of the canal any - figures arrived at by the preceding rules should be multiplied by ·9. - - (5) In the case of a canal having its head far from the hills, the - sand is finer and any figures arrived at as above may be multiplied - by, perhaps, about ·75, but further experience is needed to decide - this. - - (6) If the soil is very poor, especially if the depth of water is more - than 6 or 7 feet, the velocity should be less than V₀--say ·9 V₀--so - as not to cause falling in of the banks. Depths of more than 9 or 9·5 - feet should, as far as possible, be avoided for the same reason. - - (7) At a bifurcation, one branch channel may have no raised sill, and, - owing to its smaller depth, it may draw off no surface water and get - an undue share of rolling sand. Its velocity should be greater than V₀ - and that of the other branch be less than V₀. - - (8) At such a bifurcation it may be necessary, during times of low - supply, to head up the water in the main channel and some silt may - temporarily be deposited in it. When the heading up ceases, the silt - is scoured away but it mostly goes into the branch whose bed level is - the lower. It is best to design such bifurcations so that the sill - levels of the two branches are equal and, if possible, so that their - bed levels are equal.[11] Otherwise the channel which is likely to get - most silt should have the steeper gradient. - - (9) Any existing well established régime should not be tampered with. - - [11] Appendix A in _River and Canal Engineering_ deals with some - instances of fallacies in questions concerning flow in open streams. - An extract from it describing a remarkable divide wall recently - constructed at the head of the Gagera branch, Lower Chenab Canal, is - given in Appendix A of this book. - -Experience shows that in designing Irrigation Channels in the plains of -India in accordance with Kennedy’s figures, the maximum ratio of bed -width to depth of water is as follows:-- - - Discharge, c. ft. per second 10 25 100 200 500 1,000 - Ratio 3·5 4 4·5 5 6 6 - -The actual gradients of the canals generally range from about 1 in 8,000 -for a main canal to 1 in 2,000 for the tail of a distributary, but near -the head of a canal where the bed is of boulders and shingle, the -gradient may be as steep as 1 in 1,000.[12] The velocity in this last -case may be 5 feet per second but generally it is not more than 3 or 4 -feet per second in canals and branches, and 1 to 2 feet per second in -distributaries. - - [12] On the Upper Jhelum Canal, 1 in 970. - -In designing the channels, N, in Kutter’s co-efficient, may be taken as -·0225 or ·020, according to judgment. For new and smooth channels ·020 -is generally correct. A channel generally becomes rougher by use but -sometimes it becomes smoother. Cases have occurred in which N has been -found to be ·016. This question is discussed in _Hydraulics_, Chap. VI. - -The bed width of a canal is reduced, where a distributary takes off, in -such a way that when the canal and distributary are both running full, -the depth of water in the canal continues to be uniform and the flow to -be uniform. When the distributary is closed there is heading up in the -canal upstream of the off-take, but not enough to make any appreciable -difference unless the capacity of the distributary is a large fraction -of that of the canal and even then no harm is likely to result. - -The preceding rules and principles being taken into consideration, the -channels are designed. The bed levels, gradients and depths are so -arranged as to give the velocities suited to the soil and to maintain -the proper relation of depth to velocity. The bed width is arranged so -as to give the proper discharge. The full supply level of the canal and -branches has also to be so arranged that it shall be higher, at each -distributary off-take, than the full supply level of the distributary. -It is desirable to be able to give a distributary its full supply even -when the canal is low. Generally the slope of the country along any line -is greater than would be suitable for the bed, and “falls” are -introduced. The off-take of a distributary is generally just above a -fall and there is generally an ample margin between its F.S. level and -that of the canal. The discharge of the canal during the greater part of -the rabi may be only about half the full supply. This discharge should -be estimated and the water level corresponding to it calculated and -shown on the longitudinal section. If possible the levels should be so -arranged that even with its least supply the water level in the canal -will enable full supply to be given to a distributary. If this cannot -otherwise be managed it may be necessary to construct a regulator in the -canal below the head of the distributary so that, during low supplies, -the water can be headed up. It has been stated in _River and Canal -Engineering_, Chapter IV., that such heading up, if temporary, is not at -all likely to cause silt deposit in the canal. The designing of the -distributaries is not proceeded with at this stage. - -Since no irrigation is usually done directly from the canal and -branches, they are designed without any particular connection between -the level of the water and that of the country traversed. Dangerously -high embankments are of course avoided as far as possible. The bed is -designed at such a level that the excavation and embankment at any place -will be, as nearly as possible, equal. Land in India is cheap. When the -excavation exceeds the embankment the balance is made into a spoil bank. -When the excavation is less than the embankment the balance is got from -borrow-pits. - -The side slopes of channels in excavation are generally 1 to 1, in -embankment 1¹⁄₂ to 1. The sides of channels of small or moderate size -usually become about ¹⁄₂ to 1, or even vertical, by the deposit of silt -on the slopes. This reduction of area is allowed for in the design i.e. -the bed width is so designed that the channel will carry the required -discharge, not with the side slopes as executed, but when they have -become ¹⁄₂ to 1. In large canals however the sides do not always silt up -but rather tend to fall in. When this is expected to occur the allowance -above described is not made. Berms are left so that if any part of the -sides fall in, the bank will not also fall in. The berms also allow of -the channel being widened if that ever becomes necessary. Type sections -are given in Figs. 8 and 9. - - -6. =Banks and Roads.=--Figs. 8 and 9 show the banks and spoil. - -[Illustration: FIG. 8.] - -[Illustration: FIG. 9.] - -The scale is 6 feet to an inch. The depth of water, in this particular -case, is 7 feet, and the bank, excluding the small raised bank, 2 feet -above the water. The inside edge of the bank, where the small raised -bank is shown, is kept parallel to the canal for a considerable -distance. Its position is got by drawing a line, shown dotted, at, -generally, 1¹⁄₂ to 1. The embanked part of the slope is actually made at -1¹⁄₂ to 1, but the excavation is at 1 to 1, so that a berm is left. The -width of this berm of course varies as the depth of digging varies. If -there is likely to be much falling in of the sides the berm can be made -wider, the dotted line starting, not from the edge of the bed, but from -a point further in. On an inundation canal in sandy soil the berm may be -20 feet wide. In figure 8, the inside slope above the berm is supposed -to have silted up to a slope of 1 to 1. In cases where it is expected -the whole inside slope will silt to ¹⁄₂ to 1 the dotted line, to give -the edge of the bank, can be shifted towards the channel so that the -berm at the ground level when the channel is excavated will be very -small for the minimum depth of digging. There is no need for the inner -edge of the bank to run parallel to the canal for great distances. Its -position can be shifted whenever suitable and the width of the berm at -ground level varied. This prevents the occupation of a needlessly great -width of land. It used at one time to be not unusual to make a bank with -a berm on the land side, similar to that formed by the spoil in Fig. 8, -but at about the level of full supply in the canal. The principle is not -a good one. Salient angles are liable to be worn away. If earth has to -be added to a bank to strengthen it, the whole can be widened or the -rear slope flattened. The roadway is shown 18 feet wide, which is nearly -the maximum. For the drainage of rain water it has a transverse slope, -away from the canal, of about 1 in 50. The small raised bank on the -canal side is to give safety to wheeled vehicles. It is provided on the -patrol bank[13] on main lines and places where there is much traffic or -where there is plenty of width of bank to spare. When the ground level -is, for a considerable distance, above the proper bank level--which is -at a fixed height above the F.S. Level--so that the road and its -side-drain have to be cut out, much earthwork can be saved by allowing -them to be at a higher level and, in the case at least of the non-patrol -road, giving the road a reduced width. - - [13] A canal has an unmetalled driving road--called the “patrol road” - or “inspection road” on one bank. This road is reserved for the use of - officials. Otherwise, it would soon be cut up and worn away, and the - cost of repairs would be excessive. The patrol road should be on that - bank which is, in the morning (the time when inspections are usually - made) in the shade of trees planted on the landward side. Trees are - not usually planted near the water edge as they are sometimes blown - down. In Northern India the canals generally flow in a southerly - direction, so that the left bank is best for the patrol bank. On the - other bank there is a bridle road which is open to the public. Near a - rest house--unless there is a bridge actually at the place--the patrol - road should be on the same bank as the rest house. It can if necessary - cross at the first bridge. Frequently there is also on one or both - sides of the canal a “boundary road,” which is open to the public, - along the toe of the outer slope. Along a distributary there may be a - boundary road on one side. It is generally the only road which can - take wheeled traffic, and in this case it should be reserved for - officials unless money is provided to keep it always in repair. - Officials have to be on tour for weeks or months at a time, and in all - weathers. Their baggage carts also have to precede and follow them. - Anything which facilitates their touring about and seeing things for - themselves is, in India, most desirable. At a watercourse crossing the - boundary road along a distributary should be taken by a curved incline - up on to the bank and down again. Thus not only is the cost of a - culvert saved, but any touring official who is driving obtains a view - of the channel which he cannot get from the boundary road. - -[Illustration: FIG. 10.] - -In shallow digging, the plan of setting back the banks (Fig. 10) and -letting silt deposit as shown by the dotted lines, is one which should -be followed much oftener than it is. It not only gives eventually a very -strong bank, but it enables the borrow pits, from which the earth for -the banks is got, to be dug inside the banks. Outside borrow pits, -besides being a source of expense, owing to compensation having to be -paid to those in whose land they are dug, cause great areas of hollows -which are not only unsightly, but are often full of stagnant water and -are thus a fruitful source of mosquitoes and malaria. Insufficient -attention has hitherto been paid to this matter. - -In designing each reach of a canal or branch, type cross sections should -be drawn out for several different depths of digging, _e.g._, one for -very shallow digging, _i.e._, where the bed is little, if at all, above -the ground level, one for deep digging where the ground is higher than -the water level, and one for the “balancing depth,” where the area of -the channel excavation is equal to the earth required for the banks. In -calculating the earthwork the sectional area of the digging or of the -embankment is taken, whichever is the greater. - -The proper width and height of bank for any channel depends partly on -the maximum depth of water in the channel, and partly on the discharge. -Given a depth of water of say 8 feet, a breach will obviously be more -disastrous with a great volume of water than with a small volume. The -following statement gives some figures suitable to the rather light and -friable soils of Northern India, but the question is largely one of -judgment. Generally a low and rather wide bank is preferable to a higher -and narrower one. If a road, with or without the small raised bank next -the canal, is required, special widths can, of course, be arranged for. -A 14-foot bank is required for a driving road. - - ------------+--------------+---------------+--------------- - Top Width of|Height of Bank| Greatest | Greatest - Bank. | above F. S. | Admissible | Admissible - | | Discharge. |Depth of Water. - ------------+--------------+---------------+--------------- - Feet. | Feet. |C. ft. per sec.| Feet. - 20 | 2 | 12,000 | 12 - 18 | 2 | 8,000 | 12 - 16 | 2 | 5,000 | 11 - 14 | 2 | 3,000 | 10 - 16 | 1·5 | 2,000 | 9 - 14 | 1·5 | 1,500 | 9 - 12 | 1·5 | 1,200 | 8 - 10 | 1·5 | 1,000 | 7 - 9 | 1·5 | 700 | 6 - 8 | 1·5 | 500 | 5·5 - 7 | 1·5 | 400 | 5 - 6 | 1 | 300 | 4·5 - 5 | 1 | 200 | 4 - 4 | 1 | 100 | 3·5 - 3 | 1 | 50 | 3 - ------------+--------------+---------------+--------------- - -The spoil in Fig. 8 is shown at a different level from the bank proper, -as it should be to give a neat straight edge to the bank. The width of -the spoil may vary every chain. In Fig. 9 the spoil is raised to avoid -taking up too much land. The spoil presents the best appearance when its -height is kept uniform for as long a length as possible, the width -varying according to necessity, When the height has to be altered, the -change should be made by means of a short ramp. When the spoil is higher -than the road, gaps in it are left at intervals so that rain water can -pass away. When the spoil is heavy for a very short length it can, in -order to avoid a short and unsightly heap, which would result from the -adoption of the section shown in Fig. 9, be placed as in Fig. 8, some of -it being led askew. - -The small channel shown outside the bank in Fig. 8 is a watercourse for -enabling trees to be grown. It has, of course, to be graded, and it may -be in cutting or in embankment. If any silt clearances of the canal are -likely to be necessary, the watercourse must be set back to allow room -for the spoil. Such spoil, if sandy, is to a large extent washed down or -blown away and does not accumulate to anything like the extent that -would be expected.[14] Moreover the spoil can extend onto the -watercourse when the trees have grown big, and no longer need watering. -Outside the watercourse is shown the boundary road and the land boundary -pillar. The small channel in Fig. 9 is a drain for rain water. It can be -used as a plantation watercourse if the water is lifted. - - [14] This fact has been quoted (_The Pioneer Mail_, “Silt,” 8th March, - 1913) as showing that the silt supposed to be cleared is not really - cleared. This may be the case to some extent, but shortage of spoil is - little proof of it. - -Where there is no spoil, some extra land, perhaps 20 feet on either -bank, is usually taken up for getting earth from for repairs. - - -7. =Trial Lines.=--The proposed lines of channel, determined as -explained in Art. 5 should next be laid down on the ground. A line -should consist of a number of straight portions. The curves should not -be put in. Trial pits should be dug at intervals. Some defects in the -line may at once become apparent because the contour map, owing chiefly -to the lines of levels having been taken a considerable distance apart, -is not perfect. A line may pass through a patch of very high or very low -ground or too near to some building or other object with which it is -desirable not to interfere. Alteration may be desirable at a drainage -crossing or at the off-take of a branch. The lines should be corrected -where necessary. Sometimes the corrections may be very considerable. -Allowance can be made for the alterations which will occur when the -curves are laid out. Where there is doubt as to which line is the best, -trial pits may be dug to obtain further information regarding the soil. - -The line should now be levelled, careful checks being made, a -longitudinal section of it prepared and the proposed bed, bank and F.S. -level shown. The ground levels ascertained by levelling the line, are -certain to disagree, to some extent, with the contour lines. The latter -were got only by inference from the levels of points in the survey -lines, and they should be corrected in accordance with the fresh levels -now available. If the line does not seem to be the best that can be got, -a fresh line can be marked on the plan and the above procedure repeated. - - -8. =Final Line and Estimate.=--As soon as the best line seems to have -been found, a large scale plan of the country along its course should be -made by taking bearings or off-sets from points in it to the various -objects and noting where the line cuts them. On this plan will be shown -the exact alignment, the curves being put in and the straight portions -slightly shifted where necessary so that the line may pass at a proper -distance from any buildings or other objects. But before this procedure -is carried out, or while it is being carried out, the estimate for the -work can be prepared from the longitudinal section already taken. Such a -section is of course amply sufficient for a “project estimate,” in which -only approximate figures are given, and it is quite near enough for any -estimate. In the case of small works which have often to be executed -with great promptitude, lamentable delays have occurred owing to the -engineer deferring the preparation of his estimate till he had got the -line exactly fixed. Moreover there is a chance of the labour being -thrown away in case the sanctioning authority directs any change in the -alignment to be made. - -In the case of a large scheme, a project estimate is prepared. In this -the earthwork and the area of land to be occupied are calculated pretty -accurately. Designs and estimates are also prepared for the headworks -and for the chief regulators. For works of which there are to be many of -one type--bridges, falls, distributary heads and small drainage -syphons--the cost is arrived at from lump sum figures, one drawing of -each kind being submitted as a type. The distributaries are -approximately estimated at mileage rates. In the case of a small scheme -everything is estimated in detail except perhaps the distributaries or -some of them. - -[Illustration: CANAL WITH BRIDGE AND DISTRIBUTARY HEAD. - -The Head has Gates and Winches. - -_To face p. 61._] - - -9. =Design of a Distributary.=--A distributary is a canal in miniature -and, like a canal, it may have branches. It has masonry bridges, falls -and drainage syphons. It has, as already mentioned, a masonry regulator -at its head. At the off-take of any branch or distributary there is a -regulator in the head of the branch. If the branch takes off a large -proportion of the water there is a double regulator. A distributary -gives off watercourses as a canal gives off distributaries. The -watercourses belong to the people and not to Government and they are -cleared and maintained by the people. Each watercourse has a masonry -head known as an “outlet” (Fig. 11). The outlet is the point where -the water passes from the hands of Government officials to those of the -cultivators. The outlet is of masonry and its opening is not adjustable -but is fixed in such a way that its discharge, when the distributary is -full, bears, as nearly as can be arranged, the same ratio to the F.S. -discharge of the distributary as the area intended to be irrigated by -the watercourse bears to that intended to be irrigated by the -distributary. - -[Illustration: FIG. 11.] - -The floor of the outlet is level with the bed of the distributary. It -thus draws off rolling sand which might otherwise accumulate in the -distributary. Small outlets are made of earthenware pipes, about ·4 feet -in diameter, laid in concrete. Two pipes, or three, may be laid side by -side. If more than three would be required, a masonry opening is -adopted. The discharge through an outlet, is generally 2 to 5 c. feet -per second per square foot of outlet area, and the head ·1 to ·5 feet. - -For the tract of country allotted to any distributary, a contour map is -prepared on a fairly large scale, say 4 inches to a mile. On the map -the line is laid down and a rough longitudinal section, showing the -ground level, is prepared as in the case of a canal. - -It has already been stated (Art. 4) that a distributary is so designed -that its water level, when three-fourths of the full supply is run, -shall be well above the level of most of the ground along its course. In -other words it should have a good command. A good rule is to allow a -fall of ·5 feet from the level of the water in the distributary to that -in the watercourse, a slope of 1 in 4,000 for the water flowing along -the watercourse, and a fall of ·3 feet for the water at the tail of the -watercourse to the level of the ground. This last level is, like the -other ground levels, taken from the contour map. This procedure, in -short, consists in making the water level of the watercourse at its head -govern that of the distributary, just as the water level in the -distributary at its head was made to govern that in the canal. - -The enlarged contour map of the distributary area shows, among other -things, the boundaries of the lands belonging to each village. Generally -a watercourse supplies water to only one village. When, however, a -village is far from the distributary, its watercourse has to pass for a -long distance through other villages and it would be wasteful of water -to have two separate watercourses. In such cases one watercourse may -serve two villages or more. When a village is near to the distributary -and its land extends for a long distance parallel to the distributary, -it may have several watercourses for itself alone. A watercourse can -generally be most conveniently dug along the boundary line of two -villages, or there may be some other line which the people particularly -desire.[15] Subject to, or modified by, these considerations a -watercourse is designed to run on high ground like a distributary. - - [15] They also frequently wish the “chak”--the area irrigated by a - watercourse--so arranged that two men who are “enemies” shall not be - included in the same “chak.” This condition can be complied with only - up to a certain point. Arrangements may be modified but not in such a - way as to upset the proper rules. - -[Illustration: CONTOUR MAP (PART) AND LINE OF DISTRIBUTARY. - -The scale is 1 inch to 2 miles. The contour lines at 1 foot intervals -are shown dotted, the roads by double lines. The line of the -distributary, in order to follow the ridge of the country, would have -gone more to the left of the plan near the village. The shifting of the -line to the right brings it nearer to the centre of the irrigated -tract--supposed to be the whole area shown--and enables a single bridge -to be built at the bifurcation of the two roads. Suitable lines for main -watercourses are shown in thin firm lines. It is assumed that the -command is sufficient to enable the watercourses to run off at the -considerable angles shown. - -_To face page 63_] - -The great object is to reduce the total length of channels, _i.e._, -minors and watercourses. No watercourse can be allowed to run alongside -of or near to another. It may run alongside a canal or distributary when -really necessary to gain command but not otherwise. The longer the -watercourse the larger the chak. The discharge of an outlet may be -anything up to 4 or 5 c. feet per second. This limits the size of a -chak. If a chak is too big it can be split up or a minor can be -designed. Very small chaks are to be avoided, but it is difficult to fix -a minimum size. The irrigation boundary of the distributary, as fixed in -the project, is shown on the map but in practice it will not be exactly -followed. For various reasons the boundaries of a chak may run somewhat -outside it or stop short of it. - -Where a distributary gives off a minor and there is a double regulator, -watercourses should, as far as possible, be taken off from one or other -of the branch channels and not from upstream of the double regulator. -Otherwise, irregularities are likely to occur, both of the regulators -being partially closed at the same time--a thing which is never -necessary in legitimate distribution of the supply--in order to head up -the water and increase the discharges of the outlets. - -A watercourse nearly always gives off branches and generally a system of -turns is arranged by the farmers among themselves, each branch in turn -taking the whole discharge of the watercourse for a day or part of a -day, the other branches being closed by small dams of earth. To irrigate -a field alongside the watercourse a gap is cut in its bank. For fields -further away, smaller channels run off from the watercourses at numerous -points. Several gaps and several field channels may be in flow at one -time, and there is a dam in the watercourse below the lowest one. - -Occasionally, on an old canal, one watercourse crosses another, the -lands irrigated being at different levels, but such crossings do not -often occur in systems of watercourses laid out according to modern -methods. They are, however, quite legitimate. - -The lines of the main watercourses are sketched on the map, their -irrigation boundaries shown on it, and F.S. discharges allotted to them -according to the areas which are to be dependent on them. In order that -this may conveniently be done the “full supply duty” or “full supply -factor” for the distributary is obtained. It bears the same ratio to the -ordinary duty that the mean supply bears to the full supply. The total -of the F.S. discharges of all the watercourses should, with an allowance -for loss by absorption in the distributary, be the same as the F.S. -discharge of the distributary. If the results are very discrepant it -shows that the sizes of the outlets need revision. Possibly they may all -be too large. - -In “colonization” schemes where a canal is constructed to irrigate waste -lands--which are the property of Government and which are divided into -square blocks and given out to colonists--Government has complete -control of the watercourse system, and can arrange it exactly as -desired, but in other cases landowners often strenuously oppose the -passage of watercourses through their lands. Compulsory procedure -according to legal methods is tedious, but the practical rule is not to -let anyone have water until any watercourses which are to pass through -his land have been not only agreed to but constructed. - -In ordinary cases Government possesses no power as to the precise line -on which a watercourse is dug. It fixes the site of the outlet and -assigns certain land to it, and sketches out the line of the -watercourse. If the people choose to alter the line they can do so, but -great alterations in the main watercourses are not generally feasible. - -The positions of the outlets[16] having been settled after discussion -with the cultivators, a table is prepared showing the chainage of the -outlets, the probable head or difference between the F.S. level of the -distributary and of the watercourse, and the F.S. discharge. From this -the sizes of the outlets are calculated and shown in another column. If -the length of the outlet barrel is not more than 5 or 6 times the -diameter--in the case of a barrel whose cross section is not round or -square, the mean diameter--the discharge can be calculated as for a -“short tube,” but if longer the formula for flow in pipes should be -used, allowance being, of course, made for the head lost at the -entrance. The outlets generally consist at first of wooden “shoots” or -long tubes, rectangular in cross section. This is because, after they -have been tested by a year or two years’ working, the sizes nearly -always require adjustment and the cultivators often wish to have the -site shifted. - - [16] The positions can be slightly altered by the Engineers for any - sufficient reason. - -[Illustration: FIG. 11.] - -The uncertainty as to the proper size of an outlet is due to several -causes. If the command is very good there may be a clear fall from the -outlet into the watercourse. In this case the discharge depends only on -the depth of water in the distributary, and is known pretty accurately. -But ordinarily the outlet is submerged, and its discharge depends on the -difference between the water levels in the distributary and in the -watercourse. The latter level is not fixed. The cultivators can lower -it, to an extent which depends chiefly on the distance of the fields -from the distributary, by deepening or widening the watercourse. In this -way the discharge of the watercourse is increased except when a dam is -temporarily made in it for the purpose of irrigating any comparatively -high land. This uncertainty as to the discharge can in some cases be got -over by building a cistern (Fig. 11). This has the same effect as -raising the level of the barrel, the real outlet being no longer -submerged, and the discharge depending on the depth of the crest of the -overfall below the water in the distributary. But such cisterns add -greatly to the cost of an outlet, and they can only be adopted when -there is good command. A great cause of uncertainty as to the proper -size of an outlet is the variability of the duty of the water on the -watercourse. The soil may be clayey or sandy, the watercourse may be -short or long, the crops grown may be ordinary ones or may be chiefly -rice, which requires three or four times as much water as most other -crops, and the cultivators may be careful or the opposite. Again, the -people may, if the outlet gives a plentiful supply, often keep it -closed, but there is no record of such closures nor would the people -admit that they occur. These causes may all operate in one direction--on -a whole distributary this cannot happen to the same extent--and thus -enormous differences in duty may occur. There is no way of arriving at -the proper size for an outlet except trial. Observations of the -discharges of the outlets are of very limited use. The discharge may -vary according to the particular fields being irrigated. Observations of -discharges will be useful in cases where the people complain, or when -the discharge is obviously much greater or much less than intended and -will in such cases enable temporary adjustments to be made, but by -placing a dam in a watercourse and turning the water on to a high field -near its head the people can make it appear that the discharge is only a -fraction of what it should be. - -On any distributary there are generally some watercourses which have a -poor command, the head at the outlet being, say, ·1 ft. or even less. -Probably the irrigation is a good deal less than it should be. In such -cases the rules may be set aside and a liberal size of outlet given. The -size may be 2 or 3 times the calculated size. There is no harm in this. -The irrigation cannot increase much. Similar cases frequently occur on -inundation canals especially near the heads of canals or distributaries. - -The construction of masonry outlets on a distributary is not usually a -final settlement of the matter. Further adjustments become necessary. -This matter will be dealt with in CHAPTER III. - -On the older canals little or insufficient attention was given to the -question of the sizes of outlets. The sizes were far too great and, as -long as all the outlets in a distributary remained open, water could not -reach the tail. The distributary used to be divided into two or three -reaches and the outlets in the upstream reaches used to be closed -periodically. The closures had to be effected through the agency of -native subordinates and the system gave rise to corruption on a colossal -scale. The tail villages never obtained anything like their proper share -of water. The upper villages were over-watered and the soil was often -water-logged and damaged. Moreover, even if all concerned had the best -intentions, it was impossible to stop all leakage in the closed outlets, -except by making earthen dams in the watercourses, and great waste of -water resulted from this. - -The water level of the distributary with ³⁄₄ full supply, designed so as -to be at least ·5 ft. above the water level in the watercourse heads--or -to be 1 foot above high ground if this simpler plan is adopted--is drawn -on the rough longitudinal section and also the line of F.S., falls being -introduced where desirable and the gradients, F.S. depths of water and -widths of channels being arranged, just as in the case of a canal, so as -to give the required discharges, velocities suited to the soil and a -suitable ratio of depth to velocity. The bed width of a distributary -decreases in whole numbers of feet. The decrease occurs at outlets but -not at every outlet. As the channel becomes smaller its velocity becomes -less and this necessitates, according to the laws of silting and scour, -a reduced depth of water. The height and width of the banks in the tail -portion of a distributary should be made rather greater than -elsewhere--regard being had to the depth and volume of the water--so -that breaches may not occur when the demand abruptly slackens. The -longitudinal section of a distributary should have horizontal lines for -showing the following: - - 1. Datum |5. Draw-off | 9. Bank width |13. Depth of - | | | digging - 2. Bed gradient |6. F.S. discharge|10. Height of |14. Bed level - | | bank | - 3. Village |7. Velocity |11. F.S. depth |15. Ground - | | | level[17] - 4. Land width |8. V₀ |12. Bed width |16. Chainage[18] - -----------------+-----------------+-----------------+---------------- - - [17] Called “Natural Surface” in India. - - [18] Called “Reduced Distance” in India. - -A specimen of a longitudinal section is shown in Fig. 12. It shows only -a few of the above items. In practice all would be shown, large sheets -of paper being used with all the lines and titles printed on them. - -When a distributary is constructed the side slopes are made 1 to 1 in -excavation and 1¹⁄₂ to 1 in embankment. The sides usually silt up till -they are ¹⁄₂ to 1 or even vertical. The silting up to ¹⁄₂ to 1 is, as in -the case of a canal, allowed for in the designing. The berms are left so -that, if any part of the side falls in, the bank will not also fall in. -They also allow of widening of the channel. The remarks made in Art. 6 -regarding the design of banks, apply to distributaries, especially large -ones. - -On a distributary there is seldom much spoil. Where there is no spoil, a -strip of land, outside the bank and 10 feet wide, can be taken up on -either bank from which to obtain earth for repairs. On a minor the width -of the strip is sometimes only 5 feet. - -[Illustration: FIG. 12.] - -When a distributary passes through land which is irrigated from wells, -it frequently cuts through the small watercourses which run from the -well to the fields. In such cases, either a syphon or a supplementary -well is provided at Government cost. If several watercourses, all from -the same well, are cut through, it is generally possible to combine them -for the purpose of the crossing. The wishes of the cultivators in this -matter are met as far as possible. - -The procedure as regards laying out the line on the ground, digging -trial pits, correcting the line and preparing the estimate are the same -as for the case of a canal. - -[Illustration: FIG. 13.] - - -10. =Best System of Distributaries.