RURAL ENGINEERING. 

 Absorption louses on canals. 



683 



I'Hrticiilars. 



Loss in cusees per mil- 

 lion square feet of 

 water surface. 



Mini- I Maxi- Aver- 

 mum. I mum. age. 



Main lino , 



Branches , 



l)istributaries ... 

 Water courses . .. 



On fields 



Mainline 



(First 26 miles.) 



Rrauches 



distributaries ... 

 Water courses . . . 

 On fields 



Ow Jiari Poab Canal — Good soil (jcnerally. 



Discharge about 4,000 cusees, depth about fi fl., all in 



shingle and sandy soil. 

 Discharges from 1,000 to 3,000 cusees, soil good loam not 



sandy, with silted berms, l)Ut no fine silt on bed. 

 Discharges 80 to 100 cusees, good loam soil, silted side 



berms and in lower reaches, fine silt on bed. 

 Discharges 0..i0 to 3.0 cusees, good loam soil, generally 



rough bed and banks, in all .sorts of conditions, some 



new. 

 When first water is laid on, sometimes soil was moist and 



in some cases quite dry. 



On Shiiind Canal — Samli/ soil t/eneraUy. 



Discharge about 4,000 cusees. depth about 7 ft., all in sandy 

 soil, no shingle, sand, .silteil bed, and no side berms. The 

 subsoil water table was close to surface an<l sloping 

 