=--Let AB (Fig. 13) represent a -portion of a distributary, the irrigation boundary CD being two miles -from AB. In order to irrigate a rectangular plot ACDB, the main and -branch watercourses would be arranged somewhat as shown by the full and -dotted lines respectively. Generally, the whole supply of the main -watercourse would be sent in turn down each branch, the other branches -being then dry. The average length open is AGE. The ends of the branches -lie on a line drawn say 200 feet from the lines BD and DC, since it is -not necessary for the watercourses to extend to the outside edges of the -fields. Within the field there are small field watercourses which -extend to every part of it. By describing three rectangles on AC, making -AB greater than, equal to and less than AC, it can be seen that the -average length of watercourse open is least--relatively to the area of -the block--when AB is equal to AC, i.e., when the block served by the -watercourse is square as in the figure. If AB is 4 times AC, the average -length of watercourse open is increased--relatively to the area of the -block--in about the ratio of 3 to 2. Moderate deviations from a square -are of little consequence. - -Suppose two parallel distributaries to be 4 miles apart, each of them -being an average Indian one, say sixteen miles long with a gradient of -one in 4,000, and side slopes of ¹⁄₂ to 1, the bed width and depth of -water at the head being respectively 13·5 feet and 2·9 feet, and at the -tail 3 feet and 1 foot. The discharge of the distributary, with N = -·0225, will be 72 c. ft. per second. The discharge available for the 2 -mile strip along one bank will be 36 c. ft. per second. If the duty is -300 acres per c. ft. the area irrigated in this strip will be 10,800 -acres, or 1,350 acres for each of the eight squares like ACDB. Each main -watercourse would then have to discharge 4·5 c. ft. per second. -Supposing its gradient to be 1 in 4,000 and its side slopes ¹⁄₂ to 1 and -N to be ·0225, its bed width would be 3 feet and depth of water 1·45 -feet. Its wet border would be 6·3 feet, and its average length 5280√2 + -5280 - 200 or 12,546 feet. Its wetted area would be 79,040 square feet, -and the total wetted area of the 16 watercourses--on the two sides of -the distributary--would be 1,264,640 square feet. The wetted border of -the distributary itself is 19·5 feet at the head and 5 feet at the tail, -average 12·25 feet, and its wetted area is 5,280 × 16 × 12·25 or -1,034,880 square feet. - -If the distributaries were two miles apart, there would be twice the -number of distributaries, and each square would be one square mile -instead of four. Each watercourse would have to discharge 1·125 c. ft. -per second. It would have a bed width of 2 ft., depth of water ·8 ft., -wet border 3·8 feet, length 6,173 feet, and wetted area 23,457 feet. The -total wetted area of the 64 water courses would be 1,501,248 square -feet, or 18 per cent. more than before. Each distributary would -discharge 36 c. ft. per second, the bed width and depth at the head -being 10 feet and 2·24 feet, and at the tail 2 feet and ·75 feet. The -wet border at the head and tail would be 14·5 and 3·5 feet, mean 9 feet, -and the wetted area of the two distributaries would be 1,520,640 square -feet or 50 per cent. more than before. Supposing that, in the case of -the larger distributary considered above, the 2-mile square was -considered too large, and that rectangles 1 mile wide were adopted, so -that the watercourses were a mile apart, their number would be doubled -and their length and size reduced. Their total wetted area would not be -greatly affected, but the difference in the wetted areas of the two -small distributaries as compared with the one large one, would be the -same as before. In practice, of course, distributaries are not always -parallel, nor are the blocks of irrigation all squares, and frequently, -owing to peculiarities in the levels of the ground or the features of -the country, or the boundaries of villages, it is necessary to align the -watercourses in a particular manner, or to construct more than one -watercourse where one would otherwise have sufficed, but the above -calculations show in a general way the advantages of large watercourses -and of not placing the distributaries too near together. - -It is commonly said that a watercourse discharging more than 4 or 5 c. -ft. per second is objectionable because the cultivators, if there are -too many of them on one watercourse, cannot organize themselves in order -to work it and keep it in order. This matter is much exaggerated. On the -inundation canals of the Punjab a watercourse often discharges 10 c. ft. -per second, and is several miles long and requires heavy clearances, but -the people have no particular difficulty in managing it. Kennedy, a -great authority on questions of irrigation, states that the length of a -watercourse may be three miles. This, if the angle made by a watercourse -with the distributary is 45°, gives rather more than two miles as the -width of the strip to be irrigated. - -Suppose that a distributary instead of being two miles from each side of -the irrigated strip, ran along one side of it, and was four miles from -the other side. If the block were square, as before, the side of a -square would be 4 miles, and each watercourse would have to discharge 18 -c. ft. per second, which is far too much. The blocks would have to be -rectangles, each being only one mile wide measured parallel to the -distributary. It has been already seen that the length of watercourse in -this case is greater than when the block is square and each side is two -miles. Thus centrality in the alignment of the distributary is an -advantage. - -A minor distributary has been defined (CHAPTER II., Art. 3) as being one -discharging not more than 40 c. ft. per second, but the term has come to -be used to designate a branch of a major distributary, and in that sense -it will be used in this article. When the shape of the area commanded by -a distributary is such that watercourses exceeding 2 miles in length -would otherwise be required, one or more minors are often added. -Frequently it is a question whether to let some of the watercourses be -more than two miles long, or to construct a minor and thus shorten the -watercourses to perhaps only one mile. Which method is best has not been -definitely settled. It is known that the loss of water in watercourses -is heavy, but if a minor is added the loss in it has to be considered. -The loss must be high in any channel in which the ratio of wet border to -sectional area is small. The minor also costs money in construction and -in maintenance. On the whole the matter, as far as concerns cost and -loss of water, is, perhaps, almost evenly balanced, but as regards -distribution of the supply a system without minors is preferable. The -off-take of a minor is generally far from the canal, i.e., in a more or -less out-of-the-way place, and it is impossible to see that the -regulation is properly carried out. Irregularities and corruption are -sure to arise. Even if the supply is fairly distributed as between the -minor and the distributary it is almost certain that the regulator, if a -double one, will be manipulated for the illegal benefit of outlets in -the distributary upstream of the bifurcation. There are sure to be some -such outlets not very far distant. In any case each minor adds one, if -not two, to the already very large number of gauges which have to be -entered daily in the sub-divisional officer’s register (CHAPTER III., -Art. 3), and adds also to the mileage of channel to be inspected and -maintained. These considerations should, in many cases, though of course -not in all, turn the scale against the construction of a minor. At one -time it became usual to construct minors even when watercourses more -than two miles long would not otherwise have resulted. This custom was -condemned some years ago, and is not likely to be re-established. Most -of the difficulties just mentioned can, in the case of a minor which is -not too large, either absolutely or relatively to the main distributary -downstream of the off-take, be got over by making the minor head like a -watercourse outlet, building it up to the proper size, removing the -regulating apparatus and abolishing the reading of the gauge, but in -this case the minor is not likely to be bigger than a large watercourse. -Such minors should not be constructed, and any existing ones should, -after the head has been treated as above, be made over to the people and -considered as watercourses. - - -11. =Outlets.=--The top of the head and tail walls of an outlet are -level with the F.S. levels in the distributary and watercourse -respectively. The steps in the head wall enable the cultivators to go -down either to stop up the outlet or to remove any obstruction. The -stepping is arranged so as to fall inside the side slope ultimately -proposed. It is usual, in some places, to have the entrance to the -“barrel” of the outlet made of cast iron. The cast iron pieces are made -of various standard sizes. This to some extent prevents the “barrel” -being built to a wrong size. A discrepancy between the size of the -masonry barrel and that of the iron would be noticed, but if the masonry -barrel is built too large the iron head does not always restrict the -discharge. The action is the same as in a “diverging tube” well known in -hydraulics. - -For sizes up to about 50 or 60 square inches the barrel should be nearly -square. For larger sizes the height should exceed the width. Up to -about 100 or 120 square inches the width can be kept down to 7 or 8 -inches so that an ordinary brick can be laid across to form the roof. -For larger outlets the height can be from 1·5 to 3 times the width, and -the roof can be made of large bricks, concrete blocks or slabs of stone -or of a flat arch of brickwork or by corbelling, but in this last case -there should be two complete courses above the top of the outlet. The -less the width the cheaper the roof, the easier the adjustment of size -and the less the tendency to silt deposit during low supplies. If pipes -are used they should be laid in concrete. If cast iron head pieces are -to be used there should be several sizes of one width and the widths of -the masonry outlets should be made to suit these widths. - -A masonry outlet is not generally built till the watercourse has been -sometime in use. The exact position of the outlet should then be so -fixed that the watercourse shall run out straight or with a curve and -should not be crooked. - -The width between parapets should be, for a driving road or one to be -made into such, 10 ft. (if the bank is wider, it should be narrowed just -at the outlet site) and for a non-driving road, 8 feet to 3 feet -according to the ultimate width of the bank. Earth backing should be -most carefully put in and rammed, otherwise a breach may occur and the -outlet be destroyed. - -Various attempts have been made to provide gates or shutters for -outlets. The chief result has been trouble and increased cost. If -grooves are made and shutters provided, the shutters are soon broken or -lost by the people. Hinged flap shutters are objectionable because they -are often closed by boys or by malicious persons or by neighbours who -wish to increase the supply in their own outlet. The cultivator, when he -wishes to reduce the supply or to close the outlet, can easily do this -by obstructing the orifice with a piece of wood or an earthenware vessel -or a bundle of brushwood or grass. - -As regards temporary outlets, wooden outlets if large (unless made of -seasoned wood and therefore costly) are liable to give great trouble. -Water escapes round the outside or through the joints. Pipes may do well -if laid in puddle but are brittle and costly if of large size. The -irrigators may interfere both with wooden outlets and pipes and they are -liable to be displaced or broken. A temporary outlet, if small, can be -made of bricks laid in mud. The joints can be pointed with lime mortar. -When the outlet is made permanent the same bricks are used again. But -all kinds of temporary outlets are liable to give trouble especially in -light or sandy soil. There is much to be said in favour of building -masonry outlets at the first, making a barrel only, _i.e._, omitting the -head and tail walls and taking the chance of having to alter the size. -The alteration is not very expensive. The head and tail walls are built -when the size has been finally settled. The adjustment can be made by -raising or lowering the roof. This should be done over the whole length -of the outlet but lowering can be done temporarily over a length of 3 -feet at the tail end of the outlet. This can be done even when the -distributary is in flow. A reduction over a short length at the upstream -end of a barrel does not, as already remarked, necessarily reduce the -discharge much. - -On inundation canals the rules regarding outlets have to be modified. -Great numbers of watercourses take off directly from the canals. In such -cases, especially near the head of a canal, the ground to be watered is -often 5 to 8 feet above the canal bed and it is wholly unsuitable to -place the outlet at bed level. The cost of the tail wall would be -excessive. The floor level in such cases must be at about the lowest -probable cleared bed level of the watercourse, say, in order to be safe, -a foot or half a foot below the usual cleared bed of the watercourse, so -that water need never be prevented from entering the watercourse. The -irrigators should be consulted as to the floor level and their wishes be -attended to as far as possible. For lift outlets the floor should be at -the bed level of the canal or distributary. If this bed is to be raised -in the course of remodelling, the floor should be at the old bed level -until the bed has actually been raised, unless there is a weir which -raises the water. It is necessary that lift outlets should work however -small the canal supply may be. In a distributary or small canal, the -head wall should be built up to F.S. level but in a canal with deep -water the head wall should reach up to just above the roof of the outlet -and be submerged in high supplies. The stepping of the head wall should -be set back if the channel is to be widened and should project into the -channel if the channel is to be narrowed. The centre line of the channel -near the outlet site must always be laid down and the outlet built at -right angles to it and also at the correct distance from it. - -Occasionally there is a wide berm, say 20 ft. or even 50 ft., between a -channel and its bank. In such a case the outlet should be built to suit -the bank. The long open cut is however objectionable because the people -clear it and heap the spoil in Government land. Sometimes the bank, -especially if it is crooked, can be shifted so as to come close to the -channel at the outlet site. Sometimes the outlets on inundation canals -are large. For outlets of more than 2·5 square feet in area, grooves -should be provided so that the cultivators can use a gate if necessary. - - -12. =Masonry Works.=--The positions and descriptions of all the masonry -works of a proposed canal or distributary are of course shown on the -longitudinal section of the channel and from this the discharges and -water levels are obtained. The principles of design to be followed[19] -for bridges, weirs, falls, regulators and syphons, are discussed in -_River and Canal Engineering_. It is mentioned that there is no special -reason for making the waterway of a regulator exactly the same as that -of the stream, and that the waterway may be such as to give the maximum -velocity considered desirable, and that the foundations of a bridge -should be made so deep that it will be possible to add a floor, at a -lower level than the bed of the stream--with the upstream and downstream -pitching sloping up to the bed--so as to increase the waterway and so -save pulling down the bridge in case the discharge of the channel is -increased. It remains to consider certain points affecting Irrigation -Canals. - - [19] So far as concerns their capacity for dealing with flowing water. - -The span of a bridge, where there are no piers, is generally made as -shown by the dotted lines in Figure 14, so that the mean width of -waterway is the same as that of the channel. The arches, in Northern -India, used at one time to be 60° as shown by the upper curved line, but -in recent years arches of 90° as shown by the lower curved line, have -frequently been adopted, the springing of the arch being below the F.S. -level, so that the stream is somewhat contracted. The 90° arch gives a -reduced thickness and height of abutment. It causes increased -disturbance of the water, and this may necessitate more downstream -protection. An advantage of having the springing not lower than the F.S. -level is that this admits of a raising of the F.S. level in case the -channel is remodelled, and this arrangement is still common on -distributaries. - -[Illustration: FIG. 14.] - -When a fall and bridge are combined, the bridge is placed below the fall -as this gives a lower level for the roadway. The side walls of the fall -are produced downstream to form those of the bridge. - -The roads in India are generally unfenced and the banks of canals close -to bridges, on both sides of the canal and both above and below the -bridge, are generally more or less worn down by cattle, which, when -being driven home in the evening and out to graze in the morning, go -down to the stream to drink. In order to prevent this damage the banks -are sometimes pitched, above the bridge as well as below it, but the -cattle generally make a fresh “ghát” further away. The best plan is to -allow a “ghát” on one bank either above or below the bridge and to -protect the other three places. - -In the Punjab the widths of roadways between the kerbs and parapets of -bridges respectively have been fixed as follows:-- - - --------------+----------------+------------------- - KIND OF ROAD.| NEAR TOWNS.[20]|IN THE COUNTRY.[21] - --------------+------+---------+--------+---------- - |Kerbs.|Parapets.| Kerbs. | Parapets. - --------------+------+---------+--------+---------- - Provincial | 22 | 23·5 | 16 | 17·5 - District | 18 | 19·5 | 14 | 15·5 - Village | 14 | 15·5 | 8·5 | 10 - --------------+------+---------+--------+---------- - - [20] The figures show the maximum. The general width should be the - same as for neighbouring bridges on the same road. - - [21] The parapets should be whitewashed so as to be visible at night. - -[Illustration: FIG. 15.] - -Fig. 15 shows a head regulator for a distributary. The scale is 10 feet -to an inch. It has a double set of grooves for the insertion of the -planks with which the regulation is effected. Only one set of grooves is -ordinarily used, but when the distributary has to be closed for silt -clearance and all leakage stopped, both sets of grooves can be used and -earth rammed in between the two sets of planks. The floor is shown a -foot lower than the bed of the distributary. This reduces the action of -the water on the floor, and enables the bed of the distributary to be -lowered if ever the occasion for this should arise. This is a good -rule--in spite of the fact that in re-modellings the tendency is for the -beds to be raised--for all regulators or bridges, a raised sill being -added (in regulators) to reduce the length of the needles or the number -of the planks. Such sill should, where needles are to be used, be fairly -wide, especially if regulation is to be done while the masonry is -somewhat new. The distributary shown has a bed width of 10 ft. The span -of the two openings in the head might have been four feet each, but are -actually five feet, and this enables the distributary to be increased in -size at any time. The pitched portion of the channel tapers. Unless -needles are used, instead of horizontal planks, spans are not usually -greater than 5 or 6 feet. Longer spans would give rise to difficulties -in manipulating the planks. Sometimes distributary heads are built skew, -but there is seldom or never any good reason for this. A curve can -always be introduced below the head to give the alignment the desired -direction.[22] The small circles shown on the plan are “bumping posts.” -On the left is shown a portion of the small raised bank at the edge of -the road. - - [22] The curve can be quite sharp (see CHAP. I., Art. 2), and can be - made, if necessary, within the length of the pitching. - -[Illustration: FIG. 16.] - -Figure 16 is a double regulator with needles. The scale is 30 feet to an -inch. The spans are 15 feet. The roadway is on arches, but the -regulating platform on steel beams. The needles are seen at the upstream -sides of the regulators. They are worked from the platforms to which -access is obtained through the gaps in the upstream parapets. The -regulating platform should generally be only just clear of the F.S. -level, and therefore lower than the roadway. - -[Illustration: NEEDLE REGULATOR AND BRIDGE. - -Needles lying on Bank. - -_To face p. 85._] - -Frequently the roadway of a bridge or small regulator is carried, not on -arches, but on steel beams. The railings may be of wood or of gas pipe -with the ends plugged, running through angle iron posts. In the case -of such a regulator the roadway is sometimes so light that camels are -not allowed to cross over. This causes unnecessary hardship. Bridges are -not too numerous. If the regulation is done by gates, both road and -platform are carried on arches. - -The regulators on inundation canals, and some on perennial canals, are -not strong enough to admit of the flow of water being entirely stopped, -so that the depth of water would be perhaps 10 feet upstream and nil -downstream. This might cause the overturning of the piers, or the -formation of streams under the floor. In such cases a maximum -permissible heading up is decided on. Such orders are, in India, liable -to be lost sight of in course of time, and they are, at least on -inundation canals, where sudden emergencies often occur, hardly -reasonable. An engine driver is not told that he must never entirely -close his throttle valve. Regulators should be so designed that the -water can be completely shut off. - -The following remarks show the chief points in favour of needles and -horizontal planks respectively. - - _Advantages of Needles._ Needles can be placed or removed by one man. - - Needles do not require hooks, etc., which are liable to be broken or - lost. - - A needle regulator requires few piers, and is therefore cheap. - - Water falling over planks throws a strain on the floor. - - Regulation with needles is easy and rapid. A jammed plank, especially - if low down and not horizontal, may give great trouble. - - _Advantages of Planks._ Floating rubbish is not liable to collect - above the Regulator because the water flows over the planks. - - By means of double grooves and earth filling, leakage can be quite - stopped. - -For large works the advantages are generally with needles, but for small -works, _e.g._ distributary heads and shallow water, with planks. Needles -14 feet long are not too long for trained men. Planks are more likely -than needles to arrest rolling sand, and this can be taken into -consideration in designing double regulators. See number 8 of Kennedy’s -rules, Article 5. When planks are used there should be two sets of -grooves. Planks are very suitable for escape heads which have only -occasionally to be opened, earth being filled in between the two sets of -planks. - -[Illustration: FIG. 16A] - -Regarding notched falls, in the case of small distributaries the notches -are so narrow that they are extremely liable to be obstructed either -accidentally by floating rubbish or wilfully by persons whose outlets -are upstream of them. Weirs are not open to this objection, and are -frequently adopted. There is not the least chance of their causing any -silting worth mentioning. A simple weir if made of the proper height for -the F.S. discharge, will cause a slight heading up with ³⁄₄ths of the -F.S. discharge, and this unfairly benefits any outlets for a -considerable distance upstream of the weir. This difficulty can be got -over by making the weir as in Fig. 16A. - -[Illustration: BRIDGE AND NOTCH FALL. - -In this case the usual practice of placing the bridge downstream of the -fall has not been followed. - -The gauge well is seen on the left bank. - -_To face p. 87._] - -For cisterns below falls the usual rule for the depth is - - K = H + ∛H √D - -where H is the depth of water in the upstream reach, and D is the -difference between the upstream and downstream water levels. Another -rule for distributaries is - - H + D - K = ----- - 3 - -the length of the cistern being 3 H and its width the bed width of the -channel. - -At “incomplete” falls, i.e., where the tail water level is above the -crest, it is not unusual to construct a low-level arch, which forms a -syphon. The object is to allay the surging of the surface water. - -The question of skew bridges has been dealt with in Art. 3. Another -question is that of the heights of bridges. Irrigation channels, -especially the smaller ones, are very frequently at a high level, and -bridges have ramps which are expensive to make and to maintain, and are -inconvenient. The lowering of distributary bridges in such cases, so -that they become syphons, or nearly so, has often been advocated and is -frequently desirable. The bed should slope down to the floor and up -again. The heading up can be reduced by giving ample waterway, but it -will not be necessary to do this if there is head to spare. The fall in -the water surface can be recognised and shown on the longitudinal -section. The structure becomes one of the incomplete falls above -described. The crown of the arch can, if desirable, be kept above F.S. -level, so that floating rubbish will not accumulate. - -The width between the parapets of a regulator can be 10 feet in the case -of a driving road. It may be less, according to the width of the bank, -in other cases. - -The upper layer of the floor of a bridge or regulator is of brick on -edge. Below this there is a layer of brick laid flat, and below this, -concrete of a thickness ranging from ·5 feet to 3 feet. The thicknesses -of piers range from 1·5 to 3 feet. - -The bricks used for canal work in Northern India are 10 inches long, -4⁷⁄₈ inches wide, and 2³⁄₄ inches thick. The thicknesses of walls are -about ·83, 1·25, 1·7, 2·1, 2·5 feet, and so on. - -The slopes of ramps should be about 3 in 100 for district roads, and 5 -in 100 for village roads. - -Railings should be provided along the tops of high walls and top of -pitching near to public roads or canal patrol roads. Bumping posts -should be provided for all parapets, and should not be so placed as to -seriously obstruct the roadway. - -The quarters for the regulating staff should, when convenient, be in the -fork between the two principal branches. They may be on the bank--with -foundations on pillars carried down to ground level--but not in such a -position as to obstruct the road or any road likely to be made. Rests -consisting of two parallel timbers bolted to blocks of masonry reaching -up a foot from the ground, should be provided for the needles or planks. -The bolt head should be countersunk so as not to damage the needles and -planks when they are hurriedly laid down. - -When two or more works are close together they should be made to -conform, and the whole site should be considered with reference to a -neat and suitable arrangement of works, ramps and roadways. If an outlet -is near to a minor or distributary head the parapets of the two should -be in line. If two masonry works of any kind are near together it is -often suitable to pitch the intervening space. If there are outlets or -distributaries on opposite banks they should be exactly opposite each -other. Where a road crosses a bridge or regulator, the bank should be at -the same level as the road, the bank being gradually ramped back to its -original level. The space in front of any quarters should have a slight -slope for drainage, but otherwise be at one level and be connected with -the road or bank by proper ramps. The berm or bank should be made at the -exact level of the top of any pitching or side wall which adjoins it. -Wing walls are frequently made too short, so that the earth at their -ends forms a steep slope and is worn away, and the bank or roadway is -cut into. The walls should extend to such a point that the earth at -their ends cannot assume a slope steeper than the slope of the bank. - -It is obvious that for every masonry work there should be a large scale -site plan[23] showing all roads, ramps, and adjoining works, both -existing and proposed roads being shown for some little distance from -the work. - - [23] It is, or was until recently, in some parts of India, the custom - to omit the preparation of site plans, and to leave the fixing of the - exact site of a work and the arrangement of ramps and other details to - the judgment of the assistant engineer who was building it. Much - unsightly work resulted. A chief engineer in the Punjab recently - issued some orders on the subject. - -For each kind of masonry work there is usually a type design. A few of -its dimensions, which are fixed, are marked on it. The other dimensions -are variable. It would be a great advantage to add to the design a -tabular statement to show how these dimensions should vary under -different circumstances. - -[Illustration: FIG. 17.] - -[Illustration: FIG. 18.] - - -13. =Pitching.= The object of pitching upstream of bridges or regulators -or downstream of bridges where there may be little or no scouring -action, may be partly to protect the bank from damage by cattle or wear, -or to prevent sandy sides from falling in. In such cases there may be -pitching of the sides only, and it may be of brick on edge laid dry and -under this one brick flat resting on rammed ballast (Fig. 17). -Downstream of regulators or weirs and downstream of bridges if -contracted or having piers which cause a rush of water, especially if -the soil is soft, the side pitching may be as above, but with the bricks -over one-sixth of the area placed on end and projecting for half their -length. This “roughened pitching” tends somewhat to reduce the eddying. -The bed protection should be solid concrete or blocks of concrete or -masonry. Immediately downstream of regulators or weirs where there is -great disturbance, both side and bed pitching may consist of solid -concrete or of concrete or masonry blocks (Fig. 18). - -[Illustration: FIG. 19.] - -Three kinds of toe walls are shown in Figures 17, 19 and 20. The kind -shown in Fig. 19 contains, for a given depth below the bed, far more -masonry than the one shown in Fig. 17. It is also liable to be displaced -and broken if scour occurs. - -[Illustration: FIG. 20.] - -The earth should in all cases be carefully cut to the proper slope, so -that no made earth has to be added. If the slope has already fallen in -too much, well rammed earth should be added. The flat brick and rammed -ballast can be varied as the work proceeds, more being used in soft -places and less in hard. - -In some parts of the Punjab, large bricks, the length, breadth, and -thickness being about twice the corresponding dimensions of an ordinary -brick, are made, and are extremely useful and cheap for pitching. Where -the soil is sandy such bricks can be burned without cracking. - -Sometimes the curtain wall which runs across the bed at the downstream -end of the pitching is carried into the banks and built up so as to form -a profile wall (Fig. 21). This is not very suitable, because the -pitching of the sides is apt to settle and leave the profile wall -standing out. It is better to lay a row of blocks on the slope. If a -hole tends to form in the bed downstream of the curtain wall, blocks of -masonry or concrete can be laid and left to take up their own positions -(Fig. 22). - -[Illustration: FIG. 21.] - -[Illustration: FIG. 22.] - -When scour of the bed or sides occurs downstream of pitching, it is -sometimes said that any extension of the pitching downstream is followed -by extension of the scour. This may happen if the cross section of the -stream downstream of the pitched section has become greater than the -pitched section. In this case there is eddying, due to abrupt -enlargement of the stream where the pitching ends. The increased width -and lowered bed level (not counting mere local hollows) of the stream -should be adhered to in the pitching. Where the masonry of the regulator -ends and the pitching begins, there will be an abrupt or tapered -enlargement, but the eddies--at very low supplies there may be a -fall--cannot do harm. - -This principle of enlarging the pitched cross section can be followed, -even in a new channel, if the soil is light and scour is feared, and for -this reason the matter is mentioned in the present Chapter instead of -in Chapter III. It was once the custom to splay out the sides of a -channel, downstream of a regulator or weir, so as to form a sort of pool -in which the eddies exhausted themselves, but this gives curved banks -and requires extra land and is not a very convenient or neat -arrangement. Where scour of the sides is likely to occur, or has -occurred, immediately downstream of the pitching the latter may be -turned in as shown in Fig. 23. - -[Illustration: FIG. 23.] - -Pitching has constantly to be replaced or extended owing, generally, to -failure to pitch a sufficient length or to ram well the earth under the -pitching, or to use properly rammed ballast or flat brick, or to give -proper bed protection, or to the use of dry brick pitching when a -stronger kind is needed. - -The side slopes of pitching should be 1 to 1. They can be ¹⁄₂ to 1 in -rare cases, _e.g._, when there is no room for 1 to 1, or in continuation -of existing ¹⁄₂ to 1 pitching. No absolute rule can be laid down as to -the length to be pitched, but in a Punjab distributary it is often about -5 times the bed width. - - -14. =Miscellaneous Items.= On Indian canals the chainage[24] is marked -at every thousand feet. Five thousand feet is called a “canal mile.” -The distance marks are often cast iron slabs, fixed in a cylindrical -block of brickwork about 2·1 feet in diameter and 1·5 feet high, the -upper edge being rounded to a radius of ·4 feet. The wedge-shaped bricks -for these blocks are specially moulded. The iron slab should project -about eight inches and have about a foot embedded in the brickwork. - - [24] In India, instead of the simple word “chainage” the term “reduced - distance” is used. It is the distance reduced to a common starting - point as levels are reduced to mean sea level. The expression is - puzzling to non-professionals and new comers. - -On a canal having a wide bank the distance mark is put at the outer edge -of the patrol bank, earth being added, if necessary, to increase the -width. On a distributary with a narrow bank the mark should be on the -opposite bank not the patrol bank. To enable the miles to be easily -distinguished the masonry block can be sunk only ·5 foot in the ground, -the others being sunk a foot. In all cases the masonry block rests on a -pillar, 1·7 feet square, of bricks laid in mud, carried down to the -ground level. - -Profile walls (Fig. 21, page 92) used occasionally to be built at -frequent intervals along a distributary. They will not prevent scour -occurring, if the stream is tending to scour, unless very close -together. Such walls are of some use as showing whether the channel is -altering, but they are expensive and have to be altered if, as often -happens, the channel is remodelled. It is a much better plan to lay down -blocks--about 1¹⁄₄ foot cubes--of masonry or concrete, along the centre -line at every 500 feet, with their upper faces level with the bed. If -the bed scours they may be displaced but otherwise they are useful not -only for showing what silt, if any, has deposited, but for showing the -centre line of the channel. Without them the centre line is liable to be -altered in silt clearances or berm cuttings. To enable a block to be -readily found and to be replaced in proper position if displaced, there -should be two small concrete pillars exactly opposite to it and -equidistant from it, one on either bank of the channel. Such blocks and -pillars may with advantage be placed at quite short intervals on curves. - -The rest houses for the use of officials on tour are generally at -intervals of about 8 to 14 miles. There is generally a rest house near -to a large regulator and frequently there is one near to a small -regulator. This facilitates inspection work and discharge observations -and it saves money, because the house can be looked after by one of the -regulating staff. Not infrequently the house is placed just too far away -from the regulator. Similarly if a rest house is near a railway station -it should be within a quarter of a mile of it--always provided that this -does not bring it too near to villages or huts--and not a mile or more -away as is sometimes the case. It is also a mistake to place a rest -house off the line of channel unless perhaps when it is on a district -road which crosses the channel. - - - - -CHAPTER III. - -THE WORKING OF A CANAL. - - -1. =Preliminary Remarks.= A large canal is under a Superintending -Engineer and it often constitutes his sole charge. It consists generally -of three to five “divisions,” each under an Executive Engineer. A -division has two to four subdivisions, each under a Subdivisional -Officer. A subdivision is divided, for purpose of engineering work and -maintenance, into several, generally three or four, sections, each -consisting of some 20 miles of canal and some 40 miles of distributary, -and being in charge of a native overseer or suboverseer, and for -purposes of water distribution and revenue, into a few sections each -having, perhaps, some 30,000 acres of irrigation and being in charge of -a native zilladar. As far as possible the boundaries of divisions and -subdivisions are co-terminous with those of the branches of the canal. A -distributary is always wholly within a subdivision. At every regulator -there is a gauge reader, who, supplied when necessary with permanent -assistants, sees to the regulation of the supply. If there is a -telegraph office at the regulator the telegraph “signaller” may have -charge of the regulation. The zilladar has a staff of some ten or twelve -patwaris, who record in books the fields watered and who are in touch -with the people and know when the demand for water is great, moderate or -small, and for what kind of crops it is needed. In each division there -is generally a Deputy Collector who is a native official, ranking as a -Subdivisional Officer. His duty is to specially supervise the revenue -staff in the whole division. Both he and the Subdivisional Officer have -magisterial powers which are exercised in trying petty cases connected -with the canal. - -Along a main canal and its branches there is nearly always a “canal dak” -or system of conveyance of bags containing correspondence for the -officials stationed on the canal or touring along it. Along the main -line, and most of the way down the branches, there is a line of -telegraph for the special use of the canal officials. The telegraph -offices are at the chief regulators, with tapping stations, for the use -of officials on tour, at the rest houses near to which the line runs. - -However carefully a canal has been designed, alterations in the channels -from silting and scour soon take place and they go on more or less -without cessation. In a distributary, especially if the gradient has of -necessity been made somewhat flat, there is quite likely to be a deposit -in the upper reach. The deposit is generally greatest at the head and -decreases, in going downstream, at a fairly uniform rate. It may extend -for half-a-mile or less or more. Or a deposit may occur on the sides, -which grow out and contract the channel. This often occurs over a great -length of a distributary or even over the whole of it. Sometimes a -distributary scours its bed, or the sides may fall in somewhat. -Clearances of the silt and cutting of the berms are effected at -intervals. Falling in of the sides may be stopped by means of bushing, -and scour of the bed may be stopped by raising the crest of a fall or by -introducing a weir, but in the meantime the changes cause the discharge -tables for the distributary to become more or less erroneous. In many -cases silt deposits in the upper part of the distributary during the -summer months when the river water is heavily silted and scours away -again in the winter, the régime of the channel being, on the whole, -permanent. The changes which occur in the branches and main canal are -similar to the above and the remedies adopted are similar. On some of -the older canals the scour was so serious that many intermediate weirs -had to be constructed. The remarkable silting in the head reach of the -Sirhind Canal has been described in _River and Canal Engineering_, -Chapter V. The remedy consisted in keeping the gates of the -under-sluices properly closed so that a pond was formed in which the -river silt deposited. When necessary the canal is closed, the sluices -opened, and the silt scoured away. For a plan of the headworks see fig. -24. - -In working a canal, it is necessary to arrange so that the water sent -down any channel is as nearly as possible in accordance with the demand. -The zilladar supplies the Subdivisional Officer, every week or ten days, -with an “indent” showing how much water is required in each distributary -and the Subdivisional Officer makes indents on the subdivision next -above. The officer in charge of the headworks thus knows what the demand -is. When it is more than the supply available, the water is dealt out to -the various divisions according to rules approved of by the -Superintending Engineer of the canal. - -[Illustration: FIG. 24.] - -Every gauge-reader has to be given definite instructions as to the gauge -reading to be maintained, until further orders, in each distributary. At -the places where the large branches take off, the gauge reader is -instructed what gauge to maintain in each. In the event of too much -water arriving, he turns the surplus into the escape if there is one. If -there is no escape he has usually to raise the gauge readings of the -branches by equal amounts. By means of the telegraph, adjustment is -promptly effected at the headworks. - -It has already been mentioned that rain may cause an abrupt reduction -in, or even cessation of the demand for water. At the same time it -increases the actual supply. Rain, or the signs of rain, in any part of -a canal system ought always to be reported to the other parts. Owing to -changes in the channels, to fluctuation in the water level of the river, -especially during the night, to rain or to changes in the temperature -and moisture of the air and to lack of continuous attention on the part -of the gauge reader, particularly at night, there is a constant, though -perhaps small, fluctuation in the water level in all parts of a canal. - -It may happen that--owing to enlargement of the channels by scour, or to -other causes--the channels of a canal system are able to carry more -water than was intended. In such cases the channels are usually run with -as much as they can carry. This may give a lavish supply and a lowered -duty, but it increases the irrigated area. To restrict the supply would -cause loss of revenue. Sometimes however, it is restricted to prevent -water-logging of the soil. The proper procedure is to extend the canal -to other tracts. - -In India the farmers pay for the water, not according to the volume -used, but according to the area irrigated. Different rates per acre are -charged for different kinds of crops according to the varying amounts -of water which they are known to require. Sugarcane, which is sown in -the spring and stands for nearly a year before being cut, thus extending -over the whole of the kharif and most of the rabi, is assessed at the -highest rate. Next comes rice which crop, though only four or five -months elapse between its sowing and reaping, requires a great quantity -of water. Gardens which receive water all the year round also pay a high -rate. Other kharif crops are cotton and millet. The chief rabi crops are -wheat, barley and “gram.” - -Every field irrigated is booked by a patwari who is provided with a -“field map” and “field book” for each village (perhaps 6 or 8) in his -beat. The map enables him to recognise at a glance the field in which he -is standing. It has a number in the map and, by referring to this number -in the field book, he finds the area of the field. The patwari is also -provided with a “field register” in which he books each field which is -watered, showing its area and the kind of crop grown, the date of -booking and the name of the owner and tenant. He goes about entering up -all new irrigation and his proceedings are subjected to rigorous check -by the zilladar and Deputy Collector, and also by the engineering staff. -At the end of the crop the entries are abstracted into a “demand -statement” in which all the fields cultivated by one person are brought -together and, the proper rates being applied to them, the sum payable by -this person is arrived at. The demand statement goes to the Collector of -the district, who levies the money and pays it into the Treasury to the -credit of the canal concerned. There is a special charge for any land -watered in an “unauthorised manner.” This includes taking water when it -was another man’s turn, or taking it from an outlet which has been -wilfully enlarged or--in some districts--from another man’s outlet even -with his consent. The sizes of the outlets are carefully apportioned to -the land allotted to them and the area which they irrigate is constantly -being looked into in order to see if the size is correct or needs -altering. If a man borrows water from another outlet such borrowing may -or may not come to light but in any case confusion as to outlet sizes -results. - -The water rates charged for ordinary authorised irrigation are decidedly -low. In one district there was a case in which a man, being unable to -get as much water as he needed from his own outlet, took water for some -fields, by permission, from a neighbour’s outlet. This being found out -he was charged for those fields at double the usual rate. He continued -regularly to use the water and to pay the double rate. There were -several cases of this kind in that one district. - -Since payment for the water is not made according to the volume used, -the cultivators are more or less careless and wasteful in using it. As a -rule they over-water the land and frequently damage or spoil it by -water-logging. They do not always keep in proper order the banks of the -watercourses. The banks often breach and water escapes. Any area thus -flooded is charged for if it is seen by an official. The engineers have -power to close such a watercourse until it is put in order, but this -would cause loss of revenue and is not often done. The real remedy for -all this is, as already stated, rigid restriction of the supply. The -people will then learn--they are already learning--to use water more -economically. - -When the crop in any field or part of a field fails to come to maturity, -the water rate on it is remitted. The failed area is known, in the -Punjab, as “kharába.” On some canals the failed areas are liable to be -large and an irrigation register, in order to be complete, has to show -them or, what is the same thing, to show both the gross and the net -areas, the latter being the area left after deducting the kharába or -remitted area. - - -2. =Gauges and Regulation.=--In every canal, branch and major or minor -distributary there is a “head gauge” below the head regulator. At every -double regulator there is a gauge in each branch and also an upstream -gauge. These gauges are used for the regulation of the supply. The zeros -of the gauges are at the bed levels. Tables are prepared showing the -discharges corresponding to each gauge reading--except in the case of -upstream gauges--at intervals of ·1 foot. - -The question often arises whether it is necessary to have a gauge near -the tail of a distributary. If the outlets have not been properly -adjusted and if water does not reach the tail in proper quantity, a tail -gauge is absolutely essential and its readings should be carefully -watched by the Sub-divisional Officer. To take no action until -complaints arise or until the irrigation returns at the end of the crop -show that some one has suffered, is not correct. When it is known that -sufficient water always reaches the tail, a tail gauge is not necessary. - -There may be intermediate gauges on a canal or branch or distributary. -For convenience of reading they are usually at places where a -distributary or minor takes off or where there is a rest house. They -serve to show whether the water level at that place alters while that -at other places is stationary, and thus give indications of any changes -occurring in the channel. The number of such intermediate gauges should -be rigorously kept down. In fact hardly any are necessary. The gauge -register which the Subdivisional Officer has to inspect daily, is, in -any case, voluminous enough. - -At a double regulator it is never necessary, except as a very temporary -arrangement in case of an accident, to partially close both channels at -once. One or the other should be fully open. The upstream gauge reading -shows whether this rule is being adhered to. If the bed levels of all -three channels at the regulator are the same, the reading on one or -other of the downstream gauges should be about the same--for the fall in -the water passing through an open regulator is generally negligible--as -that of the upstream gauge. In other cases the difference in the bed -levels has to be taken into account. - -Immediately downstream of the off-take of a channel, there is, unless -the water flows in without any appreciable fall, much oscillation of the -water. For this reason the gauge is frequently fixed some 500 feet down -the channel. This is anything but a good arrangement. The gauge-reader’s -quarters are close to the off-take and he will not keep going down to -the gauge. Moreover an official coming along the main channel cannot see -the gauge. The gauge should be close to the head and in a gauge well -where oscillations of the water are reduced to very small amounts. The -upstream gauge requires no well.[25] - - [25] For further details as to gauges see Appendix G. - -All gauges should be observed daily, in the morning, and the reports -sent by canal dak, post or wire at the earliest possible moment. This -should be rigidly enforced. The register should be posted and laid -before the Subdivisional Officer daily with the least possible delay. It -is only in this way that the Subdivisional Officer can keep proper -control of the water, and detect irregularities. Sometimes trouble -arises owing to the gauge reports not coming in regularly. The -suboverseer can be made responsible for seeing to this matter as regards -all the gauge readers in his section. Gauge readers often reduce the -supply in a branch or distributary at night for fear of a rise occurring -in the night and causing a breach. This is to save themselves the -trouble of watching at night. They are also bribed to tamper with the -supply and run more or less in any channel or keep up the supply for a -longer or shorter time. All regulation should be rigorously checked by -the suboverseer, zilladar and Subdivisional Officer. Irregularities can -be speedily detected if proper steps are taken such as going to the -regulator unexpectedly. The watermarks on the banks can also be seen. If -any man is found to have delayed entering a gauge reading in his book or -despatching the gauge report it is evidence of an intention to deceive. -The suboverseer or zilladar should be required to enter in his note-book -all the checks he makes and the Subdivisional Officer should see the -entries and take suitable steps. - -There was formerly a general order in the Punjab that the Subdivisional -Officer should write the gauge register with his own hand. Such an order -is not now considered necessary nor has the Subdivisional Officer, -now-a-days, time to comply with it. The register should however be -written by the clerk carefully and neatly and not be made over to anyone -else. - -The regulation should usually be so effected that rushes of water in any -portion of the channel are avoided, but if scour occurs in a particular -part of the channel it may be necessary to try and obtain slack water -there. Until it is proved by experience that they are unnecessary, -soundings should be taken periodically downstream of large works. When a -branch or escape is closed the leakage should be carefully stopped. The -necessary materials should be always kept ready in sufficient quantity. - - -3. =Gauge Readings and Discharges.= For the head gauge of each -distributary and for certain gauges in the canals, discharge tables, -based on actual observations, are prepared. If changes occur in the -upper part of a channel, the discharge corresponding to a given gauge -reading is altered. One remedy for this is to have a second gauge -downstream of the “silt wedge” or scoured or narrowed reach. The indents -are then made out with reference to the second gauge, but any slight -adjustments due to fluctuation in the water level of the canal, are -effected by means of the head gauge. Unless the zilladar and -Subdivisional Officer are on the alert, the gauge reader is likely to -evade going to the lower gauge every morning, and to enter fictitious -readings for it, inferring them from the readings of the head gauge. If -there are any outlets between the two gauges, their discharge has to be -observed or estimated and added to the discharge of the distributary as -entered in the table corresponding to the readings on the second gauge. -The above system can be worked with advantage in cases where the -distributary bifurcates two or three miles from its off-take. The men in -charge of the two regulators can work together, one of them or an -assistant, going daily from one regulator to the other and back. - -Usually, however, the vitiating of the discharge table at the head gauge -has to be faced, and the table to be constantly corrected. It is -impossible to frame beforehand any rule or formula which would give a -certain correction for a certain depth of silt deposit. Moreover, there -might or might not be a contraction of the channel due to deposit on the -sides. The usual plan is to observe a discharge some time during each -month. If the result is in excess of the tabular discharge, all the -discharges for that month are increased in the same proportion. They can -be booked according to the table and totalled, and the correction -applied to the total. - -Discharges of canals and branches at their heads or at the boundaries of -divisions, are observed by the Subdivisional Officer about once a month. -Discharges of distributaries are observed about once a month, usually by -zilladars. They are also to some extent observed by the Subdivisional -Officer, but much is left to his discretion. Delta is worked out for -each distributary month by month, and also, of course, for each crop. -Thus a general duty “at distributary heads” can be obtained, and may be -used in new projects[26] instead of the duty at the canal head, -allowance being made for the water lost by absorption in the canal and -branches. - - [26] See CHAP. IV., Art. 2. - -It cannot be said that these important figures are obtained as carefully -as they could be. If the Subdivisional Officer personally observed the -discharge at each distributary head, even every other month, the -reliability of the results would be much increased. In addition to this -the discharges of canals and branches at the boundaries of subdivisions -should be observed and the results compared with the distributary -discharges, so as to show the loss by absorption. At first grave -discrepancies among the results would be found, but they would be -reduced as the causes of error became known. For the method of -investigating the causes of discrepant discharges see _River and Canal -Engineering_, CHAP. III., Art. 5. - -A specimen of a Subdivisional Officer’s gauge register is given in table -I. The zilladar keeps a similar register. The columns headed G contain -the gauge readings, those headed D the discharges. Until some years ago -there were no columns for discharges. The daily discharges of the canal -and of the branches at their heads--and at intermediate points if they -were at the boundaries of divisions--were entered in the Executive -Engineer’s office and the duty was worked out at the end of each crop. -The zilladar merely indented for a certain gauge reading at the -distributary head, and the Subdivisional Officer could tell pretty -nearly what gauge reading he required in the canal at the beginning of -his subdivision. Since the year 1900 or thereabouts, the zilladars have -been required to learn a good deal about discharges. They have to know -how to observe the discharge of a distributary, and to learn how the -discharge of an outlet varies with the head or difference between the -upstream and downstream water levels. They are supposed to indent for -certain discharges, and not merely for certain gauge readings. All this -knowledge is useful to the zilladars and tends to increase their -efficiency, but a practice of constantly thinking in discharges instead -of in gauge readings is unnecessary. If the channels were of all sorts -of sizes matters would be different. Actually the size of a channel is -apportioned to its work, and the proportion of its full supply which it -is carrying at any moment is easily grasped by means of gauge readings -alone. - -TABLE I--GAUGE AND DISCHARGE REGISTER. - - --------------+-----+--------------------------------------- - October, 1912.| | Main Line, Upper Bari Doab Canal. - | +-------------------------+------------+ - | | Tibri Regulator | Dhariwal | - | +-----+---------+---------+------------+ - | |Above| Main | Kasur | Nangal | - | | | Canal | Branch |Distributary| - | +-----+----+----+---------+-----+------+ - |Date.| _G._|_G._|_D._|_G._|_D._| _G._| _D._ | - | |-----+----+----+----+----+-----+------+ - | | | | | | | | | - | | | | | | | | | - | 1 | | | | | | 4·0| 100 | - | 2 | | | | | | 4·0| 100 | - | 3 | | | | | | 4·0| 100 | - | * | * | * | * | * | * | * | * | - | 29 | | | | | | 4·2| 110 | - | 30 | | | | | | 4·2| 110 | - | 31 | | | | | | 4·2| 110 | - --------------+-----+-----+----+----+----+----+-----|------+ - Total | | | | | |127·1| 3255 | - --------------------+-----+----+----+----+----+-----|------+ - No. of days in flow | | | | | | 31 | 31 | - --------------------+-----+----+----+----+----+-----+------+ - Average | | | | | | 4·1| 105 | - --------------------+-----+----+----+----+----+-----+------+ - - --------------+-----+------------------------------------------------ - October, 1912.| | Main Line, Upper Bari Doab Canal. - | +------------+----------------------------------- - | | Kunjar | Aliwal Regulator - | +------------+-----+---------+---------+--------- - | | Kaler |Above|Amritsar | Lahore |Escape - | |Distributary| | Branch | Branch | - | +------+-----+-----+----+----+----+----+----+---- - |Date.| _G._ | _D._| _G._|_G._|_D._|_G._|_D._|_G._|_D._ - | |------+-----+-----+----+----+----+----+----+---- - | | | | | | | | | | - | | | | | | | | | | - | 1 | | | | | | | | | - | 2 | | | | | | | | | - | 3 | | | | | | | | | - | * | * | * | * | * | * | * | * | * | * - | 29 | | | | | | | | | - | 30 | | | | | | | | | - | 31 | | | | | | | | | - --------------+-----+------+-----+-----+----+----+----+----+----+---- - Total | | | | | | | | | - --------------------+------+-----+-----+----+----+----+----+----+---- - No. of days in flow | | | | | | | | | - --------------------+------+-----+-----+----+----+----+----+----+---- - Average | | | | | | | | | - --------------------+------+-----+-----+----+----+----+----+----+---- - -As regards the weekly indents, the dealing with discharges instead of -gauge readings is of little practical value. The zilladar merely knows -that on some outlets the demand is great, on others moderate, and he -judges that the distributary needs say, 4 feet of water, its full supply -gauge being 5 feet. He cannot tell how many cubic feet each outlet -requires. If he is required to indent in cubic feet per second (he is -not always required to do this) he probably gets at the discharge from -the gauge reading, and not the gauge reading from the discharge. As -regards the general indent made by the Subdivisional Officer, the same -remarks apply. He can probably tell what gauge he requires without going -into discharges. - -Regarding the working out of delta month by month, not only are -discharges more or less doubtful, but the area irrigated is seldom -correct till near the end of the crop. However, the figures, towards the -end of a crop, may be useful. If delta on any distributary is higher -than is usual on that distributary, it may be desirable, if the supply -in the whole canal is short, to reduce the supply to that distributary -somewhat, but this remedy can be properly applied after the end of the -crop by altering the turns (Art. 5). Any steps in the direction of -altering outlets can only be taken after the end of the crop. Admitting, -however, that the working out of delta during the crop is useful, it can -be done by adding up the gauge readings for the month and taking the -average reading and the discharge corresponding to it. This is not quite -the same as the average of the daily discharges, but the difference is -small, and there would be a wholesale and most salutary saving in -clerical work. All the columns headed D could be omitted. The handiness -and compactness of the register would be vastly increased. The -discharges are only approximately known, and refinements of procedure -are unnecessary. The correction of the discharge table, by means of -observed discharges, once a month, can of course be effected without -booking the daily discharges.[27] - - [27] There should, in any case, be a special place in the gauge - register for showing the discharge tables, with a note of the - discharge observations from which the table was framed or in - consequence of which it was altered. - -Supposing the columns D to be retained the calculations of delta can be -made as shown in table II. the form being printed in the gauge book. To -facilitate the adding up of the discharges a line can be left blank in -table I. after each ten days, and the total for the ten days shown on -it. If the column D is not retained, the gauge readings can be added up. -The discharge corresponding to the mean gauge reading of the month, -multiplied by the number of days the distributary was in flow, gives the -figure to be entered in column 2 of table II. - -The final working out of delta crop by crop is of course of the greatest -value. The point which needs attention is, as already remarked, greater -accuracy in the discharges. For reasons which have already been given -(CHAP. I., Art. 5, and CHAP. II., Art. 9) the values of delta on -different distributaries will never be the same, but the causes of high -values can always be investigated and, to some extent, remedied. - -TABLE II.--CALCULATION OF DELTA FOR RABI, 1912-13, NANGAL DISTRIBUTARY. - - ------+------------+------------+---------+------+------------------ - Month.| Total of | No. of days|Irrigated| Delta| Remarks. - | discharges | in flow. | area up | up to| - +------+-----+------+-----+ to date.| date.| - | For |Up to| For |Up to| | | - |month.|date.|month.|date.| | | - ------+------+-----+------+-----+---------+------+------------------ - | | | | | Acres | Feet | - Octo- | 3255 | 3255| 31 | 31 | 6510 | 1·0 | - ber | | | | | | | - | | | | | | | - Novem-| 3390 | 6345| 27 | 58 | 9000 | 1·41 |Closed 3 days - ber | | | | | | |because of breach. - ------+------+-----+------+-----+---------+------+------------------ - - -4. =Registers of Irrigation and Outlets.= It is obvious that a -Subdivisional Officer cannot look properly into matters connected with -the working of his channels unless he has, ready to hand, a register -showing, crop by crop, the area irrigated by each distributary and each -outlet and keeps it posted up to date. In 1888 the Chief Engineer of the -Punjab Irrigation directed that each Subdivisional Officer should keep -up English registers of irrigation by villages. The order was for years -lost sight of. The matter has lately, in view of certain recent -occurrences on a large perennial canal, again come to notice, and this -most essential factor in the working of a canal is, it is believed, -receiving attention. - -As to the precise form which an irrigation register should take, -opinions and practices differ somewhat. In all cases the net irrigated -areas should be shown--kharif, rabi, and total--and the total remitted -area. The areas remitted for kharif and rabi separately may or may not -be shown. The net percentage of the commanded culturable area -irrigated--total of the two crops--can be shown in red ink and is most -useful.[28] It enables the general state of affairs on any outlet to be -seen at a glance and shows how it compares with other outlets and with -the whole distributary. - - [28] Provided that the culturable commanded area is properly shown and - is not made to include jungles or other tracts which were never - intended to be irrigated. - -Besides the irrigation figures it is necessary to record for each outlet -its chainage, size of barrel[29] and commanded culturable area. In the -case of a distributary which has been working for years, and on which -the outlets are undergoing few alterations, it may be suitable to record -the above items in a separate “outlet register,” and to give in the -irrigation register a reference to the page of the outlet register. But -even in such a case alterations will have to be made from time to time -in the outlet register and there is great danger of its becoming spoilt, -imperfect or unintelligible. In the case of a distributary on which the -outlets are undergoing frequent changes, the items under consideration -should be shown crop by crop, and also the material of the outlet--wood -or masonry--and the width and mean height of the barrel. In no other way -can the working of the outlet be properly followed and understood. It is -probable that this procedure is the best in every case, _i.e._, even -when the alterations made are not frequent. By arranging the register as -shown in table III. the repetition of the entries, when they undergo no -alteration, is avoided, only dots having to be made. - - [29] The sizes of the outlets should be measured by the suboverseer - and some checked by the Subdivisional Officer and the correct - sectional area, as actually built, entered. - -The specimen shows only two outlets on a page, and covers five years, -but three outlets can easily be shown on a large page, and the period -can be seven years. If there are more than three outlets in the village, -the lowest part of the page shows the total of the page instead of the -total of the village, and the other outlets are shown on the next page, -the grand total for the village coming at the foot. - -TABLE III.--REGISTER BY OUTLETS AND VILLAGES. - - Distributary .................................. - ------------+-------+------------------------------------------------+ - | | Information regarding outlet. | - | |--------+--------+---------+--------------------+ - | | | | |Dimensions of barrel| - Name and | | | |Sectional+----------+---------+ - description| Year |Chainage|Material| area of | | | - of outlet. | | | | barrel. | Width | Height | - | | | |(minimum)| | | - ------------+-------+--------+--------+---------+----------+---------+ - Register no.| | | | | | | - |1902-03| | | | | | - Name |1903-04| | | | | | - |1904-05| | | | | | - Bank |1905-06| | | | | | - |1906-07| | | | | | - Flow or lift| | | | | | | - ------------+-------+--------+--------+---------+----------+---------+ - Register no.| | | | | | | - |1902-03| | | | | | - Name |1903-04| | | | | | - |1904-05| | | | | | - Bank |1905-06| | | | | | - |1906-07| | | | | | - Flow or lift| | | | | | | - ------------+-------+--------+--------+---------+----------+---------+ - Total } |1902-03| | | | | | - of } |1903-04| | | | | | - |1904-05| | | | | | - {Village |1905-06| | | | | | - { Page |1906-07| | | | | | - ------------+-------+--------+--------+---------+----------+---------+ - - Village .................................. - ------------+-------+------------------------------------------------- - | | Working of outlet. - | |------------------------------------------------- - | | Area in acres. | - Name and | |----------+--------+-----------------+ Net - description| Year | | | Net irrigated |irrigated, - of outlet. | |Commanded |Remitted|------+----+-----+per cent of - | |culturable| |Kharif|Rabi|Total|culturable. - ------------+-------+----------+--------+------+----+-----+----------- - Register no.| | | | | | | - |1902-03| | | | | | - Name |1903-04| | | | | | - |1904-05| | | | | | - Bank |1905-06| | | | | | - |1906-07| | | | | | - Flow or lift| | | | | | | - ------------+-------+----------+--------+-----------------+----------- - Register no.| | | | | | | - |1902-03| | | | | | - Name |1903-04| | | | | | - |1904-05| | | | | | - Bank |1905-06| | | | | | - |1906-07| | | | | | - Flow or lift| | | | | | | - ------------+-------+----------+--------+-----------------+----------- - Total } |1902-03| | | | | | - of } |1903-04| | | | | | - |1904-05| | | | | | - {Village |1905-06| | | | | | - { Page |1906-07| | | | | | - ------------+-------+----------+--------+-----------------+----------- - -All the outlets of the uppermost village on the distributary should be -entered, first, even though some of them may be downstream of, and bear -serial numbers lower than, the outlets of the next village. When one -outlet irrigates two or three villages the irrigation of the separate -villages can be entered on one page in the places usually allotted to -outlets, and the lowest part of the page can show the total for the -outlet, the necessary changes in the headings, etc. being made. If any -of the villages has other outlets these will appear on another page and -the total for the village can also be shown. - -The village totals should be posted into a second register prepared -somewhat as shown in table IV. and totalled. The totals show the -irrigation for the whole distributary.[30] If necessary the failed areas -can be shown in the register in red ink. If any village is irrigated -from two or more distributaries, each portion of the village should be -dealt with as if it was a separate village. - - [30] Very long channels, e.g. inundation canals from which direct - irrigation takes place, can be divided into reaches and the irrigation - of the reaches dealt with as if they were separate channels. A reach - should generally end at a bifurcation or stopdam. - -In all registers some blank spaces should be left for the insertion of -new outlets or new villages. The number of pages to be left will depend -on local circumstances, which should be considered. In case figures are -supplied by the revenue authorities and deal only with whole villages, -the details obtained by the canal staff should always be added up and -checked with them. Similarly the commanded culturable areas for the -outlets and villages should be added up and checked with the known total -for the distributary. - -TABLE IV.--ABSTRACT OF IRRIGATION BY VILLAGES AND CHANNELS. - - Canal...................... Distributary.............. - - From....................... To........................ - --------+------------+-----------+---------------------------------- - Name of |Commanded | | Net Areas Irrigated in Acres. - Village.|Culturable | Detail. +----+----+----+----+----+----+---- - |Area (Acres)| |1902|1903|1904|1905|1906|1907|1908 - | | | -03| -04| -05| -06| -07| -08| -09 - --------+------------+-----------+----+----+----+----+----+----+---- - | | Kharif | | | | | | | - | | Rabi | | | | | | | - | | Total | | | | | | | - | |Per cent of| | | | | | | - | |Culturable | | | | | | | - --------+------------+-----------+----+----+----+----+----+----+---- - | | Kharif | | | | | | | - | | Rabi | | | | | | | - | | Total | | | | | | | - | |Per cent of| | | | | | | - | |Culturable | | | | | | | - --------+------------+-----------+----+----+----+----+----+----+---- - | | Kharif | | | | | | | - | | Rabi | | | | | | | - | | Total | | | | | | | - | |Per cent of| | | | | | | - | |Culturable | | | | | | | - --------+------------+-----------+----+----+----+----+----+----+---- - | | | | | | | | | - Total | | | | | | | | | - | | | | | | | | | - -The percentages of culturable commanded area irrigated by different -outlets will, as already explained, always show discrepancies. Any -special causes of low percentages, e.g. a large proportion of rice, can -be briefly noted in the register. - -On inundation canals, and some others, the alignment and chainage are -liable to undergo alteration. In such cases it is best to adhere to the -original chainage until all the alterations in alignment have been -carried out. - - -5. =Distribution of Supply.= The question how the supply of a canal is -to be distributed when it is less than the demand, is not always very -simple. Suppose that the main canal, after perhaps giving off several -distributaries, divides, at one place, into three branches, A, B, and C, -whose full supply discharges are respectively 2,500, 2,000 and 1,500 c. -ft. per second. Suppose that the total discharge reaching the -trifurcation is expected to be, when at the lowest during the crop, only -2,200 c. ft. per second, instead of 6,000. It would be possible, -supposing the discharge tables to be fairly accurate, to keep all the -channels running with discharges proportionate to their full supplies, -but this would not be suitable. The water levels would not be high -enough to enable full supplies to be got into the distributaries, or at -least into some of them. Moreover, the running of low supplies causes -much loss by absorption. The plan usually adopted is to give each -channel full supply, or nearly full supply, in turn, and for such a -number of days that the turn of each branch will recur about once a -fortnight, that being a suitable period having regard to the exigencies -of crops, and having the advantage that the turn of each branch comes on -a particular day of the week, so that everyone concerned, and -especially the irrigating community, can remember and understand it. -Table V. shows how the turns in the above case can be arranged. The -figures show the discharges. - -TABLE V. - - ---------+------+------+------ - DAY. | A | B | C - ---------+------+------+------ - 1 | 2,200| | - 2 | 2,200| | - 3 | 2,200| | - 4 | 2,200| | - 5 | 2,200| | - 6 | | 2,000| 200 - 7 | | 2,000| 200 - 8 | | 2,000| 200 - 9 | | 2,000| 200 - 10 | | 2,000| 200 - 11 | 700| | 1,500 - 12 | 700| | 1,500 - 13 | 700| | 1,500 - 14 | 700| | 1,500 - ---------+------+------+------ - Total |13,800|10,000| 7,000 - | | | - Correct | | | - discharge|12,800|10,300| 7,700 - according| | | - to Full | | | - Supply. | | | - ---------+------+------+------ - -The orders given to the gauge readers in these cases are simple, namely -to give each branch full supply in turn, and to send the rest of the -water down the channel next on the list. - -The number of days allotted to the larger branches are greater than to -the smallest because this will probably be simplest in the end, and also -because the number of distributaries on a larger branch is likely to be -greater, and the allotment to the distributaries is thus facilitated -somewhat. Each branch receives water in one period of consecutive days. -Any splitting up of the turn would be highly objectionable. It would -cause waste of water, and would give rise to much difficulty in -redistributing the supply among its distributaries. Each branch receives -its residuum turn before it receives its full supply turn. The advantage -of this is that water is not let into the channel suddenly. The total -supplies of A, B and C are in the ratio of 13·8, 10, and 7, and not, as -they should be 12·8, 10·3, and 7·7, but no closer approximation can be -got. If the number of days of full supply allotted to each branch is -changed, or if the residuum from C is given to B, instead of A, the -relative total discharges differ still more from what they should be. - -If now the total supply is supposed to be increased to 2,700 c. ft. per -second, the discharges are as shown in table VI. - -TABLE VI. - - ----------+-------+-------+----- - DAY. | A | B | C - ----------+-------+-------+----- - 1 | 2,500 | 200 | - 2 | 2,500 | 200 | - 3 | 2,500 | 200 | - 4 | 2,500 | 200 | - 5 | 2,500 | 200 | - 6 | | 2,000 | 700 - 7 | | 2,000 | 700 - 8 | | 2,000 | 700 - 9 | | 2,000 | 700 - 10 | | 2,000 | 700 - 11 | 1,200 | |1,500 - 12 | 1,200 | |1,500 - 13 | 1,200 | |1,500 - 14 | 1,200 | |1,500 - ----------+-------+-------+----- - Total |17,300 |11,000 |9,500 - | | | - Correct | | | - Discharge.|15,700 |12,600 |9,500 - ----------+-------+-------+----- - -Considering both the above tables, A always receives more water than its -share, while B and C on the whole receive too little. Considering table -V. by itself, matters might, perhaps, be set right by altering the total -number of days from 14 to 13 or 12, but this, besides being somewhat -objectionable for the reason already given, might not improve matters -when table VI. came into operation. It is desirable to avoid frequent -changes or complicated rules. It is objectionable to make any turn -consist of other than a whole number of days. The shifting of the -regulator gates is begun at sunrise, a time when officials are about and -can see what is happening. All gauges are read early in the morning, and -those at regulators are read after the regulation has been done and the -flow has become steady. If any regulation were done in the evening, the -entry in the gauge register of that day would convey a wrong impression, -and the discharge would be incorrectly booked. Moreover, any system of -regularly booking evening as well as morning gauges leads to swelling of -the already voluminous gauge register. - -The best method of adjusting matters is to make slight alterations in -the full supply gauges. Suppose the normal full supplies in all three -branches to be 6 feet. When table VI. is in operation the full supply of -A can be reduced to about 5·8 feet. This would give, during the first 5 -days, less water to A and more to B, and there is the further advantage -that a very small supply, 200 c. ft. per second, is not run in any -branch. As regards table V., branch A never receives full supply. This -is a rare case.[31] If it were safe, as it might be, to run slightly -more than full supply in C, this could be done, and it would increase -the supply in C during the last four days and reduce that in A. -Otherwise a certain gauge would have to be fixed for A which would give -it less than 2,200 c. ft. per second during the first 5 days, and the -balance would go to branch B. Similarly, the gauge of B could be -slightly reduced, and this would increase the balance going to C. The -orders given to the gauge reader are, as before, to send the full supply -down one channel, and the balance to the next. The only additional -procedure necessary is to inform the gauge reader from time to time what -the full supply gauges are. In any case such information has probably to -be conveyed to him at times because the channels undergo changes, and -the discharge corresponding to a given gauge also changes. - - [31] The total discharge, 2,200 c. ft. per second, assumed, is very - low compared with the full supply of 6,000 c. ft. per second. - -When the discharge of the canal exceeds 3,500 c. ft. per second there -is, when B and C are receiving water, a second residuum, which goes to -A. Tables can be worked out for several discharges of the main canal, -but it is the minimum discharge which is the most important factor in -the case. The minimum discharge, or something very near it, generally -lasts through about half the crop, and it is when the supply is at a -minimum that care and justice in the distribution are most needed. - -The chief objection to the arrangements above described is that the -surplus to be sent down one channel or another is sometimes so small -that it must be to a great extent wasted. The best means of preventing -this is to have the discharge tables, including one for the main canal -at some point higher up than the trifurcation, constantly corrected. In -that case, it is known under what circumstances a small surplus will -occur, and the orders can be modified so as to prevent its occurrence. -The orders will of course be more complicated, and will have to be dealt -with by an engineer and not a gauge reader. - -The turns, once satisfactorily arranged, may go on for years without -alteration. They may require altering if any branch is found, in the -course of time, to be doing worse than or better than the others, though -the correction can probably be made by altering the full supply gauge. - -The turns of the branches having been arranged, it remains to settle -those of the distributaries. The total available discharge being, as -before, assumed to be rather more than one-third of the full supply -discharge, each distributary taking off from the main canal, where it is -not possible or not desirable to regulate the height of the water level -in the canal, can be run with full supply for four or five days out of -each fortnight, and then closed. Whether it be four days or five may -often depend on special circumstances such as whether the distributary -is doing well or otherwise. If necessary the full supply can be -adjusted. When the canal supply increases the four or five days can be -increased. - -The same principle can be adopted for any distributary whose off-take is -in the upper part of a branch, _i.e._, where the branch is many times -larger than the distributary, and where it is not possible or not -desirable to regulate the water level of the branch. For a distributary -further down the branch, the turns of branch and distributary can be -arranged as explained above for a canal bifurcation. The orders given to -the gauge reader are, as before, to give the channel whose turn it is, -full supply and to send the balance down the other channel. When the -turn of distributary is over it becomes the turn of the branch. The -distributary would not be closed if this would cause the full supply in -the branch to be exceeded. Care must be taken that every distributary -receives full supply during part of the time when the branch is -receiving full supply. If its turn came only when the branch was -receiving a residuum supply, or rather when the residuum supply was -reaching the distributary off-take--for in the case of a distributary -whose off-take is far down a long branch the two things are not the -same--it might, in the event of the supply in the main canal falling -exceptionally low, receive no water at all. - -The time taken by a rise in travelling down a canal is very much the -same as that taken by a fall and each takes effect more or less -gradually. When a branch receives, at any point, a temporary increase in -its supply, owing to the closure of a distributary for, say, three -days, there will be a rise lasting for three days at a point further -down. The rise will take some time to come to its height, and some time -to die away. There will be about three days from the commencement of the -rise to the commencement of the fall, or from the end of the rise to the -end of the fall. If, either in the main canal or in a branch, there is -any distributary into which full supply cannot be got, its turn can be -increased accordingly. Owing to the shortness of the turns, and to -allowance having to be made for the time occupied by rises and falls in -travelling down the branch, the fixing of the turns for distributaries -near the tail of the branch requires a good deal of consideration. -Matters are facilitated by making a sketch (Fig. 25) in which the widths -of the channels, as drawn, are roughly in proportion to the full supply -discharges. If 14 copies of the sketch are made the arrangements for -each day can be shown on them, full supply being shown black and -residuum hatched. Distributaries would be shown as well as the main -channels. - -[Illustration: FIG. 25.] - -The irrigation registers of course show how the irrigation of the -different channels is going on from year to year and if changes in the -turns become necessary they can be effected. - -After the water has entered the watercourses the canal officials have -nothing to do with its distribution. The people arrange among -themselves a system of turns, each person taking the water for a certain -number of “pahars”--a pahar is a watch of three hours--or fractions of a -pahar. The zilladar can however be called in by any person who has a -dispute with his neighbour. If the matter is not settled the person -aggrieved can lodge a formal complaint and a canal officer then tries -the case, and if necessary punishes the offender. - -In former days it was usual, in some places, for no regular turns to be -fixed for the distributaries, orders being issued regarding them from -time to time. The weak point about any such plan is that in the event of -the controlling officer delaying, owing to any accident, to issue an -order, no one knows what to do. Orders were also sometimes issued to -zilladars giving them discretionary powers in distribution. No one would -now issue such orders. The essential principle is to remove power from -the hands of the subordinates. The working of the main channels by turns -and the construction of outlets of such a size that they never require -closure, has resulted--in places where such matters are attended to--in -the absolute destruction of such power.[32] The only way in which a -zilladar can injure anyone is to say that water is not in demand. This -would however result in damaging the whole of the villages in his -charge. He is not likely to do this. - - [32] In the printed form lately in use in the Punjab for reports on - zilladars, one of the questions asked is whether “his arrangements” - for the distribution of water are satisfactory, as if that was still - considered to be the zilladar’s business. - -In case the supply is wholly or partially interrupted owing to a breach -or an accident at the headworks, or other cause, one particular branch -or distributary may lose its turn or part of it. If its loss is not -great it may be best to allow the turns to take their usual course, but -otherwise they should be temporarily altered in such a way as to -compensate the channels which have suffered. - -On inundation canals the water at a regulator is sometimes headed -up,--all branches being partially closed--in order to give more water to -outlets in the upstream reach. There are even some regulators--or rather -stop-dams--constructed solely for this purpose at places where there is -no bifurcation of the canal or distributary. Any such heading up should -be planned out beforehand and days for it fixed, and also the gauge -reading. If the water, without any heading up, rises to the needful -height on the gauge, nothing has to be done. There are also places on -inundation canals where the land is high and is only irrigable during -floods. At such places it is usual, on some canals, to allow the people -to make cuts in the bank when the water attains a certain height. Owing -to the high level of the country, nothing in the nature of a breach can -occur. In one canal division where the above arrangement was in force, -the people used to send applications to the Executive Engineer for leave -to cut the banks. This resulted in much delay. A list was prepared -showing exactly where the banks might be cut, the people were informed -and the formalities were much reduced. - - -6. =Extensions and Remodellings.= An existing canal or distributary may -need remodelling for various reasons, and in various degrees. If the -velocity is too high and the bed has scoured, or the sides have fallen -in, it may be necessary to raise the crests of falls, or to construct -intermediate weirs, or to widen the channel and reduce the depth. If the -command is not good it may be necessary to regrade the channel. If silt -deposit occurs, the cross-section of the channel may have to be altered, -to give a better relation between D and V. If there is surplus water, -extensions or enlargements of channels may be desirable and these can -sometimes be undertaken to a moderate extent merely by restricting a -somewhat too lavish supply to existing distributaries. If the water -level is dangerously high it may have to be lowered, or the banks raised -and strengthened. Sometimes it is desirable to cut off bends either to -shorten the channel and gain command or because the bends are sharp and -cause falling in of the banks or, if numerous, silting. In all cases the -general principles are the same as for entirely new projects, but -certain details require consideration. - -The distributaries of the older canals were constructed before Kennedy’s -laws regarding silting were known, and it has been necessary to remodel -many of them. In some cases the gradient was wrong, in others the -cross-section.[33] In some cases a distributary ran in rather low -ground, and it was proposed to abandon it and construct a new one on -high ground. It was however pointed out by Kennedy (_Punjab Irrigation -Paper No. 10_, “Remodelling of Distributaries on old Canals,”) that -irrigation had become established along the course of the distributary, -that most of it would remain there and that a new alignment would result -in increased length of watercourses. Such distributaries have therefore -been allowed to remain very much as they were. - - [33] The difficulty of reducing the size of a channel which is too - large is well known and has been discussed in _River and Canal - Engineering_, Chapter VIII. It is there explained that a moderate - reduction of width can be effected by “bushing,” but that for great - reductions, groynes or training walls are necessary. When the bed of a - distributary is too low it has been suggested that it could be raised - by filling in earth in each alternate length of 500 feet, and leaving - the rest to silt, but this would be expensive. - -Remodelling should not be considered piecemeal, but regard should be had -to the whole channel. When a distributary is remodelled the outlets -should of course be dealt with as well as the channel. The chief thing -to consider is not whether the channel as it exists is exactly as it was -originally designed to be, but how it is doing its work and what kind of -alteration it needs. Even when a simple silt clearance or berm cutting -of a channel has to be undertaken, the work need not always consist in -blindly restoring the channel to its original condition. It may be both -feasible and desirable to remodel it to a slight extent, lowering the -water for instance in reaches where the outlets draw off very good -supplies and thus benefiting less fortunate reaches lower down. - -The irrigation boundaries of the extended or remodelled channel should -as far as possible follow drainages, but these are not always important -or pronounced. The actual irrigation boundaries should be shown and also -those of any neighbouring channels of other canals, and any suitable -adjustments should be made. - -Regarding the percentage of area to be irrigated, it has already been -stated that one canal or distributary irrigates a far higher percentage -than another. Generally when there is a high percentage in any tract, it -is undesirable to cut it down unless it has very recently sprung up to -the detriment of other tracts. In some remodelling projects a uniform -percentage is taken on the whole area including both new and old -irrigation. This plan is suitable when the percentage of old irrigation -is not very high. In other cases the old irrigation to be provided for -may be taken as the maximum area actually irrigated, a little being -perhaps added for extensions. If the irrigation of considerable areas of -jungle tracts is contemplated and if these consist of numerous small -patches, a further percentage can be added for them. If there are large -jungle tracts they can of course be dealt with separately and any -suitable percentage adopted for them. The percentage for each portion of -a remodelling project is not necessarily the same. - -If the discharge of a channel is increased, the waterways of bridges may -need increasing. This can often be done (Chapter II., Art. 12) by making -a floor at a low level. Or the waterway may be allowed to remain small, -the floor being added at the bed level and the bridge then becoming an -incomplete fall, (page 87). The fall in the water surface, though small, -can be recognised and shown on the longitudinal section. - -In remodelling schemes, the longitudinal section should give all -possible information. It should show not only the levels of bed and -banks, but the F.S. levels (in blue figures) above and below all falls -or regulators, and the levels of floors and waterways of bridges. The -plan should show all watercourses and the “chaks” or areas assigned to -them.[34] On each chak the actual average irrigation can be shown in -blue figures and the proposed irrigation in red. The “draw-off” for each -proposed outlet can then be shown on the longitudinal section. The area -actually irrigated, as shown on the map, should in each case be the -mean of at least three years, and if possible of five years. The number -of years should be mentioned in a note on the map. Cross-sections of -channels should always be drawn to natural scale, and not with the -horizontal scale differing from the vertical. - - [34] The field maps mentioned on page 101 are prepared to a very large - scale and show all watercourses. The maps should always be corrected - up to date by the patwaris. The chak maps which are on a smaller - scale--say 4 inches to the mile--can thus be kept correct. - - -7. =Remodelling of outlets.= When a channel is remodelled, the -remodelling of the outlets may consist in alterations of the number or -sites or in alterations of their sizes. - -Regarding the former, a map should be prepared showing all watercourses, -chaks and contours.[35] On this map new lines for the watercourses can -be shown, the principles enunciated in Chapter II., Art. 9, being -generally followed, but in such a way as to utilise existing -watercourses and outlets as far as possible. The work often consists in -the abolition of a certain number of watercourses, when these are too -close together and run parallel to one another. There may, however, be -little gain in amalgamating two such watercourses if they serve two -different villages. There is nothing to prevent the people from dividing -the watercourse into two as soon as it gets away from the canal, and -they are likely to do this in many cases. When one branch has a flatter -slope than the other it would lose command if it took off further down. -The people on the steeper branch might not agree to using the flatter -one because of silt trouble, or increased height of embankment. In a new -project it is not difficult to get the people to do what is needed, but -when once irrigation has become established it is often difficult to get -suitable changes made. The advantages of amalgamating watercourses, -though appreciable, have been a good deal exaggerated. The chief -advantage is gained by reduction in the sizes of outlets. Then, however -many branches the watercourse may have, they can only run in turns and -not all together. It may happen that two watercourses, though taking off -near one another, run in different directions and that the chaks are of -suitable shapes and sizes. In such a case the only advantage of -amalgamating is that it saves an outlet in the canal bank. No saving in -the length of watercourse will be effected because there will be a -bifurcation as soon as the watercourse leaves the canal boundary. If -both outlets are of suitable design and proper size or require only -slight alteration, both can remain but otherwise amalgamation can be -effected. In some cases amalgamation might give a discharge greater than -that usually allowed for an outlet but this need form no obstacle. The -chief reason for limiting the discharge is the alleged inability of the -farmers to manage a large channel. This matter is exaggerated as already -stated (page 74). In the case under consideration it obviously makes no -difference whether there are two watercourses each discharging 5 c. ft. -per second, or one discharging 10 c. ft. per second, and immediately -dividing into two. Very small watercourses should, when possible, be -joined to others but if there is no other near enough they must -generally remain, however small they may be. - - [35] In small remodelling schemes the lines of existing watercourses - show how the country slopes, and a contour plan is not a necessity. - -Regarding the alterations in sizes of outlets, whether or not there are -alterations in their number and position, information as to the actual -duties on the watercourses should be obtained. The discharge of the -watercourses should be observed several times and added up and checked -with the discharge of the distributary. The areas irrigated are known -from the irrigation register. If the duties are abnormal the causes can -be gone into, and a judgement can be formed as to how far they will -remain in existence, and whether any watercourse is often kept closed. -If so the outlet is too large. The duties, modified so far as may seem -desirable, can be used for calculating the sizes of the remodelled -outlets. But alterations of the sizes after a year or two years’ working -will probably be necessary. The above procedure is also applicable to a -case where the old watercourses had no masonry heads but were merely -open cuts as on some inundation canals. - -A common case is that in which the channel is not remodelled--or at -least its water level remains very much as before--but merely the -outlets are altered in number, position or size, or in any or all of -these. If the land irrigated by an outlet is high, the irrigation may be -far short of what was expected, and the size of the outlet may have to -be increased or its site shifted, generally upstream. This is often done -at the request of the people, and at their expense.[36] - - [36] On some of the more modern canals the people are not allowed to - pay for outlets, so that no question of ownership can arise. - -Old outlets should always be removed when superseded by others. -Otherwise they are apt to be reopened or claims set up regarding them. - -Near the tail of a channel the discharge of an outlet may be an -appreciable fraction of that of the channel. In such a case the -adjustment of the size of the outlet, and that of the channel or of any -weir or fall in the channel, should be considered together, the -irrigation on the outlet and that on the channel downstream of it being -compared. And similarly as to the sizes of any two or more tail outlets. -Such outlets are sometimes left without masonry heads on the ground that -this injures no one. It may injure an outlet upstream of them by drawing -down the water. Tail outlets often need constructing or reducing in size -to raise the water level in the reach upstream of them. - -Whenever the size of an old outlet is altered the design should be -altered if unsuitable. The parapets should be brought into proper line, -the roadway corrected, the floor level adjusted and any splayed wing -walls abolished. If the outlet is skew it should be made square. All -this should also be done to all old outlets or heads of minors even if -the sizes are correct, whenever remodelling of outlets on any channel is -undertaken.[37] - - [37] Wherever an outlet is built or altered, a template, made to the - exact size of barrel required, should be supplied to the subordinate - in charge of the work. - -It was stated in Chapter II. that the construction of masonry outlets on -a distributary is not usually a final settlement of the matter. In many -cases a proper proportion of water does not reach the tail. Even in such -a case matters have occasionally been left alone, or the old and -pernicious system of closing the upper outlets has been resorted to. In -such circumstances the irrigation of a group of tail villages will be -found to be less than that of a group higher up, the people to some -extent acquiescing in the old idea that a tail village must be a -sufferer. Government, or at least the Irrigation Department, has no -particular direct interest in the matter. The total area irrigated, will -probably be very much the same in any case. But an engineer who takes an -interest in this part of his work will not allow matters to remain long -in the state described. He will, of his own accord, adjust the outlets -and equalise, as far as possible, the irrigated percentages. The people -will disturb matters to some extent by enlarging watercourses, but there -is a limit to this and it can be met by an occasional reduction of an -outlet. A distributary, when once its outlets have been carefully -adjusted, attains to something approaching perfection in its working. -Any excess in the supply is taken partly by the upper outlets but part -of it gets to the tail. Similarly any deficiency in the supply is -distributed over the channel. The outlets which have a poor command and -small head are most affected in either case. On the whole they do not -lose or gain more than the others. The working of such a distributary -causes great satisfaction to the engineer and not the least ingredient -in this is the knowledge that he has wholly destroyed the power of his -native subordinate. - -In an inundation canal division in the Punjab, some dozen -distributaries, varying in length from 5 to 28 miles, and with -discharges ranging up to 300 c. feet per second, were dealt with as -above in one season. The engineer in charge being specially desirous -that sufficient water should reach the tails, reduced the sizes of some -outlets too much. When an outlet of 1 or 2 sq. feet has to be reduced to -a small fraction of its size it is not easy to say what the fraction -shall be. Water reached the tails of all the channels in sufficient -quantity, in some cases in rather more quantity than was necessary. -When the irrigation register was examined, it was found that the general -results were entirely satisfactory. In a small proportion of cases -outlets had irrigated too little and had to be re-enlarged somewhat. -After a second season hardly any changes were needed. When any silt -clearance or berm-cutting seemed necessary the irrigation register again -came into play. If, for instance the tail outlets, as a whole, were -receiving too little water, enlargement of the upstream reaches was -effected with consequent lowering of the water level there. - -In the case above described the channels flowed for only five months in -the year. Some of them silted a good deal but as this silting was -roughly the same every year, it did not greatly affect the question of -outlet sizes. On a perennial distributary of which the head reach silts -during part of the year and scours during the other part, a proper -distribution of supply by adjustment of outlet sizes alone may be more -difficult. If the silt was frequently cleared, this would cause needless -expense and interference with irrigation. In cases where the -distributary is not run constantly, something can be done by attending -to the regulation. When there is silt in the head reach, the discharge -can be reduced and the period of flow proportionately increased. The -lowered water level reduces the supplies of the upper outlets, and -increases the discharges of those lower down. Moreover the periodical -silting and scour are not always serious. Also it is not essential that -the supply to each watercourse should be exactly the same every year. -There are always good and bad seasons. It is sufficient if a watercourse -is not allowed to suffer on the whole, and is never allowed to suffer -much. There is no doubt that it is possible to deal satisfactorily in -the above manner with very many distributaries. It is frequently -reported that “difficulty is experienced in getting water to the tail.” -This is owing to timidity in reducing the sizes of outlets. The suitable -plan is to reduce them to such an extent as to cause a proper supply to -reach the tail and then, if necessary to enlarge some. It has been -already remarked that only a short length of the barrel need be altered. -The cost of this is very small. The real difficulty in the case is not -the impossibility of securing good results, but the impracticability, in -many cases, of securing the constant attention which the procedure -demands.[38] - - [38] See also Chapter V. Art 3. - - -8. =Miscellaneous Items.= At the headworks of a canal there is a -permanent staff of men who work the gates and look after the works. They -assist in discharge observations and in reading the gauges, and they may -have to take soundings in the river to see what changes are taking -place. Some one is on watch day and night and reads the gauges at -frequent intervals. The officer in charge occasionally inspects the -works at night without notice. Detailed rules regarding the above -matters, and any others that are necessary owing to special local -conditions, are drawn up. Sometimes there is difficulty in getting the -staff to attend properly to the regulation of the supply in the canal at -night. Probably some “tell-tale” watches would be useful. They would at -least show the times at which the men concerned went to the gauges or -other points. - -At the headworks, and at all important regulators, a stock of concrete -blocks should be kept ready for the execution of any urgent repairs. - -Regarding the ordinary maintenance work on the channels, details are -given in Appendices B and C. Appendix D, reprinted from _Punjab Rivers -and Works_, contains rules for watching and protecting any banks or -embankments which require it. - -Silt clearances and berm cutting of channels have been mentioned in Art. -1. Special attention should be given to the accurate ranging of the -centre line. Otherwise the channel may become crooked. The great defect -in the earthwork ordinarily met with in the banks of canals and -distributaries is that the clods are not broken. In consequence of this -new banks are extremely liable to breach, and much trouble and expense -result. Sometimes a dam is thrown across a new distributary, and the -channel upstream of it is gradually filled with water, the bank being -watched and leakages made good. The dam is then shifted to a place -further down. In this way the banks are consolidated. - -When a distributary is closed for silt clearance or other work, if the -head regulator has planks and a double set of grooves, it is possible to -stop all leakage by filling in earth between the two sets of planks and -ramming it, but otherwise it is necessary to construct an earthen dam -just below the regulator. Upstream of the dam the water, owing to the -leakage through the planks, gates or needles, rises to the same level as -the water in the canal. Native subordinates have a remarkable aptitude -for allowing such dams to break while the work in the distributary is in -progress or before it is measured. Now and then the dam is wilfully cut. -The remedy is to make the dam of proper strength--the top should be 8 -feet wide and a foot above the water,--and to have it watched day and -night. - -At a bend in a channel there is often a silt bank next the convex bank, -and a hollow near the concave bank. The average bed level is probably -very much the same as in the straight reaches. Removal of the silt bank -is unnecessary, and if removed it quickly forms again. - -Any length of channel in which the depth of silt to be cleared is small, -say ·50 foot in a large channel and ·40 foot in a small one, should not -be cleared, provided its length is considerable (say 1,000 feet), and -that it is not close to (say within 3,000 or 2,000 feet from) the head -of the channel. Estimates should be prepared accordingly, the shallow -digging being struck out. Clearing a small depth of silt merely gives -contractors a chance of cheating by scraping the bed. - -If the watercourses at the tail of a distributary are silted, the people -should be pressed to clear them. Otherwise there will be heading up of -the water of the distributary, and silt deposit may result. - -When a channel is scoured, any regulator in it can be kept partly closed -so as to reduce the surface slope in the reach upstream of the regulator -and encourage the deposit of silt. A table should, in such cases, be -drawn up giving the gauge readings to be maintained at the tail of the -reach corresponding to given readings at the head. - -Various methods of protecting banks are described in _River and Canal -Engineering_, Chapter VI. The growing of plants on the inner slopes of -channels whose sides fall in, needs special attention. Some remarks on -this are given in _Punjab Rivers and Works_, Chapter II., Art. 3. A -specification for bushing is given in Appendix E of this volume. - -A Subdivisional Officer generally receives a steady stream of -applications from members of the irrigating community regarding--among -other matters--outlets or watercourses. Generally these applications are -made over to the zilladar to be reported on. In a large number of cases -the applicant states that the irrigation of his land or “holding” is not -satisfactory, or has fallen off, and sometimes he asks that it may be -transferred, wholly or in part, to another watercourse which he thinks -will give a better supply. In all such cases, and in some others, the -first requirement is a statement of the irrigation figures. The -irrigation register gives only the total for the watercourse. A printed -form should be prepared with spaces for showing the name of the -distributary, villages, watercourses, holdings and applicants concerned, -and the nature of the application. Below this is a form, prepared -somewhat as shown below. When this form is filled in, the state of -affairs can at once be seen and much trouble is saved. The zilladar -obtains the figures from the old field registers. The amount of detail -required as to the applicant’s lands depends on the nature of his -application. If it deals with only part of his land the other parts -should also be shown. He may for instance be giving a disproportionate -share of water to one part. If a transfer to another watercourse is -asked for, the figures for that watercourse are also required. - - -----------------+----------------------------------+--------+-------- - Areas in Acres. | Applicant’s Holding. |Total of|Total of - |-------+---------+---------+------| Water- |Distrib- - | | | |Total.| course.| utary. - -----------------+-------+---------+---------+------+--------+-------- - Culturable | | | | | | - commanded. | | | | | | - | | | | | | - Net {19...-19...| | | | | | - irri-{19...-19...| | | | | | - gated{19...-19...| | | | | | - | | | | | | - -----------------+-------+---------+---------+------+--------+-------- - | | | | | | - Total of 3 years | | | | | | - | | | | | | - -----------------+-------+---------+---------+------+--------+-------- - | | | | | | - Average | | | | | | - | | | | | | - -----------------+-------+---------+---------+------+--------+-------- - | | | | | | - Per cent. of | | | | | | - culturable | | | | | | - commanded | | | | | | - | | | | | | - -----------------+-------+---------+---------+------+--------+-------- - -If an application refers to a whole watercourse, the Subdivisional -Officer can frequently, with the aid of an irrigation register and a set -of chak maps, both kept up to date, dispose personally of the case. A -good plan is to settle cases when on tour near the place concerned, the -applicant and the zilladar being present as well as any other persons -concerned. A certain number of cases have to come up again on the -following tour, but all are settled in less time than is occupied if the -papers go up and down between the Subdivisional Officer and the -zilladar, the “file” of papers in any particular case being constantly -swollen by reminders from the applicant.[39] Moreover, the applicants -know that their views are known to the Subdivisional Officer. If the -outlets on a channel need a general remodelling, such applications as -those under consideration receive attention in connection with the -scheme. Otherwise all the applications concerning one distributary can -be considered together. If, however, a case is pressing, or the steps to -be taken obvious, it can be settled without reference to any other case. - - [39] The plan of personal settlement is distasteful not only to the - subordinates, but to the _munshi_ who has charge of the “vernacular - files.” Ordinarily he can delay a case, or manipulate it to some - extent. - -The general arrangements for the “revenue” work or assessment of water -rates have been stated in Art. 1. In the Punjab the remissions for -failed crops are a source of trouble. In some districts the failed areas -are small, and no particular trouble arises, but in other districts such -areas are often very large. On perennial canals the crop inspection is -done by the zilladars, on most of the inundation canals by the -subordinates of the District Magistrate.[40] In both cases the amount of -labour involved is enormous, and the corruption to which the system -gives rise is also enormous. In the case of the inundation canals the -superior staff of the District Magistrate nominally make checks, but the -time at their disposal is wholly inadequate. In the case of the -perennial canals the Canal Engineers are able to exercise considerable -checks, but nothing like enough. In fact the state of a crop and the -proportion of the charge on it which should be remitted is a difficult -thing to judge, even if the subordinates were without guile. It is -understood that a new and statesmanlike system is now to be introduced, -the District Magistrate deciding, in consultation with the Executive -Engineer, whether the season is such as to call for any general -remission for each kind of crop, and, if so, to what extent. The -proportion to be remitted in that crop is then to be fixed, and it is to -be the same for every one. - - [40] Officially called the “Collector” in some provinces, and “Deputy - Commissioner” in others. - -It has been mentioned that some irrigation is effected by lift. The -simplest form of lift is a horizontal pole which rests, not far from its -thick end, on a support. From its thick end is suspended a bucket, and -from its thin end a weight. A man lifts the thin end so that the bucket -then dips into the water and is filled. Pulling down the thin end he -raises the bucket and empties it. A greatly improved lifting apparatus -is the Persian wheel which is vertical and has slung from it, like the -buckets of a dredger but moving vertically, a number of earthen jars, -which scoop up the water. As each jar passes over the top of the wheel -it assumes a horizontal position, discharges its water into a shoot, and -descends in an inverted position. The wheel is moved by a simple -cog-wheel arrangement actuated by a bullock which is driven round and -round in a circular track. The Persian wheel is used for lifts of any -height. The lift from a canal watercourse is a few feet, that from a -well may be 50 feet or more. - -Most persons consider that a system of charging for water by volume -would be a very great advance on present methods. It has been said that -if the water were wasted it would be difficult for the cultivators to -bring home the responsibility to any individual. This objection does not -seem to have great force. Every individual would have a direct interest -in economising the water, and any cultivator who was habitually careless -would soon be detected by the others. In all probability the result -would be a great improvement in the duty of the water. But the justice -of any very rigid system of charging by volume is somewhat doubtful. The -great difference in the duty of water on different watercourses has been -mentioned more than once. Many of the causes of this are beyond the -control of the farmers, and it would probably be necessary to charge -reduced rates to some of them. - - - - -CHAPTER IV. - -THE PUNJAB TRIPLE CANAL PROJECT.[41] - - - [41] See Report on the Project Estimates of the Upper Jhelum, Upper - Chenab, and Lower Bari Doab Canals. - -[Illustration: FIG. 26.] - - -1. =General Description.= Fig. 26 shows part of the Punjab. The areas -marked L.J., L.C., U.B.D., and S.C. are already irrigated by the Lower -Jhelum, Lower Chenab, Upper Bari Doab[42] and Sirhind Canals. The areas -which it is considered very desirable to irrigate, and which are -provided for in the Triple Canal Project, are marked U.J., U.C., and -L.B.D., and the new canals are shown by dotted lines. Other areas -needing irrigation lie on the left bank of the lower part of the Sutlej, -partly in British territory and partly in Bahawalpur State, and one -area,[43] of scant rainfall and subject to occasional famine, lies -immediately South of the Sirhind Canal tract. There is also a very large -area between the Indus and the Jhelum, and it has been proposed to -irrigate it from the Indus, but on account of the presence of sand-hills -the project is not likely to be so useful as others, and it is held in -abeyance. Perhaps a small canal may be constructed, as a tentative -measure, to irrigate part of the tract. - - [42] Doab means “two waters,” or the tract between two rivers. The - names of the three Doabs under consideration are formed from those of - the rivers. They are called the Jech (Jhelum-Chenab), Rechna - (Ravi-Chenab), and Bari (Beas-Ravi) Doabs. - - [43] It would be very expensive to bring water for this tract from the - Beas and across the Sutlej. - -The winter discharges of the rivers (available for the rabi crop) after -the existing irrigation has been supplied, are as follows: - - Indus, 9,434 c. feet per second (minimum) - Jhelum, 6,800 „ „ (average) - Chenab, Nil - Ravi, Nil - Beas, 4,000 „ „ (minimum) - Sutlej, Nil - -In summer all the rivers have discharges (available for the kharif crop) -far exceeding any requirements. It was at one time proposed to supply -the Lower Bari Doab Canal from near the junction of the Beas and Sutlej, -and a project for this was prepared, but before it was sanctioned a -proposal was put forward to convey the surplus water of the Jhelum -eastward across the Chenab and Ravi. This valuable suggestion was made -by Sir James Wilson, who was then Settlement Commissioner of the Punjab, -and, independently, by the late Colonel S. L. Jacob, R.E., who had been -a Chief Engineer in the Punjab. The proposals were, however, to take off -the supply from the Jhelum lower down than as now arranged in the Triple -Project. This would have resulted in only a partial utilisation of the -Jhelum water, in mutilation or heavy alterations to the existing Lower -Jhelum and Lower Chenab Canals, in for ever debarring the Upper Jhelum -and Upper Chenab tracts from irrigation, and in a very costly scheme for -the Lower Bari Doab Canal.[44] - - [44] Colonel Jacob made his suggestion when in England after retiring - from India, and when he had no levels to guide him. - -The Triple Project as prepared by Sir John Benton, K.C.I.E., recently -Inspector General of Irrigation in India, gets over all the above -objections. The Upper Jhelum Canal is to irrigate the country which it -traverses, and in the winter, when the supply in the rivers is -restricted, it is to deliver into the river Chenab, above the weir at -the head of the Lower Chenab Canal, a discharge equal to that drawn out -higher up by the Upper Chenab Canal.[45] Thus the Lower Chenab Canal, -which at present draws off the whole of the water of the Chenab in -winter, will not be injuriously affected in any way. The Upper Chenab -Canal after irrigating its own tract is to deliver a large volume of -water into the Ravi. The water will be taken across that river by a -level crossing, and supply the Lower Bari Doab Canal. The water brought -into the Sutlej from the Beas will remain available for irrigation on -the left bank of the Sutlej, or possibly for the dry tract South of the -Sirhind Canal area. This fine scheme presented many difficulties and is -necessarily costly. The water has to be conveyed a great distance, and -there will be much loss by absorption. The Ravi crossing will be a very -heavy work. The Upper Jhelum Canal has to be taken by a circuitous -course round a range of hills, and to cross numerous heavy torrents. The -scheme will, however, prove remunerative in spite of immense -difficulties as to labour, caused by the outbreak of plague in the -Punjab a few years ago. - - [45] The Indus is at a higher level than the Jhelum. The latter river - runs in a comparatively deep valley, and it is unfortunately - impossible to convey the water of the Indus across this valley. - - -2. =Areas and Discharges.= The figures on which the discharges in the -Triple Project are based form a useful and interesting object lesson. In -order to obtain sufficient water in the winter, it is necessary to -reduce the rabi supply to the existing Lower Jhelum Canal. The figure -above given for the Jhelum indicates the supply available after the -reduction. More water will be supplied to the Lower Jhelum Canal for the -kharif, the canal being enlarged for this purpose, and its total -irrigation will be unaffected. The proportion of the culturable -commanded area to be irrigated in the new tracts is 75 per cent., but -from this the area irrigated by wells in the Upper Jhelum and Upper -Chenab tracts is deducted. On the Lower Bari Doab Canal there is little -well Irrigation, but there are some low-lying tracts near the rivers, -and of these only 50 per cent. will be irrigated. The kharif and rabi -areas are in all cases to be equal. - -The areas to be irrigated in each crop are as below-- - - Lower Jhelum Canal 383,091 acres - Upper Jhelum Canal 172,480 „ - Upper Chenab Canal 324,184 „ - Lower Bari Doab Canal 441,264 „ - --------- - Total 1,321,019 „ - -The total, excluding the existing Lower Jhelum Canal, is 937,928 acres. -With an equal area in the other crop, the new annual irrigation amounts -to 1,875,856 acres. - -The kharif duty is taken as 100 acres at the distributary heads, this -being about the figure actually obtained on the Lower Chenab and Upper -Bari Doab Canals, and the required kharif discharges at the distributary -heads are: - - Lower Jhelum 3,821 c. feet per second - Upper „ 1,725 „ „ - „ Chenab 3,242 „ „ - Lower Bari Doab 4,413 „ „ - ----- - Total, excluding Lower Jhelum 9,380 „ „ - -The losses of water in canal and branches have been found to be, on the -Upper Bari Doab Canal 10 c. feet per second, and on the Lower Chenab -Canal 8 c. feet per second, per million square feet of wetted area -respectively. The conditions of the latter canal most resemble those on -the new canals under consideration. The losses calculated on the wetted -areas of the channels, as designed, at 8 c. feet per second per million -square feet, are as follows, in c. feet per second: - - Lower Jhelum Canal 624} 1,288 - Upper Jhelum Canal 664} - - Upper Chenab Canal 1,161} 2,126 - Lower Bari Doab Canal 965} - ----- - Total 3,414 - -But in dry years the canals will be worked in rotation during the rabi, -the Upper Chenab and Lower Bari Doab Canals being worked together, and -the Upper Jhelum and Lower Jhelum together. - -When the Lower Jhelum Canal is closed, in course of rotation, the Upper -Jhelum Canal will still be flowing, and the loss in it, 664 c. feet per -second, has to be added to the figure (2,126) given above, thus bringing -up the loss to 2,790 c. feet per second. - -In order to ascertain what the state of affairs will be in the rabi, the -statistics obtained on the Lower Chenab Canal were examined. These show -that the rabi duty at the distributary heads on that canal is 206 acres. -On the Upper Bari Doab Canal the duty at the distributary heads is 263 -acres, but 11 per cent. of the area receives only “first waterings.” The -duty based on the remaining area is 234 acres. But the above duties are -only attained by running higher supplies in October and March than -during the intervening four months of the crop. The following remarks -and figures are taken from the Report on the Project Estimates:-- - -“The statistics of working of distributaries of the Chenab and Bari Doab -Canals give the average discharges shown in the following table for the -three years ending with 1903-04. The losses by absorption are calculated -on the wetted areas for the different rotational periods. The average -discharge less absorption is the supply which reached the heads of the -distributaries. - -CHENAB CANAL. - - ------------------+--------------------------------------------+------ - | PERIOD. | AVER- - +------+------+-----+-----+-----+-----+------+ AGE. - PARTICULARS. | Octo-| Octo-| No- | De-|Janu-| Feb-|March.| - | ber | ber | vem-| cem-|ary. | ru- | | - | 1st- | 16th-| ber | ber| | ary | | - | 15th | 31st| | | | | | - ------------------+------+------+-----+-----+-----+-----+------+------ - | Cu- | Cu- | Cu- | Cu- | Cu- | Cu- | Cu- | Cu- - | secs.| secs.|secs.|secs.|secs.|secs.| secs.| secs. - Average supply | | | | | | | | - entering head of | | | | | | | | - canal |10,196|10,285|7,788|5,593|5,127|5,500| 6,603| 6,809 - | | | | | | | | - Deduct absorption | 1,633| 1,633|1,250|1,053|1,032|1,171| 1,433| 1,262 - +------+------+-----+-----+-----+-----+------+------ - Supply at distrib-| | | | | | | | - utary heads for | | | | | | | | - 1,155,685 acres, | | | | | | | | - the average Bari | | | | | | | | - area | 8,563| 8,652|6,538|4,510|4,095|4,329| 5,170| 5,546 - +------+------+-----+-----+-----+-----+------+------ - Proportional | | | | | | | | - supply for | | | | | | | | - 1,164,595 acres | 8,631| 8,721|6,590|4,576|4,128|4,364| 5,211| 5,591 - | | | | | | | | - Add absorption for| | | | | | | | - new projects | 3,414| 3,414|2,139|2,139|2,139|2,139| 3,414| 2,564 - +------+------+-----+-----+-----+-----+------+------ - Supply required | | | | | | | | - for new projects | | | | | | | | - at heads of canals|12,045|12,035|8,729|6,715|6,267|6,503| 8,625| 8,155 - ------------------+------+------+-----+-----+-----+-----+------+------ - -“The average discharge given by the third line is 5,546, and the average -area being 1,155,685 acres, the duty at the heads of distributaries was -208. - -“The area 1,164,595 is the perennial rabi irrigation of the new -projects, the area 156,424 acres, receiving only first waterings, being -omitted to admit of a fair comparison, and is only 1 per cent. under the -average attained on the Chenab Canal in the three years for which the -table is prepared. - -“The absorption added for the two first periods is on the supposition -that all the canals are open throughout October and March, tatilling[46] -with an average absorption loss of 2,139 cusecs[47] being in force -during the other four months. The last line of the table shows the -average Rabi discharge required by the new projects at the heads of -canals, inclusive of all losses calculated on the Chenab Canal basis of -a duty of 208 acres per cusec obtained at the heads of distributaries. - - [46] “Tátíl” is the Indian word for rotational closure. - - [47] “Cusec” is used in India for c. ft. per second. - -“The Bari Doab Canal statistics furnish the means of the adequacy of -available supply being gauged. The following table furnishes particulars -for the average supply of water entering the head of the canal for the -five years 1898-99, 1899-1900, 1901-02, 1902-03, 1903-04. The figures -for the year 1900-01 are omitted, as it was a very abnormal one of very -plenteous supply and heavy rainfall:-- - -“The average irrigation for the five years in question was 442,302 -inclusive of 11 per cent. which only receives first waterings. This -divided by the average supply, 1,685, entering the head of a canal gives -a duty of 263 acres per cusec at the heads of distributaries. - -BARI DOAB CANAL. - - ------------------+--------------------------------------------+------ - | PERIOD. | AVER- - +------+------+-----+-----+-----+-----+------+ AGE. - PARTICULARS. | Octo-| Octo-| No- | De-|Janu-| Feb-|March.| - | ber | ber | vem-| cem-|ary. | ru- | | - | 1st- | 16th-| ber | ber| | ary | | - | 15th | 31st| | | | | | - ------------------+------+------+-----+-----+-----+-----+------+------ - | Cu- | Cu- | Cu- | Cu- | Cu- | Cu- | Cu- | Cu- - | secs.| secs.|secs.|secs.|secs.|secs.| secs.| secs. - Average supply | | | | | | | | - entering head of | | | | | | | | - canal | 3,769| 2,896|2,170|1,755|1,622|1,916| 2,909| 2,284 - | | | | | | | | - Deduct absorption | 599| 599| 599| 599| 599| 599| 599| 599 - ------------------+------+------+-----+-----+-----+-----+------+------ - Supply at heads of| | | | | | | | - distributaries | | | | | | | | - (_a_) | 3,170| 2,297|1,571|1,156|1,023|1,317| 2,310| 1,685 - ------------------+------+------+-----+-----+-----+-----+------+------ - Corresponding | | | | | | | | - supply for new | | | | | | | | - schemes 3 × | | | | | | | | - figures line (_a_)| 9,510| 6,891|4,713|3,468|3,069|3,951| 6,930| 5,055 - | | | | | | | | - Add absorption for| | | | | | | | - new projects | 3,414| 3,414|2,139|2,139|2,139|2,139| 3,414| 2,564 - ------------------+------+------+-----+-----+-----+-----+------+------ - Supply required | | | | | | | | - for new projects | | | | | | | | - at heads of canals|12,924|10,305|6,852|5,607|5,208|6,090|10,344| 7,619 - ------------------+------+------+-----+-----+-----+-----+------+------ - -“The rabi irrigation of the new projects is 1,321,019 acres,[48] and -this divided by 442,302 gives approximately the multiplier 3 referred to -at (_a_) in the above table. - - [48] Including the Lower Jhelum. - -“The figures given in the above table and in the foregoing remarks -relate to the aggregate of the areas in the rabi which receives a -perennial supply and which only receives first and last waterings. On -the Upper Bari Doab Canal the rabi which receives perennial irrigation -is averagely 393,649 acres; the average supply of 1,685 cusecs gives on -this area a duty of 234 acres per cusec at the heads of the -distributaries. - -“In the case of the three projects the aggregate _rabi_ area receiving -perennial irrigation as shown by the table, paragraph 21[49] _supra_, is -1,164,595 acres: this is 2·96 times 393,649; so that the proportional -supply required on this basis would be slightly less than that given by -the multiplier 3 in the above table. - - [49] Not printed. The area is the total rabi area less the area which - is to receive only first waterings. - -In explanation of the difference of the duties:-- - - Lower Chenab Canal 208 acres per cusec, - Upper Bari Doab Canal 234 ditto, - -it may be stated that the Lower Chenab Canal is a comparatively new -work, and that the duty has been steadily rising and, with the perfect -watercourse system, may be relied on to reach the Upper Bari Doab Canal -234 acres per cusec in the course of time for water arriving at the -heads of distributaries. - - * * * * * - -“27. =Summary of conclusions as to sufficiency of supply.=--The -following table shows all the foregoing results in a form readily -admitting of comparison:-- - - ----------+----------------------------------------------------------+ - PARTIC- | PERIOD. | - ULARS. +---------+--------+-------+-----+------+---------+--------+ - | 1st to | 6th to | Novem-| De- | Janu-| Febru- | March. | - | 15th | 31st | ber. | cem-| ary.| ary. | | - | October.|October.| | ber.| | | | - | | | | | | | | - ----------+---------+--------+-------+-----+------+---------+--------+ - | Cusecs. | Cusecs.|Cusecs.| Cu- | Cu- | Cusecs. | Cusecs.| - | | | |secs.| secs.| | | - AVERAGE | | | | | | | | - SUPPLIES | | | | | | | | - AVAILABLE.| | | | | | | | - | | | | | | | | - Very fa- | | | | | | | | - vourable |{ 21,400 | 15,150 |}11,850|8,626|11,200|{ 13,100 | 21,250 | - years 1 |{(13.063)|(13,063)|} | | |{(13,063)|(13,063)| - in 4 | | | | | | | | - | | | | | | | | - Ordinary |{ 13,900}| 11,850 | 10,000|7,400| 7,600| 9,100 |{16,500 | - years 2 |{ 13,063}| | | | | |{13,063 | - in 4 | | | | | | | | - | | | | | | | | - Dry years | 10,150 | 9,100 | 7,275 |5,950| 5,610| 6,100 | 11,345 | - 1 in 4 | | | | | | | | - | | | | | | | | - Minimum of| 9,710 | 8,003 | 6,624 |5,810| 5,563| 5,163 | 9,791 | - 14 years | | | | | | | | - +---------+--------+-------+-----+------+---------+--------+ - Require- | | | | | | | | - ments on | | | | | | | | - average of| | | | | | | | - Lower | 12,045 | 12,135 | 8,729 |6,715| 6,267| 6,503 | 8,625 | - Chenab | | | | | | | | - Canal for | | | | | | | | - 3 years | | | | | | | | - | | | | | | | | - Require- | | | | | | | | - ments on | | | | | | | | - average of| | | | | | | | - Upper Bari| 12,924 | 10,305 | 6,852 |5,607| 5,208| 6,090 | 10,344 | - Doab Canal| | | | | | | | - for 5 | | | | | | | | - years | | | | | | | | - ----------+---------+--------+-------+-----+------+---------+--------+ - - ----------+-------+-------+---------+-----------+----------- - PARTIC- |Average|Deduct |Supply at|Duty calcu-|Duty calcu- - ULARS. +supply |loss by|heads of | lated on | lated on - | in |absorp-|distribu-|1,321,019 |1,164,595 - | river.| tion. | taries. |acres, the |acres, the - | | | |gross rabi | perennial - | | | | area. | area. - ----------+-------+-------+---------+-----------+----------- - |Cusecs.|Cusecs.| Cusecs. | | - | | | | | - AVERAGE | | | | | - SUPPLIES | | | | | - AVAILABLE.| | | | | - | | | | | - Very fa- | | | | | - vourable |}11,811| 3,414 | 8,397 | 158 | 139 - years 1 |} | | | | - in 4 | | | | | - | | | | | - Ordinary |} 9,946| 2,989 | 6,957 | 189 | 167 - years 2 |} | | | | - in 4 | | | | | - | | | | | - Dry years | 7,651| 2,564 | 5,087 | 259 | 229 - 1 in 4 | | | | | - | | | | | - Minimum of| 6,968| 2,458 | 4,510 | 293 | 258 - 14 years | | | | | - +-------+-------+---------+-----------+----------- - Require- | | | | | - ments on | | | | | - average of| | | | | - Lower | 8,155| 2,564 | 5,591 | 236 | 208 - Chenab | | | | | - Canal for | | | | | - 3 years | | | | | - | | | | | - Require- | | | | | - ments on | | | | | - average of| | | | | - Upper Bari| 7,619| 2,564 | 5,055 | 261 | 230 - Doab Canal| | | | | - for 5 | | | | | - years | | | | | - ----------+-------+-------+---------+-----------+----------- - -“The 13,063 shown in brackets represents the parts of the available -supply which the canals can carry, the capacity being as follows:-- - - Cusecs. - Lower Jhelum Canal 4,563 - Upper Jhelum Canal 8,500 - ------ - Total 13,063 - ------ - -“The average supplies and duty figures are based on the 13,063 cusec -maximum capacity and not on the larger available supplies written above -these figures where they occur. - -“The above table goes to show the following: - - (_i_) In order to utilize the large supplies available in the Jhelum - River in October and March every year and in some or all of the - intervening months in other years, it is advisable to give the Upper - Jhelum Canal the large capacity of 8,500 cusecs proposed. - - (_ii_) In favourable and ordinary years, that is, in 3 out of 4, the - available supply will be ample, as shown by the low duties of 189 and - 167 compared with those obtaining on the Lower Chenab and Upper Bari - Doab Canals. - - (_iii_) In dry years, that is, 1 in 4, it will be necessary to attain - a duty almost exactly the same as that now obtaining on the Upper Bari - Doab Canal. - - (_iv_) That an exceptionally dry year might occur once in 14 years, - when the supply would be 10 per cent. short of that required by the - average Upper Bari Doab Canal standard of requirements: such - exceptional cases should be met by remissions, which will be far - preferable to wasting the good supplies of 13 years out of 14. - - (_v_) That the occasional occurrence of dry years makes it inadvisable - to attempt a greater proportion of rabi than half of the annual - irrigation.” - - -3. =Remarks.= The Report on the Project estimates gives, for each tract, -remarks on its soil, rainfall, height of subsoil water, circumstances as -to existing irrigation from wells or small canals and liability to -floods. On a consideration of these matters the decision as to the -particular parts of the tracts which are to be irrigated and the areas -which are, in the rabi, to receive only restricted irrigation, -depends.[50] - - [50] It is not unusual, in tracts where the level of the subsoil water - is high, say within 15 feet of the surface, to have some “kharif - distributaries.” These are closed in the rabi. This tends to prevent - water-logging of the soil. In the rabi the people lift water from - wells. There may also be kharif distributaries in dry tracts if there - is no water to spare in the rabi. - -In calculating the sizes of the canals, N in Kutter’s co-efficient was -taken at ·020. In sharp curves the bed is paved on the side next the -concave bank. In high embankments where the soil is sandy the best -material is used as a core wall. The torrent works on the Upper Jhelum -Canal have been mentioned in _River and Canal Engineering_, Chapter XII. - -Regarding the effect of the new canals on the inundation canals which -take off, lower down, from the Chenab below its confluence with the -Jhelum, it has for long been the policy to gradually shift the heads of -these canals upstream in order to obtain better supplies, or rather to -counteract the effect of the abstraction of water for the recently -constructed Lower Chenab and Lower Jhelum Canals. Any such abstraction -of water has not much effect on the floods, but it has much effect in -April and May, when the rivers have not fully risen, and in September, -when they are falling. - -In order to estimate the effect on the water level of the Chenab--below -its junction with the Jhelum--it was necessary to observe discharges of -the river, not only in the winter when it is low, but in the summer when -it is high. The depth of the water was in some places 40 feet, and the -stream 2,000 feet wide. Fortunately the Subdivisional Officer was a -native of India and did not much mind the sun. A discharge curve (_River -and Canal Engineering_, Chapter III. Art. 5,) having been prepared, it -was possible to construct a diagram with periods of time as the -abscissas, the ordinates representing the average known gauge readings -on the different dates and another set of ordinates representing the -probable discharges. By deducting the discharges which it was intended -that the new perennial canals should draw off, it was possible to draw -fresh ordinates representing the diminished river discharges and the -reduced river gauge readings corresponding to them. It was found that -the water level would be lowered by about 1·3 feet in April and May, and -by about 1·5 feet in September. It was, however, shown that by shifting -the heads of the inundation canals upstream--the gradients of the canals -being flatter than that of the river--the effect of the lowering of the -water level could, as heretofore, be nullified. - - - - -CHAPTER V. - -PROPOSED IMPROVEMENTS IN IRRIGATION CANALS. - - -1. =Preliminary Remarks.=--The chief improvements which have been under -consideration during recent years are three in number. The first is -increased economy of water in its actual use in the fields; the second -is reduction of the losses by absorption in the channels; and the third -is distribution by means of modules. - -Regarding the first, it has long been known that the ordinary methods of -laying on the water are more or less wasteful. In California, when the -water instead of being applied to the surface of the ground, is brought -in a pipe and delivered below the ground level, the duty is increased -from 250 to 500 acres. In India a field is divided, by means of small -ridges of earth, into large compartments. The water is let into a -compartment and gradually covers it. By the time the further side is -soaked the nearer side has received far too much water. Frequently the -water for a compartment, instead of being carried up to it by a small -watercourse, is passed through another compartment and this adds to the -waste. Also the number of waterings given to a crop is often 5 or 6, -when 4 would suffice. Experiments made on the Upper Bari Doab Canal, by -Kennedy, showed that the water used in the fields was nearly double what -it might have been. The 53 c. ft. shown in Chapter 1, Art. 4, as -reaching the fields, were used up when 28 c. ft. would have sufficed. It -is not certain that the waste is generally quite as much as the above. -It is possible that the restricted supplies might have given smaller -yields of crops. More recent experiments made by Kanthack on the same -canal give the needless waste as about 25 per cent. The field -compartments ought, according to Kennedy, to be 70ft. square, the small -branch watercourses being 140ft. apart. It would be better to have still -smaller compartments, but this would be rather hard on the people. - -At one time Government issued orders, in Northern India, that -compartments of 1296 square feet were to be used, and that, otherwise, -increased water rates would be charged, but the orders were never -enforced. They were thought to press too hardly on the people. Extreme -measures for enforcing economy in the use of water in any country are -likely to be introduced only when they become absolutely necessary owing -to the supplies of water being otherwise insufficient. - - -2. =Reduction of Losses in the Channels.=--For several years experiments -have been going on in the Punjab as to the effect of lining watercourses -with various materials. The following conclusions have been arrived -at[51]:-- - - [51] _Punjab Irrigation Paper_ No. 11 C. “Lining of Watercourses to - reduce absorption losses. Experiments of 1908-1911.” - - -I. ORDINARY UNLINED TRENCHES. - - (_a_) The rate of absorption varies greatly, and this is due probably - to unequal fissuring of the upper layers of the soil. - - (_b_) The rate of absorption in the three hottest months averaged - ·0571 feet per hour, or more than double the rate (·026) in the three - coldest months. The difference is ascribed to the greater viscosity - of the water when cold. - - (_c_) The average losses with canal water were ·0315 feet per hour, or - 8·75 c. feet per second per million sq. feet.[52] With well water the - figures were ·1096 and 30·5. The conclusion is that the silt in canal - water reduces the losses by more than two-thirds. - - [52] This loss of 8·75 c. ft. per second was in water only about a - foot deep. This confirms the conclusion arrived at in Chapter I, Art. - 4, that the depth of water is not a factor of much importance. - - (_d_) With canal water the average loss decreased by 40 per cent. - (from ·0491 to ·0293) in about four years. This was no doubt due to - the effect of the silt. With well water the loss at the end of four - years (·2293) was nearly four times as great as at first (·0591). This - may have been due to removal of the finer particles of soil by the - water, but the experiments were made at only one place, and were not - conclusive. - - -II. LINED TRENCHES. - - (_e_) With trenches lined with crude oil ¹⁄₁₆ inch thick, or with - Portland cement ¹⁄₁₆ inch thick, or with clay puddle 6 inches thick, - the “efficiency ratios,” as compared with unlined trenches, are - respectively about 4·0, 5·7 and 5·7, the age of the lining being four - years. The efficiency ratio is the inverse of the loss. Thus with an - efficiency ratio of 3 the loss in the lined trench is 33 per cent. of - that in the unlined trench. - - (_f_) The efficiency ratio in the case of oil may diminish at the rate - of 10 per cent. per annum, but in the case of cement and clay puddle - it tends to increase rather than to decrease. - -Assuming that the efficiency ratios are only 3·0, 4·5 and 4·5, and that -the loss in an unlined channel is 8 c. feet per second per million sq. -feet, the saving in water by using channels lined with oil, cement and -puddle respectively would be 5·33, 6·25 and 6·25 c. feet per second. The -average duty of the water at the canal head is about 242 acres, and the -average revenue per acre is Rs 3·93. The revenue from 1 c. ft. of water -at the canal head is thus Rs 950. Only about half the water reaches the -fields (Chapter I., Art. 4), and the revenue from 1 c. ft. of water -which reaches the fields is about Rs 1900. The mean of the above two -sums is Rs 1425. If 6 c. ft. of water per second could be saved the -revenue would be increased by Rs 8,550 per annum. - -The cost of lining a million square feet of channel with oil, cement and -puddle is estimated at Rs 30,000, Rs 27,500 and Rs 35,000 respectively. -Allowance has to be made for the fact that watercourses flow -intermittently, and that a lined channel gives no saving when it is not -in flow, also that extensions of canals might have to be undertaken in -order to utilise the water saved. After making these allowances it is -estimated, in the paper above quoted, that the saving effected by lining -a million square feet with oil, cement or puddle represents the interest -on a capital sum of Rs 69,300, Rs 81,250 and Rs 81,250 respectively, or -2 or 3 times the sums sunk in constructing the linings. - -Hitherto the experiments have been carried out on a moderate scale, but -extensive operations are now being undertaken on the Lower Chenab -Canal, and possibly on others. - -In cases where it is not desired to incur much expenditure, it may be a -good plan to construct watercourses to a cross section somewhat larger -than that ultimately desired. The silt deposited on the bed and sides -forms, in most cases, a more impervious lining than the original soil. -The same plan can be adopted in the tail portion of a distributary. In a -larger channel there would be less certainty that any deposit would take -place unless short lengths, at frequent intervals, were excavated to the -true or ultimate section, so as to form weirs and spurs; and even these -might not stand. - -In Italy, in cases where the water naturally contains lime in -suspension, the beds of canals have become gradually watertight by the -deposit of lime in the channel.[53] In some cases lime has been -artificially added. It appears that a considerable period of time is -necessary for the process. - - [53] Min. Proc. Inst. C. E. Vol. CXVI. - - -3. =Modules.=--A module is an appliance which automatically gives a -constant discharge through an aperture, however the water level on -either the upstream or downstream side of the aperture may fluctuate. In -an old and simple form of module there is a horizontal orifice in which -works loosely a tapering rod attached to a float. The water passes -through the annular space surrounding the rod. If the water level rises, -the rise of the float brings a thicker part of the rod to the orifice -and reduces the annular space. In another kind of module the water is -discharged through a syphon. If the water level alters, the syphon moves -in such a way that the head, or difference between the levels of its -two ends, remains the same. The great objections to modules are that -they are liable to get out of order or to be tampered with. A module -recently invented and patented by Gibb[54] has no movable parts, and is -not liable to these objections. - - [54] For description see Appendix H. - -A few years ago the question of the desirability of using modules for -the outlets of distributaries in India was raised. The opinions of a -large number of the senior canal engineers were called for and -considered, and since then the subject has been thoroughly discussed. -There are certain inherent difficulties in the way of moduling the -outlets of a distributary. Owing, for instance, to rain further up the -canal, or to the closure of a distributary owing to a breach in it, the -canal supply may increase, and it may be necessary to let more water -into the distributary under consideration. Under the present system any -excesses of water are automatically taken by the outlets. If all outlets -were rigidly moduled they would discharge no more than before the excess -supply came in, and the excess supply would all go to the tail of the -distributary, and, most likely, breach the banks. To get over this -difficulty, the module has to be so arranged that when the water level -in the distributary rises to a certain “maximum limit” the module ceases -to act as such, and the discharge drawn off from the distributary -increases as the water level rises. Again, the discharge of the -distributary may at times be considerably less than its full supply. In -order that, in such a case, the outlets towards the tail of the -distributary may not be wholly deprived of water, it has to be arranged -so that when the water level in the distributary falls below a certain -“minimum limit” the modules cease to act as such, and draw off supplies -which are less the lower the water level. Such supplies are not in -proportion to the full supplies of the outlets. It will, however, be -shown presently that low supplies need seldom be run. When a -distributary, say the upper reach, contains silt, the water level -corresponding to a given discharge is higher than before, and care has -to be taken that the maximum limit is high enough. At the same time the -minimum limit must be so low that it will not be passed when the silt -scours out. The difference between the maximum and minimum limits is -called the “range” of the module. - -In Gibb’s module the above conditions can be complied with. The module -is placed outside the bank of the distributary. The water is drawn off -from the distributary by a pipe, whose lower edge is at the bed level of -the distributary, and delivered from the module into the watercourse -through a rectangular aperture at a higher level than that of the pipe. -It is possible that, owing to the high level of the aperture, some -rolling silt which would otherwise have passed out of the distributary -may remain in it. The height of the aperture also prevents the -watercourse from drawing off any water at all when the water level of -the distributary falls below a certain level, but this objection is not -important. An escape weir or notch is provided so that when the water -level in the distributary rises to the maximum limit some water -overflows into the watercourse. On the whole it appears that all -difficulties can be got over, though a good deal of care and precision -is necessary in fixing the exact height of the maximum and minimum -limits. - -The difficulties under consideration will all be reduced if some of the -outlets on a distributary are left unmoduled, and this is desirable on -other grounds. When the supply is normal, _i.e._ between the maximum and -minimum limits, and all modules are working, the supply entering the -distributary must be regulated with great precision. The outlets draw -off a certain supply. If less than this enters the distributary the tail -outlets must go short. If more enters there will be a surplus at the -tail, though it can probably be disposed of, because the tail water will -rise above the maximum limit. For short periods, say an hour or two, no -trouble arises because the distributary acts as a reservoir, the water -level rising to take in any excess supply, and falling to allow for a -deficiency. At the tail the rise and fall may be hardly perceptible. But -if the supply were deficient for a whole night the tail outlets would -certainly go short. This could theoretically be remedied to some extent -by letting in an excess supply for a short time and causing the water -level at the tail to rise above the maximum limit, but in practice no -such system of compensation could be worked. The very fact of the tail -outlets having gone short for a night would not be known. The proper -method of preventing any such troubles as those under consideration is -to leave some of the outlets on the distributary un-moduled. - -It has been more than once mentioned that there are periods when a -distributary is run, not full, but about three-fourths full. If that -were done in the case of a distributary whose outlets were mostly -moduled, the water level would probably be below the minimum limit, and -the modules would not be acting as such. The outlets would not, under -these circumstances, obtain their proper proportionate supplies. This -difficulty can, no doubt, be got over by running the distributary full -for short periods at a time instead of three-fourths full for longer -periods. The people, when once they understood the case, could arrange -to use the water in greater volume for two days instead of in smaller -volume for three. If this arrangement comes into force it will not be -necessary to design distributaries--see Chapter III, Art. 4--so as to -have a good command when three-fourths full supply is run. - -On nearly every distributary there are some watercourses whose command -is bad, and it has been stated (Chapter II, Art. 9) that in an ordinary -unmoduled distributary the sizes of the outlets in such cases should be -extremely liberal. To module any such outlet would cause a lowering of -the water level in the watercourse and would interfere with the -irrigation. Such outlets should not be moduled. Again, there are some -few outlets which are not submerged, _i.e._, there is a free fall into -the watercourse. The discharge does not depend on the water level in the -watercourse, and it is not affected by any enlargement or clearance of -it. It depends only on the water level in the distributary. This water -level, if most of the outlets are moduled, will be fairly constant. Such -outlets need not be moduled, and they should not be moduled unless the -other unmoduled outlets in the reach concerned are sufficiently -numerous, and perhaps not even then, because moduling involves some -expense. - -A distributary generally has some falls which divide it into reaches. -Immediately upstream of a fall the water level for a given discharge is -not affected by the silting or scouring of the channel. Any outlets near -to and upstream of the fall are less subject than others to variation in -discharge, and are suitable for non-moduling in case a sufficient number -of unmoduled outlets is not otherwise obtainable. - -Regarding the watercourses at the extreme tail of a distributary it has -been pointed out (Chapter III., Art. 7) that in an ordinary case they -should not be left without masonry outlets, because they may then lower -the water level and so unfairly reduce the supply of any watercourse, -even though upstream of them, which has such an outlet. But any outlets -near the tail of a distributary can suitably be left unmoduled because -of the difficulty of ensuring that the supply at the tail shall be -exactly what is needed. - -Gibb’s modules have been tried on various distributaries in the Punjab -and found to give good results. It is believed however that in only one -case has a whole distributary been moduled. The distributary is a large -one, its length being 35 miles. It appears that the discharge reaching -the tail of the distributary is not constant but varies, as was to be -expected, when the head discharge varies for any length of time. The -command on the distributary is good. There is nothing to show that -matters would not have been improved, and money saved, by leaving some -of the outlets without modules. - -It has been remarked above, that at the downstream end of a reach ending -in a fall, the F.S. level of a distributary is not affected by silt. At -the upstream end of the reach it is affected. There are thus two -gradients, one flat, and one steep. It appears to have been decided in -one case in the Punjab, that the minimum limit of supply for the module -should be about half an inch below the flat line and the maximum limit -·3 feet above the steep line. In many cases a greater range would be -required,[55] say a foot. - - [55] It is understood that a range of a foot can easily be arranged - for, and that ranges of 3 or 4 feet can be introduced at slightly - increased cost. - -In Chapter III. Art. 7, the case of a distributary without modules but -with the outlets carefully adjusted, was considered. The question to be -decided in each case is whether such an arrangement is preferable to -moduling some of the outlets. This turns largely on the amount of -attention which would be bestowed on the case. In view of the difficulty -of securing such attention and of the trouble of constantly making -alterations in a certain number of outlets, it is probable that moduling -will in many cases be considered preferable. - -The question of moduling the heads of distributaries has also been -considered in the Punjab. For minor or small distributaries modules are -feasible. For a large distributary a module would be expensive and it -appears that the present system of regulating is preferable. - -Kennedy’s “Gauge Outlet,” which is a kind of semi-module is described in -Appendix K. It is being tried in the Punjab. - - - - -APPENDICES. - - -APPENDIX A. - -DIVIDE WALL ON LOWER CHENAB CANAL. - -(See page 50, first footnote.) - -[Illustration: FIG. 27.] - -The Gagera branch of the Lower Chenab Canal--the left-hand branch in -fig. 27--was found to silt. It was proposed to make a divide wall (fig. -27) extending up to full supply level. The idea is unintelligible. The -silt does not travel by itself but is carried or rolled by the water. As -long as water entered the Gagera branch, silt would go with it. The -authorities, who had apparently accepted the proposal, altered the -estimate when they received it, and ordered the wall to be made as shown -dotted and of only half the height. This was done. The idea seems to -have been that the wall would act as a sill and stop rolling silt. This -is intelligible, but such sills do not always have much effect on -rolling silt. Moreover, there was a large gap, A B, in the wall. The -work is said to have proved useless, and proposals have been made to -continue the wall from A to B. In this form it is conceivable that it -may be of use. - - -APPENDIX B. - -SPECIFICATION FOR MAINTENANCE OF CHANNELS. - -(See page 138.) - - -I. ROADS AND BANKS. - - -1. =Filling Holes.=--Holes to be all dug out and thoroughly opened and -inspected, then to be filled in with rammed earth. Never to be filled in -a hurry or without digging out. - - -2. =Dressing.=--Heavy soil to be dressed even. Light sandy soil to be -disturbed as little as possible, and grass in such soil not to be -removed except when in large tufts. When dressing is done, the road to -be given (as far as possible) a transverse slope from the canal side of -about 1 in 50. - - -3. =Trees.=--Branches to be lopped so as not to obstruct riders. Great -care is needed to see that the men do not lop needlessly high. Roots, if -projecting on road, to be covered up or cut out. - - -4. =Petty Repairs.=--Settlement or wearing down, if slight, should be -made good on maintenance estimates, otherwise on special estimates. -Cracks should be dug out and filled in and rammed. Old “dead men” or -walls of earth should be utilised or at least levelled down. - - -5. =Sand or “Reh” Soil.=--Can be dug out to a depth of 9 inches and -removed to a distance, and (the places having been inspected by the -Subdivisional Officer) replaced by good soil got from pits or berms, the -places being selected with care. If the lead is slightly askew, the -stuff removed can be put in the same pits from which earth is got. - - -6. =Laying long coarse Grass on Road.=--This can be done in cases where -the removal of sand or “reh” is not practicable or has proved -ineffective. The grass is laid crosswise to prevent wheels sinking in. - - -II. JUNGLE AND TREES. - - -1. =Jungle.=--To be cut close to the ground or to be dug out by the -roots when ordered. To be burned as soon as dry. Dead branches, twigs, -etc., to be burned or removed to rest-houses, and not left about on -canal land. Precautions to be taken against damage by fire to forests, -etc. Clearance to include the channel[56] and both roads, and any jungle -on the slopes of the spoil which obstructs the roads.[57] - - [56] Jungle on inside slopes not to be cleared where banks fall in or - where channel is too wide. - - [57] When an embankment runs parallel to an inundation canal, a chain - or so distant, the intervening space need not be cleared, nor need the - top of a bank be cleared if it is so uneven that it is not a road. - - -2. =Trees.=--Trees which fall into a channel or across a road to have -their branches cut away at once. The trunk to be removed so far as is -possible. Trees which are dead or broken off should be felled, also -those which have been blown into inclined positions, unless bad gaps -will be caused. Trees (unless required for stock) to be sold as they lie -and removed, including the parts below ground, by purchasers, within a -fixed time. Logs, etc., not to be left lying about on canal land. -Stumps, etc., to be made into charcoal and the holes filled up. - -_Note._--The above works (Parts I. and II.) to be done immediately after -the rains (repairs to roads and removal of trees, branches, etc., being -also done during the rains or whenever necessary) and finished at latest -by 31st October. - - -III. CATTLE CROSSINGS OR GHÁTS. - - -1. =Repairs.=--Gháts to be dressed, strengthened, and kept neat, the -bank being thrown back and curved so as to give a long inner slope, and -lumps, etc., levelled off. - - -2. =Closures.=--To be closed (by order of Subdivisional Officer and no -one of lower rank) only when very near to a bridge or near to another -ghát.[58] If closed, to be staked up and bushing to be added. Not to be -closed by loose thorny branches. Not to be allowed close to any -milestone, outlet, etc. - - [58] Regarding gháts at bridges, see Chap. II., Art. 12. - - -3. =Small Gháts.=--Gháts where only foot-passengers cross, can run -diagonally up the slopes or as may be convenient. They should be dressed -and kept in order. - - -4. =Canal Road at Gháts.=--At all gháts care must be taken that the -canal road, especially if used for driving, is not cut up and is kept in -proper order. - - -IV. MISCELLANEOUS ITEMS. - - -1. =Rubbish or Obstructions in Bed of Channel.=--To be removed from the -channel when it is laid dry, and not left till it is about to be -reopened.[59] Old stakes, etc., to be sawn off when crooked or too high. - - [59] Where the bed is too low, no rubbish clearance should be done - except in the case of very large snags, etc. - - -2. =Temporary Aqueducts or Damaged Wooden Bridges.=[60]--To be removed -before water is expected (but not sooner than is necessary) and the -banks repaired and made good. - - [60] This applies to inundation canals. - - -APPENDIX C. - -SPECIFICATION FOR MAINTENANCE OF MASONRY WORKS. - -(See page 138.) - - -1. =General Repairs.=--Masonry, plaster, pitching, etc., to be kept in -repair. Pitching, where defective or out of line, to be made right. -Bumping posts to be fixed in proper positions. Earth to be added to -ramps, etc., where needed. Metalling to be regularly seen to. Needles, -planks, hooks, railings, winches, lamp-posts, lamps, etc., to be kept in -order and complete. Bricks, bats, etc., to be properly stacked. Needles, -etc., to be neatly stacked on rests or with bricks under them. All -surplus and useless needles, etc., to be removed. Huts to be kept in -repair. Extra mud walls or screens not to be allowed when unsightly. All -verandah openings to be edged with a 6-inch band of whitewash. - - -2. =Jungle.=--All masonry to be kept free from jungle growth, and all -piers free from caught jungle. For this purpose long bamboo weed-hooks -to be supplied. - - -3. =Dressing, etc.=--Rubbish, lumps of earth, logs, etc., to be cleared -away, pits and holes filled up. Banks, slopes, etc., of main and branch -channels in the neighbourhood of the work to be specially levelled and -dressed. - -_Note._--All works should be specially seen to in October, and -everything be in order by 31st October. - - -APPENDIX D. - -WATCHING AND PROTECTING BANKS AND EMBANKMENTS.[61] - -(See page 138.) - - [61] This is reprinted from _Punjab Rivers and Works_. It was drawn up - for inundation canals and flood embankments. - - -1. =Watching.=--Every watchman employed to have a fixed headquarters and -a fixed beat. If there is no permanent hut on or near the bank, grass -huts should be erected by the men at the places fixed. The presence or -absence of the men to be frequently tested by the mate and suboverseer. -The suboverseers tests to be recorded in a book and to form the subject -of frequent inquiry by the Subdivisional Officer, who will also record -his remarks and take proper action in case the suboverseer is in fault. - - -2. =Gauge Readers, Regulating Establishment, Bungalow Watchmen, -etc.=--To be made to assist whenever possible. The allotment of a beat -to each such man has been separately ordered. - - -3. =Employment of Men on Repairs.=--The men, when not otherwise -occupied, to do petty repairs, etc., within their beats, but not to be -put on miscellaneous duties and sent about as messengers, nor to act as -orderlies or khalassies. - - -4. =Strength of Establishment.=--Should generally be greater for one -and a half months in July and August than at other times. Care to be -taken as to this and as to dismissing men when no longer needed. - - -5. =Stakes and Mallets.=--To be collected beforehand, if necessary, at -suitable places, to be accounted for at end of flow season and balance -taken care of. - - -6. =Breaches.=--The Establishment to be trained by the Subdivisional -Officer to report every breach to all officials with the greatest -possible speed. The mate, daroga, and suboverseer to remain there till -the breach is closed and to promptly send a report on the prescribed -form to the Subdivisional Officer. - - -7. =Serious Breaches.=--In case of serious breaches of main channels the -Subdivisional Officer to himself reach the spot as soon as possible. - - -8. =Breach Reports.=--See printed form M[62] attached. To be promptly -submitted for each breach to the Executive Engineer. The report contains -a column for cost of closure. This means the stoppage of the flow and -not the complete making up of the banks. The column for remarks of the -Executive Engineer should be filled in and the report promptly returned -to the Subdivisional Officer, who will, in the meantime, be making up -the banks and preparing a requisition or estimate. - - [62] Not printed. - - -9. =Progress Report.=--With the Executive Engineer’s monthly progress -report a list of breaches will be submitted, canal by canal, with -columns showing date of occurrence and cost of closure. The return -should be on the attached form G.[63] The Subdivisional Officer should -also submit this form to the Executive Engineer. - - [63] Not printed. The form differs slightly from a form prescribed by - the Chief Engineer for general use in the Province. - - -10. =Estimates.=--The cost of breaches is not to be charged to -maintenance estimates. At the close of each month the Executive Engineer -should submit or sanction an estimate, accompanied by the breach -reports, for closing any breaches which have occurred and making up the -banks. - - -11. =Breaches in the Flooded Area near Canal Heads.=--These may be of -special importance. It may be impossible to do any good and money may be -uselessly spent. In any such cases the Subdivisional Officer should at -once proceed to the spot and the case should be reported by wire to the -Executive Engineer and, if necessary, to the Superintending Engineer. - - -12. =Breaches in Flood Embankments.=--The Subdivisional Officer must at -once proceed to the spot and the case be reported by wire to the -Executive Engineer and Superintending Engineer. The Breach Report forms -can be submitted partially filled in at the earliest possible moment and -a complete form afterwards. - - -APPENDIX E. - -SPECIFICATION FOR BUSHING. - -(See page 139.) - -1. The object of bushing is to form a silt berm and thus prevent or stop -the falling in of the banks. - -2. The branches must be thickly packed in order that the water among -them may become still, and also in order that they may not be shifted by -the stream. If thickly packed, the pegs required will also be fewer. -Most of the branches should be leafy and freshly cut, but, mixed with -these, there may be a proportion of kikar or other leafless branches. -Frequently it is possible to utilise jungle trees of small value, -bushes, scrub jungle, or even long grass. - -3. Except when the bushes are to be very small or the length to be -bushed very short, the proposed line for the edge of the berm should be -marked out by long stakes driven in the water at fairly close intervals. -Otherwise the work may be badly done and the berm formed imperfect and -out of line. - -4. As the berm formed is not likely in any case to be perfectly -straight, and as subsequent additions to it will be difficult, while -trimming it will be easy, the bushes should extend slightly beyond the -line of the proposed berm. Care should be taken that the lower branches, -which cannot be seen when once submerged, are long enough. - -5. The branches should be piled up to above water-level, so that, as -they settle, they will assume the position desired, but to lay them high -above full-supply level on the slopes is useless and wasteful. If the -pegs have to be driven at a high level, the branches should be attached -to them by thin ropes or twine. Long pegs standing up high above the -ground are also wasteful. The pegs should as far as possible be kept in -line and their heads at one level. - -6. If bushing is begun during low supply, it need not, at first, extend -up to full-supply level. More branches, freshly cut, can be added as the -supply rises. In any case it is generally necessary to make some -additions to bushing from time to time, and this should be explained to -contractors and others when fixing the rates. - -7. If the trees from which branches are cut are in desirable places, the -branches should be cut with judgment; but where trees are in places -where they should not be (_e.g._, on the inside slopes of the channels), -all the branches may be cut off. The trunk may be left temporarily in -order to supply more branches. - - -APPENDIX F. - -ESCAPES. - -(See page 9.) - -There are no definite rules regarding the capacity of the escapes to be -provided on a canal. On some canals in dry tracts of country the -discharging power of the escapes is a mere fraction of that of the -canal. In other cases it is about half that of the canal. In a district -liable to heavy rain an escape, say at a point where a canal divides -into branches, should be able to discharge about half of the main canal -supply. On branches, escapes, if provided at all, usually discharge into -reservoirs, and their period of working is very limited: it may be only -twenty-four hours. - -On distributaries, escapes are seldom provided. It has been suggested, -in connection with modules, that the people irrigating from each -watercourse should be responsible for disposing, by means of it, of a -certain quantity of surplus water. This would be too rigid a rule. On -some watercourses there is much waste land or land under rice -cultivation; in such cases surplus water can be passed off without -damage. The canal subordinates are fully cognisant of such cases, and -they arrange accordingly. In other cases surplus water would do some -damage; but on nearly every distributary the full supply, even when -there is no demand for water, can be got rid of for a few hours, or even -more, without a breach occurring. - -Escapes at outlets, in connection with modules, can be arranged by means -of waste weirs or by means of Gregotti’s syphons (_sifoni -autolivelatori_). The following is an abridged translation of part of a -pamphlet by Gregotti:-- - - The figure represents one of the syphons installed in the “Centrali - Milani.” - - A is the supply basin of the “Centrali,” which ends in the syphon B. - The latter is constructed with mouthpiece of rectangular section _a_, - which is submerged in the basin A. A weir divides the mouthpiece of - the syphon from the descending branch, _c_, of the same, also - rectangular in section. The weir crest is at level _dd_, from 2 to 7 - cm. below the maximum level of water surface which it is desired not - to exceed in the supply basin. - -[Illustration: FIG. 28.] - - The descending branch, _c_, has at its base a small tank _e_, which - forms a water seal. The syphon is completed by a tube _f_, which is - attached to the intake branch of the syphon and which ends at a level - of 2 to 7 cm. above the previously mentioned surface _dd_. - - As soon as the water surface in the supply basin tends to rise above - the plane _dd_, a filament of water, in falling over the weir _b_, - pours down the descending branch _c_, and when the water has risen - from 2 to 7 cm. above the crest of the weir, the thickness of the - falling stream has become such that it is able, by lapping, with a - wave-like course, the wall _gg_, to extract the air that has become - enclosed in the syphon, and which cannot be replaced because the space - in which the stream acts is closed at its base by the water in the - tank _e_; and at the top also the aeration tube is closed by the rise - in the water surface of the supply basin. From this point the syphon - action quickly becomes fully established and begins to give its full - discharge. - - The discharge that is given is equal to that of an orifice in a thin - partition if certain limitations are allowed for between the fall used - in the syphon and the height of the arch, that is, the distance from - the crest of the weir to the inside roof of the syphon. - - The discharge is given by the formula - - Q = μA√(2_g h_). - - Q = discharge of syphon in cubic metres per sec. - - μ = a coefficient of reduction of discharge which varies between wide - limits. - - A = the minimum cross-sectional area of the syphon in square metres. - - _g_ = value of acceleration due to gravity. - - _h_ = the fall, or the difference of level in metres between the water - surfaces in the supply basin A and in the small tank _e_. - - As soon as the supply basin surface falls, the opening of the aeration - tube becomes uncovered and air is drawn into the syphon. But until the - surface has fallen some centimetres the supply of air is not - sufficient to cause the syphon action to stop completely, and thus the - escape varies gradually from the maximum discharge to zero as the - water surface falls a few centimetres till it reaches its original - level. - - In certain cases it is possible to do without the aeration tube, - especially when the fall used in the syphon is not great and when it - is possible to arrange matters so that the velocity of the water - flowing past in front of the syphon is small. - - The syphon with a width of 3 metres escapes 8 cubic metres per sec. of - water. - - -APPENDIX G. - -GAUGES. - -(See Chap. III., Arts. 2 and 3; also see _Hydraulics_, Chap. VIII., Art. -5, and Appendix H.) - -1. The gauge should be placed on that bank and facing in that direction -which enables it to be most conveniently read by the gauge reader and by -officials passing the place. - -2. The gauge should be of enamelled iron secured by copper screws to a -post of squared and seasoned wood which is either driven beforehand[64] -into the channel or spiked to a masonry work. Even in the deepest -channel a long enough post can be arranged for. A masonry pillar is not -necessary. The post may be rectangular in cross-section, with upstream -and downstream edges cut sharp. This prevents, or greatly reduces, the -heaping up of water at the upstream side and the formation of a hollow -downstream. If the “Ward” gauge of two vertical planks is used, the -planks should meet at an acute angle, not a right angle, and not be -wider than 7 inches each. - - [64] Driving after the gauge is attached may loosen or break the - screws. - -3. The top of the gauge should be slightly above the highest probable -water-level. The post should extend up to the top of the gauge. - -4. If ever the graded bed of the channel is altered the zero of the -gauge should be altered. There may be some risk of confusion at first, -but it can be avoided by exercising due care and making notes. The -levels of the old and new zeros should be recorded. - -5. A gauge at a distance from the bank is objectionable. It collects -jungle, cannot be properly read, and is liable to be damaged by floating -logs or boats. A gauge should be as near as possible to one bank or the -other. If the bank is vertical, the gauge should be quite close to it. -If, owing to silt deposit, the gauge is dry at low supply, the deposit -can be removed by the gauge reader. - -6. Every regulator should be given a name, generally that of a -neighbouring village and not that of a channel, and the gauge book -headings should be drawn up in an intelligent and systematic manner. -Each main channel should be entered in order, and each regulator on the -channel--together with the head gauges of all channels which take off -there--should be entered, commencing from upstream. A specimen is given -on page 109. Thus the head gauge of any branch appears in the register -of the main channel from which it takes off, other gauges on the branch -appearing in the register for the branch. And similarly as regards a -distributary which has gauges other than the head gauge. - -7. Each gauge reader should be supplied with a register, each page -having, besides the counterfoil, as many detachable slips--marked off by -perforations--as there are officials--usually the Subdivisional Officer, -zilladar and suboverseer--to whom daily gauge reports are to be sent. -The titles and addresses of these officials are printed on the backs of -the respective slips. The slips and counterfoil have printed on them a -form--similar to part of the specimen shown on page 109--showing the -names of all the gauges read by that particular gauge reader, so that -he has merely to fill in the date and readings, tear off the slips and -despatch them. The posting of the register in the subdivision is -facilitated if each gauge has a number and if the corresponding numbers -are printed--besides the names--on the gauge slips. If the gauge reader -does not know English, the headings of the slips are printed in the -vernacular. If the gauge readings are telegraphed, there may be only one -slip--besides the counterfoil--which is sent to the telegraph -signaller. - - -APPENDIX H. - -GIBB’S MODULE.[65] - -(See p. 164.) - - [65] This description has been supplied by Glenfield & Kennedy, - Kilmarnock. The modules can, it is understood, be obtained from them. - -The attributes of a perfect module are many and varied, but in Gibb’s -module they have all been successfully embodied in what is probably the -simplest piece of apparatus of its kind ever devised. The following -summary of the characteristics of Gibb’s module is, therefore, -equivalent to an enumeration of the attributes of a perfect module:-- - - Gibb’s module - - Cannot be tampered with, } - Cannot get out of order, } since it has no moving - Silt or other solid matter in the water } parts, and because of its - cannot affect its action, } extreme simplicity. - Requires no attention, } - - It is accurate, } being designed on scientific - Works with very small loss of head, } hydraulic principles. - - It is portable, and can be erected at any desired site very simply and - easily. - - It is strong and durable. - - The range of variation of both up- and downstream water-levels through - which the discharge remains constant is more than sufficient to meet - all the requirements of irrigation canals. - - The sufficiency of the delivery can be ascertained at a glance. - - The water can be drawn from any desired depth in the parent channel. - - When desired, means are provided whereby the supply can be closed or - opened at will. - - Means are provided, if desired, for a sudden increase of discharge - when the upstream water-level exceeds a certain limit, so that surplus - water, which might endanger the safety of the canal, is allowed to - escape into the branch whenever the danger limit is reached. The - upstream water-level at which escapement begins can be fixed in - accordance with the requirements of each site, and the action of the - escape notch is independent of the opening and closing of the module. - - No designing or calculations are required. These have already been - worked out. Known the discharge required, the module is supplied - complete and ready for setting in position in the canal bank. - - -HYDRAULIC PRINCIPLE. - -The entire absence of moving parts is the chief feature of Gibb’s -module; the water simply regulates itself by using up all the excess of -energy over and above that required to discharge the correct supply of -water. The way in which this takes place will be understood from the -following analogy:-- - -We all know that when we stir tea in a cup so as to make it spin, the -liquid rises at the rim of the cup and curves down into a depression in -the middle, and the greater the spin the more marked this effect is. It -is, we know, the centrifugal force produced by the spin that makes the -tea remain high at the rim of the cup. If, while the tea is thus -spinning, a teaspoon is held so that it dips slightly below the surface -of the liquid near the rim, it will obstruct the flow of the outer -portion of the liquid, which will fall in towards the depression in the -middle. The reason for this, of course, is that the centrifugal force is -absorbed when we interrupt any part of the spin with the teaspoon; hence -the liquid must fall, and we know that when liquid falls it uses up -“head” or energy. - -In Gibb’s module a similar action is made to take place in a steel -chamber, semicircular or spiral in plan, through which the water flows -in a semicircular path instead of circulating round and round as in the -teacup. The surface of the stream, however, assumes the same form as it -does in a cup, because it flows under the same conditions. Across the -chamber are fixed a number of vertical steel diaphragm plates which take -the place of the teaspoon in the above analogy. The lower edges of these -plates are of such a shape, and they are fixed at such a height from the -bottom of the chamber, as to allow a stream of just the correct required -discharge of water to flow under them without interference. But if, -owing to an increase of head caused by a rise in the upstream -water-level, the water tends to rise higher at the circumference of the -chamber, then the water at the surface of the stream strikes against the -diaphragm plates, and its centrifugal force being absorbed, it will fall -in towards the centre just as happened in the teacup when the spoon was -used in place of these plates. In this way the excess head that caused -the additional rise of water at the circumference is used up by the fall -back towards the centre. The full capacity of the semicircle or spiral -for using up excess head or energy in this way is made available by the -use of a sufficient number of diaphragm plates fixed at suitable -intervals. When the range of head to be dealt with is not large, then a -semicircular chamber is sufficient; but for large ranges of head the -chamber is made of spiral form so as to lead the water round a complete -revolution or more, as may be necessary. - - -STRUCTURAL DETAILS. - -Fig. 29 shows the general form and structure of the type of module -suitable for irrigation. Fig. 30 is from a photograph. - -The working chamber or shell A is constructed of mild steel plating -securely riveted to a framework of angle steel, and the semicircular -form of the shell with the rigid diaphragm plates B B riveted to the -walls makes a very strong structure, and ensures durability. - -The “leading-in” bend C is of cast iron strongly bolted to the steel -shell, and is so designed as to deliver the water into the module -chamber in a completely established vortex condition. - -The socket D on this “leading-in” bend is made so as to allow of -considerable latitude in the vertical alignment of the straight -leading-in pipe, so that the water can be drawn from any desired depth -in the parent channel, and the proportion of silt drawn off is thus -brought under control. - -[Illustration: -- END ELEVATION. -- - --- PLAN. -- - --- FRONT ELEVATION. -- - -FIG. 29.--Details of Gibb’s Patent Module.] - -Grooves E E and a shutter F, as illustrated, for closing off the flow -through the module, are provided, if required, but all modules are not -fitted in this way, because many irrigation authorities consider it -undesirable to provide the consumers with unrestricted facilities for -closing off their supplies without previously giving notice of such an -action. - -[Illustration: FIG. 30.--The Completed Module (Open Type for Low -Heads).] - -An escape notch H is provided in the position indicated when desired. It -may, however, be found difficult to determine beforehand the upstream -water-level at which it is necessary to allow this escape of surplus -supply, so that it is generally more satisfactory to cut the escape -notch after the modules have been installed and actual experience has -indicated a suitable level for the notch crest. - -In the standard type of module for irrigation purposes the top of the -module chamber is completely open, as shown, and this is the type -generally recommended, as it is found that consumers have greater -confidence in an apparatus which hides nothing from them. To meet the -needs of special cases, however, a second type is also made in which the -chamber is completely closed and considerably reduced in height, being -thus specially suitable for sites where space is confined. - -Pipes I, of diameter suitable for all sizes of modules, are also -supplied. These may either be welded steel or cast iron, as desired. An -18-feet length of pipe is usually found sufficient to bring the supply -through the canal bank to the module. - -All modules supplied are treated with anti-corrosive paint, which -ensures the protection of the metal. - - -APPENDIX K. - -KENNEDY’S GAUGE OUTLET.[66] - -(See p. 168.) - - [66] See _Punjab Irrigation Branch Paper No. 12_, “Results of Tests of - Kennedy’s Gauge Outlet.” - -FIG. 31 shows a bell-mouthed orifice discharging into an air-space. The -jet springs across the air-space and traverses a gradually diverging -tube. Let _a_, A be the sectional areas of the stream at the air-space -and the downstream end of the tube respectively, and let V, _v_, and -P_ₐ_, P₁ be the corresponding velocities and pressures. Let resistances -be neglected. Since the pressure in the air-space is P_ₐ_, - - V = √(2_g h_₀) - -or the discharge through the tube depends only on _h_₀ and not on _h_₁. - -[Illustration: FIG. 31.] - -By Bernouilli’s theorem, - - V² P_ₐ_ _v_² P₁ - ---- + ---- = ----- + -- - 2_g_ W 2_g_ W - -or - - P₁ - P_ₐ_ V² - _v_² - --------- = ---------. - W 2_g_ - -This quantity (since _v_ is small) is not much less than _h_₀ or -V²/2_g_. In other words, the water levels of two cisterns with an -air-space between them differ only a little, or _h_₁ is small. - -The above case (two cisterns and air-space) is mentioned in -_Hydraulics_, Chap. V. The principle is simply that the velocity head at -the air-space is reconverted into pressure head by passing the stream -through a gradually diverging tube. In the absence of such a tube the -velocity head would be wasted by causing eddies in the downstream -cistern. - -If the downstream cistern is a watercourse whose water-level is -considerably lower than that of the upstream cistern or distributary, V -is obviously unaffected. Also P₁ is obviously reduced. Therefore, by -Bernouilli, _v_ is increased, or the stream does not fill the expanded -tube and there are eddies in the tube. The water-level in the -watercourse may even be lower than the end of the tube. The discharge is -unaffected. - -In practice there are, of course, resistances, but this fact does not -affect the general conclusions stated above. The minimum working head -(difference between the two water-levels) which gives a constant -discharge is greater than would be the case in the absence of -resistances. This “minimum working head for modularity” has been found -to be ·21 foot, ·42 foot, and ·61 foot, the corresponding values of the -“depression,” _h_₀, being respectively 1 foot, 2 feet, and 3 feet. When -the working head is less than the above, the discharge is less and it -depends on the working head. The depression should, according to -Kennedy, be about 1·75 feet, but it may be more. - -The chief difficulty in using the gauge outlet as a module is that the -air vent can be stopped up. This converts the apparatus into a compound -diverging tube (_Hydraulics_, Chap. III., Art. 17). The discharge is, of -course, increased, and it becomes dependent at all times on the working -head. Another difficulty is that any rise or fall in the water-level of -the distributary (and such rises and falls may occur owing to silting or -scour, however carefully the discharge may be regulated) alters the -discharge somewhat, though not to the same degree as in an ordinary -outlet with a working head of, say, ·5 foot. In short, Kennedy’s gauge -outlet, or “semi-module” as it is sometimes called, can modify but not -do away with the variations of the discharges of outlets. - - - - -INDEX. - - - Absorption, 16, 159. - Alignment, principles of, 4. - Alignment, centrality in, 5. - Alteration in line, 59. - Assiut Barrage, 11. - Assouan Dam, 11. - - Banks, construction of, 138. - -- protection of, 139, 175, 178. - -- width and height of, 56. - Banks and Roads, 53. - Basin Irrigation, 11. - Berms, 53. - Bifurcations, 47. - Bifurcation, head needed at, 45. - Borrow pits, 55. - Branches of Canals, 3. - Breaches in Banks, 176. - Bricks used for canal work in India, 88. - Bridges, 8, 80, 87, 130. - -- Skew, 29, 42. - Bushing of banks, 178. - - Canal and branches, 20, 47. - Canal, bed width of, 51. - -- supplied from reservoirs, 3, 13. - -- inundation, 1, 45, 79, 127, 156. - -- perennial, 1. - Capillarity, 16. - Cattle Gháts, 81, 173. - Cement for lining channels, 160. - Chainage, 93, 118. - Channels, alterations in, 97. - -- enlargement of, 97, 139. - -- gradients of, 50. - -- side slopes of, 52. - Colonization Schemes, 64. - Command, 2. - Commanded area, 4. - Contour lines, 37. - -- plan, 26, 36, 63. - -- survey, 37. - Crops, failure of, 103, 142. - -- kinds of, 101. - Culturable commanded area, 26, 113. - Curves and bends in channels, 8, 139. - - “Delta,” 22, 110. - Deputy Collector, 96. - Designs and Estimates, 60. - Design of canals, 2, 26, 30, 47, 147, 156. - Discharge of canal during rabi, 52, 118. - Discharge observations, 107. - Discharges of Punjab rivers, 145, 157. - Discharge tables, 106. - -- through an outlet, 61. - Distance marks, 93. - Distribution of water, 14, 118, 125. - Distributaries, 3, 20, 44, 46. - -- best system of, 71. - Distributary, bed width of, 68. - -- design of, 60. - -- height and width of banks, 68. - -- kharif, 156. - -- longitudinal section of, 69. - -- major and minor, 41. - -- off-take of, 51. - -- remodelling of, 128. - -- side slopes of, 69. - -- strip of land for, 69. - -- with three fourths full supply, 45, 68, 166. - Divide Walls, 33, 169. - Divisions, canal, 96. - Drainage, 10. - Drainage Crossings, 8, 156. - Duty of water, 21, 25, 39, 148, 153, 154. - Duty, improvement of, 24, 102, 158. - - Eastern Jumna Canal, 31. - Efflorescence called “Reh,” 15. - Egypt, irrigation in, 11. - Embankments, 9, 33, 156. - Escapes, 9, 100, 180. - Estimates for work, 59. - Evaporation, 16. - Executive Engineer, 96. - Extensions of canals, 127. - Extra land, 58. - - Falling Shutters, 32. - Falls, 8, 81, 87. - -- incomplete, 87, 130. - -- notch, 86. - Field book, 101. - -- map, 101. - -- register, 101. - Final line, 59. - Flow and lift, 11. - Full supply duty, 64. - Full supply factor, 64. - - Ganges Canal, 31. - Gauges, 10, 103, 104, 183. - Gauge reader, 96, 98, 105, 184. - Gauge reading, 105, 121. - -- register, 105, 106, 108, 111. - Gibb’s module, 164, 186. - Guide banks, 35. - - Head for distributary, 82, 83. - Headworks, 2, 30, 98, 99, 137. - - Indents for water, 98, 108, 110. - Inundation canals, 1, 45, 79, 127, 156. - Irrigation boundaries, 33, 129. - -- in various countries, 1. - -- registers, 113. - -- unauthorised, 101. - - Kennedy’s gauge outlet, 168, 193. - -- Rules for channel design, 48. - Kharif or Summer Crop, 23. - Kutter’s co-efficients, 51. - - Lift irrigation, 11, 142. - Lime for making channels watertight, 162. - Longitudinal section, 69, 130. - Losses of water in channels, 16, 38, 159. - Low supplies, 118, 123. - Lower Chenab Canal, 25, 144. - Lower Egypt, 11. - Lower Jhelum Canal, 144. - - Maintenance work, 138, 171, 174. - Marginal Embankments, 9. - Masonry works, 29, 80, 89. - -- -- large scale site plan, 89. - -- -- type designs, 89. - Mills, 8. - Minors, question of desirability of, 75. - Modules, 162, 186. - - Navigation, 12. - Needles and horizontal planks, 85. - - Oil for lining channels, 160. - Older Indian canals, 10, 68, 98. - Outlet, discharge of, 61. - -- registers, 113. - Outlets, 15, 61, 66, 67. - -- applications regarding, 140. - -- design of, 76. - -- on inundation canals, 79. - -- on older canals, 68. - -- positions of, 65. - -- remodelling of, 131. - -- register of, 113. - -- size of, 114, 134. - -- temporary, 78. - -- variability of duty on, 66. - - Parapets, width between, 77. - Patwari, 96, 101. - Percolation, 16. - Perennial Canals, 1. - Pitching, 90. - Plan, large scale, 59. - Postal system, 97. - Profile walls, 91, 94. - Project, sketch of, 26. - Proportion of land to be irrigated, 27, 156. - Puddle for lining channels, 160. - Punjab, projects for canals in, 144. - Punjab rivers, 145, 147. - - Quarters for regulating staff, 88. - - Rabi or winter crop, 23. - Railings, 88. - Rain, 9, 22, 100. - Ramps, 88. - Ratio of bed width to depth, 50. - Reduction in size of channel, 128. - Registers, irrigation, 113. - Regulation of supply, 103, 121, 127. - Regulators, 7, 80, 84, 184. - -- permissible heading up, 85. - Remodellings of channels, 127. - -- of outlets and watercourses, 131, 134. - Rest Houses, 95. - Reservoirs, 13. - Rules for designing canals, Kennedy’s, 48. - - Scheme, cost of, 28, 59. - Sides, falling in of, 139. - Sidhnai canal minors, 41. - Silt, clearance of, 97, 138, 139. - -- deposit, 15, 97. - -- trapping at Headworks, 47. - Silting and scouring, 15, 48, 98, 139. - Sirhind Canal, 19, 144. - -- -- silting in the head reach of, 98. - Soil, water-logging of, 10, 24, 102. - Spoil Banks, 52, 57. - Subdivisions, canal, 95. - Subdivisional officer, 96. - Suboverseer, 96. - Superintending Engineer, 96. - Supply carried, 100. - -- distribution of, 14, 118. - -- mean and full, 27, 46, 122. - -- regulation of, 103, 104, 106, 127. - Syphons, 7, 71, 87, 181. - - Tailing of one channel into another, 40. - Telegraph, line of, 97. - Training of rivers, 33. - Trial lines, 58. - Trial pits, 58. - Triple canal project, 144. - Tunnels, 13. - Turns, or rotational periods of flow, 14, 118. - Type cross sections, 56. - - Under-sluices, 32. - Upper Bari Doab Canal, 19, 144. - -- Chenab Canal, 33, 144. - -- Egypt, 11. - Upper Jhelum Canal, 50, 144. - - Velocity, 12, 50. - Village lands, 62. - - Watching banks, 175. - Water, payment for, 12, 100, 102, 142, 143. - Water level, fluctuation in, 100, 124. - Watercourse, limit of size of, 74. - Watercourses, 4, 20, 65. - -- applications regarding, 140. - -- for trees, 58. - -- remodelling of, 131. - -- with poor command, 67, 133, 166. - Waterings, 11, 24. - Water-logging of the soil, 10, 24, 102. - Wave, travel of, down a channel, 124. - Western America, canals in, 12. - -- Jumna Canal, 31, 39. - Wing Walls, 89. - Works, arrangement of, 89. - -- two or more close together, 89. - -- urgent repairs of, 137. - - Zilladar, 96. - - -Harvey & Healing, Printers, Manchester Street, Cheltenham. - - - - - Transcriber’s Notes - - - The inconsistent use of periods after Roman numerals has been - retained; other inconsistencies (spelling, hyphenation, formatting and - lay-out) have been retained as well, except when mentioned below. - - Depending on the hard- and software used and their settings, not all - elements may display as intended. Some of the tables are best viewed - in a wide window. - - Page 21: The equation does not agree with the calculations given. - - Page 66, Fig. 11: There are two illustrations labelled Fig. 11, the - hyperlinks point to the appropriate illustration. - - - Changes made - - Obvious typographical errors have been corrected silently. Footnotes - and illustrations have been moved out of text paragraphs. Some tables - have been re-arranged or split; in several tables, the data alignment - has been standardised. - - Page 18, table, Total of second column: 8·93 changed to 8·01 - Page 39: Kutters changed to Kutter’s - Page 93: marked out changed to marked at - Page 69: 3 Depth of digging changed to 13. Depth of digging - Page 109, first average ·1 changed to 4·1 - Page 117: Net Areas Irrigated in Areas changed to Net Areas Irrigated - in Acres - Page 150: Cusecs. added as in similar tables - Index: Cattle Ghats changed to Cattle Gháts; Line for making ... - changed to Lime for making ...; Lower Chenal Canal changed to Lower - Chenab Canal. - - - - - -End of the Project Gutenberg EBook of Irrigation Works, by E. S. Bellasis - -*** END OF THIS PROJECT GUTENBERG EBOOK IRRIGATION WORKS *** - -***** This file should be named 56113-0.txt or 56113-0.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/5/6/1/1/56113/ - -Produced by Chris Curnow, Harry Lame -and the Online Distributed Proofreading Team at -http://www.pgdp.net (This file was produced from images -generously made available by The Internet Archive) - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. Special rules, set forth in the General Terms of Use part -of this license, apply to copying and distributing Project -Gutenberg-tm electronic works to protect the PROJECT GUTENBERG-tm -concept and trademark. Project Gutenberg is a registered trademark, -and may not be used if you charge for the eBooks, unless you receive -specific permission. If you do not charge anything for copies of this -eBook, complying with the rules is very easy. You may use this eBook -for nearly any purpose such as creation of derivative works, reports, -performances and research. They may be modified and printed and given -away--you may do practically ANYTHING in the United States with eBooks -not protected by U.S. copyright law. Redistribution is subject to the -trademark license, especially commercial redistribution. - -START: FULL LICENSE - -THE FULL PROJECT GUTENBERG LICENSE -PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK - -To protect the Project Gutenberg-tm mission of promoting the free -distribution of electronic works, by using or distributing this work -(or any other work associated in any way with the phrase "Project -Gutenberg"), you agree to comply with all the terms of the Full -Project Gutenberg-tm License available with this file or online at -www.gutenberg.org/license. - -Section 1. General Terms of Use and Redistributing Project -Gutenberg-tm electronic works - -1.A. By reading or using any part of this Project Gutenberg-tm -electronic work, you indicate that you have read, understand, agree to -and accept all the terms of this license and intellectual property -(trademark/copyright) agreement. If you do not agree to abide by all -the terms of this agreement, you must cease using and return or -destroy all copies of Project Gutenberg-tm electronic works in your -possession. If you paid a fee for obtaining a copy of or access to a -Project Gutenberg-tm electronic work and you do not agree to be bound -by the terms of this agreement, you may obtain a refund from the -person or entity to whom you paid the fee as set forth in paragraph -1.E.8. - -1.B. "Project Gutenberg" is a registered trademark. It may only be -used on or associated in any way with an electronic work by people who -agree to be bound by the terms of this agreement. There are a few -things that you can do with most Project Gutenberg-tm electronic works -even without complying with the full terms of this agreement. See -paragraph 1.C below. There are a lot of things you can do with Project -Gutenberg-tm electronic works if you follow the terms of this -agreement and help preserve free future access to Project Gutenberg-tm -electronic works. See paragraph 1.E below. - -1.C. The Project Gutenberg Literary Archive Foundation ("the -Foundation" or PGLAF), owns a compilation copyright in the collection -of Project Gutenberg-tm electronic works. Nearly all the individual -works in the collection are in the public domain in the United -States. If an individual work is unprotected by copyright law in the -United States and you are located in the United States, we do not -claim a right to prevent you from copying, distributing, performing, -displaying or creating derivative works based on the work as long as -all references to Project Gutenberg are removed. Of course, we hope -that you will support the Project Gutenberg-tm mission of promoting -free access to electronic works by freely sharing Project Gutenberg-tm -works in compliance with the terms of this agreement for keeping the -Project Gutenberg-tm name associated with the work. You can easily -comply with the terms of this agreement by keeping this work in the -same format with its attached full Project Gutenberg-tm License when -you share it without charge with others. - -1.D. The copyright laws of the place where you are located also govern -what you can do with this work. Copyright laws in most countries are -in a constant state of change. If you are outside the United States, -check the laws of your country in addition to the terms of this -agreement before downloading, copying, displaying, performing, -distributing or creating derivative works based on this work or any -other Project Gutenberg-tm work. The Foundation makes no -representations concerning the copyright status of any work in any -country outside the United States. - -1.E. Unless you have removed all references to Project Gutenberg: - -1.E.1. The following sentence, with active links to, or other -immediate access to, the full Project Gutenberg-tm License must appear -prominently whenever any copy of a Project Gutenberg-tm work (any work -on which the phrase "Project Gutenberg" appears, or with which the -phrase "Project Gutenberg" is associated) is accessed, displayed, -performed, viewed, copied or distributed: - - This eBook is for the use of anyone anywhere in the United States and - most other parts of the world at no cost and with almost no - restrictions whatsoever. You may copy it, give it away or re-use it - under the terms of the Project Gutenberg License included with this - eBook or online at www.gutenberg.org. If you are not located in the - United States, you'll have to check the laws of the country where you - are located before using this ebook. - -1.E.2. If an individual Project Gutenberg-tm electronic work is -derived from texts not protected by U.S. copyright law (does not -contain a notice indicating that it is posted with permission of the -copyright holder), the work can be copied and distributed to anyone in -the United States without paying any fees or charges. If you are -redistributing or providing access to a work with the phrase "Project -Gutenberg" associated with or appearing on the work, you must comply -either with the requirements of paragraphs 1.E.1 through 1.E.7 or -obtain permission for the use of the work and the Project Gutenberg-tm -trademark as set forth in paragraphs 1.E.8 or 1.E.9. - -1.E.3. If an individual Project Gutenberg-tm electronic work is posted -with the permission of the copyright holder, your use and distribution -must comply with both paragraphs 1.E.1 through 1.E.7 and any -additional terms imposed by the copyright holder. Additional terms -will be linked to the Project Gutenberg-tm License for all works -posted with the permission of the copyright holder found at the -beginning of this work. - -1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm -License terms from this work, or any files containing a part of this -work or any other work associated with Project Gutenberg-tm. - -1.E.5. Do not copy, display, perform, distribute or redistribute this -electronic work, or any part of this electronic work, without -prominently displaying the sentence set forth in paragraph 1.E.1 with -active links or immediate access to the full terms of the Project -Gutenberg-tm License. - -1.E.6. You may convert to and distribute this work in any binary, -compressed, marked up, nonproprietary or proprietary form, including -any word processing or hypertext form. However, if you provide access -to or distribute copies of a Project Gutenberg-tm work in a format -other than "Plain Vanilla ASCII" or other format used in the official -version posted on the official Project Gutenberg-tm web site -(www.gutenberg.org), you must, at no additional cost, fee or expense -to the user, provide a copy, a means of exporting a copy, or a means -of obtaining a copy upon request, of the work in its original "Plain -Vanilla ASCII" or other form. Any alternate format must include the -full Project Gutenberg-tm License as specified in paragraph 1.E.1. - -1.E.7. Do not charge a fee for access to, viewing, displaying, -performing, copying or distributing any Project Gutenberg-tm works -unless you comply with paragraph 1.E.8 or 1.E.9. - -1.E.8. You may charge a reasonable fee for copies of or providing -access to or distributing Project Gutenberg-tm electronic works -provided that - -* You pay a royalty fee of 20% of the gross profits you derive from - the use of Project Gutenberg-tm works calculated using the method - you already use to calculate your applicable taxes. The fee is owed - to the owner of the Project Gutenberg-tm trademark, but he has - agreed to donate royalties under this paragraph to the Project - Gutenberg Literary Archive Foundation. Royalty payments must be paid - within 60 days following each date on which you prepare (or are - legally required to prepare) your periodic tax returns. Royalty - payments should be clearly marked as such and sent to the Project - Gutenberg Literary Archive Foundation at the address specified in - Section 4, "Information about donations to the Project Gutenberg - Literary Archive Foundation." - -* You provide a full refund of any money paid by a user who notifies - you in writing (or by e-mail) within 30 days of receipt that s/he - does not agree to the terms of the full Project Gutenberg-tm - License. You must require such a user to return or destroy all - copies of the works possessed in a physical medium and discontinue - all use of and all access to other copies of Project Gutenberg-tm - works. - -* You provide, in accordance with paragraph 1.F.3, a full refund of - any money paid for a work or a replacement copy, if a defect in the - electronic work is discovered and reported to you within 90 days of - receipt of the work. - -* You comply with all other terms of this agreement for free - distribution of Project Gutenberg-tm works. - -1.E.9. If you wish to charge a fee or distribute a Project -Gutenberg-tm electronic work or group of works on different terms than -are set forth in this agreement, you must obtain permission in writing -from both the Project Gutenberg Literary Archive Foundation and The -Project Gutenberg Trademark LLC, the owner of the Project Gutenberg-tm -trademark. Contact the Foundation as set forth in Section 3 below. - -1.F. - -1.F.1. Project Gutenberg volunteers and employees expend considerable -effort to identify, do copyright research on, transcribe and proofread -works not protected by U.S. copyright law in creating the Project -Gutenberg-tm collection. Despite these efforts, Project Gutenberg-tm -electronic works, and the medium on which they may be stored, may -contain "Defects," such as, but not limited to, incomplete, inaccurate -or corrupt data, transcription errors, a copyright or other -intellectual property infringement, a defective or damaged disk or -other medium, a computer virus, or computer codes that damage or -cannot be read by your equipment. - -1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right -of Replacement or Refund" described in paragraph 1.F.3, the Project -Gutenberg Literary Archive Foundation, the owner of the Project -Gutenberg-tm trademark, and any other party distributing a Project -Gutenberg-tm electronic work under this agreement, disclaim all -liability to you for damages, costs and expenses, including legal -fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT -LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE -PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE -TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE -LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR -INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH -DAMAGE. - -1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a -defect in this electronic work within 90 days of receiving it, you can -receive a refund of the money (if any) you paid for it by sending a -written explanation to the person you received the work from. If you -received the work on a physical medium, you must return the medium -with your written explanation. The person or entity that provided you -with the defective work may elect to provide a replacement copy in -lieu of a refund. If you received the work electronically, the person -or entity providing it to you may choose to give you a second -opportunity to receive the work electronically in lieu of a refund. If -the second copy is also defective, you may demand a refund in writing -without further opportunities to fix the problem. - -1.F.4. Except for the limited right of replacement or refund set forth -in paragraph 1.F.3, this work is provided to you 'AS-IS', WITH NO -OTHER WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT -LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE. - -1.F.5. Some states do not allow disclaimers of certain implied -warranties or the exclusion or limitation of certain types of -damages. If any disclaimer or limitation set forth in this agreement -violates the law of the state applicable to this agreement, the -agreement shall be interpreted to make the maximum disclaimer or -limitation permitted by the applicable state law. The invalidity or -unenforceability of any provision of this agreement shall not void the -remaining provisions. - -1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the -trademark owner, any agent or employee of the Foundation, anyone -providing copies of Project Gutenberg-tm electronic works in -accordance with this agreement, and any volunteers associated with the -production, promotion and distribution of Project Gutenberg-tm -electronic works, harmless from all liability, costs and expenses, -including legal fees, that arise directly or indirectly from any of -the following which you do or cause to occur: (a) distribution of this -or any Project Gutenberg-tm work, (b) alteration, modification, or -additions or deletions to any Project Gutenberg-tm work, and (c) any -Defect you cause. - -Section 2. Information about the Mission of Project Gutenberg-tm - -Project Gutenberg-tm is synonymous with the free distribution of -electronic works in formats readable by the widest variety of -computers including obsolete, old, middle-aged and new computers. It -exists because of the efforts of hundreds of volunteers and donations -from people in all walks of life. - -Volunteers and financial support to provide volunteers with the -assistance they need are critical to reaching Project Gutenberg-tm's -goals and ensuring that the Project Gutenberg-tm collection will -remain freely available for generations to come. In 2001, the Project -Gutenberg Literary Archive Foundation was created to provide a secure -and permanent future for Project Gutenberg-tm and future -generations. To learn more about the Project Gutenberg Literary -Archive Foundation and how your efforts and donations can help, see -Sections 3 and 4 and the Foundation information page at -www.gutenberg.org Section 3. Information about the Project Gutenberg -Literary Archive Foundation - -The Project Gutenberg Literary Archive Foundation is a non profit -501(c)(3) educational corporation organized under the laws of the -state of Mississippi and granted tax exempt status by the Internal -Revenue Service. The Foundation's EIN or federal tax identification -number is 64-6221541. Contributions to the Project Gutenberg Literary -Archive Foundation are tax deductible to the full extent permitted by -U.S. federal laws and your state's laws. - -The Foundation's principal office is in Fairbanks, Alaska, with the -mailing address: PO Box 750175, Fairbanks, AK 99775, but its -volunteers and employees are scattered throughout numerous -locations. Its business office is located at 809 North 1500 West, Salt -Lake City, UT 84116, (801) 596-1887. Email contact links and up to -date contact information can be found at the Foundation's web site and -official page at www.gutenberg.org/contact - -For additional contact information: - - Dr. Gregory B. Newby - Chief Executive and Director - gbnewby@pglaf.org - -Section 4. Information about Donations to the Project Gutenberg -Literary Archive Foundation - -Project Gutenberg-tm depends upon and cannot survive without wide -spread public support and donations to carry out its mission of -increasing the number of public domain and licensed works that can be -freely distributed in machine readable form accessible by the widest -array of equipment including outdated equipment. Many small donations -($1 to $5,000) are particularly important to maintaining tax exempt -status with the IRS. - -The Foundation is committed to complying with the laws regulating -charities and charitable donations in all 50 states of the United -States. Compliance requirements are not uniform and it takes a -considerable effort, much paperwork and many fees to meet and keep up -with these requirements. We do not solicit donations in locations -where we have not received written confirmation of compliance. To SEND -DONATIONS or determine the status of compliance for any particular -state visit www.gutenberg.org/donate - -While we cannot and do not solicit contributions from states where we -have not met the solicitation requirements, we know of no prohibition -against accepting unsolicited donations from donors in such states who -approach us with offers to donate. - -International donations are gratefully accepted, but we cannot make -any statements concerning tax treatment of donations received from -outside the United States. U.S. laws alone swamp our small staff. - -Please check the Project Gutenberg Web pages for current donation -methods and addresses. Donations are accepted in a number of other -ways including checks, online payments and credit card donations. To -donate, please visit: www.gutenberg.org/donate - -Section 5. General Information About Project Gutenberg-tm electronic works. - -Professor Michael S. Hart was the originator of the Project -Gutenberg-tm concept of a library of electronic works that could be -freely shared with anyone. For forty years, he produced and -distributed Project Gutenberg-tm eBooks with only a loose network of -volunteer support. - -Project Gutenberg-tm eBooks are often created from several printed -editions, all of which are confirmed as not protected by copyright in -the U.S. unless a copyright notice is included. Thus, we do not -necessarily keep eBooks in compliance with any particular paper -edition. - -Most people start at our Web site which has the main PG search -facility: www.gutenberg.org - -This Web site includes information about Project Gutenberg-tm, -including how to make donations to the Project Gutenberg Literary -Archive Foundation, how to help produce our new eBooks, and how to -subscribe to our email newsletter to hear about new eBooks. - |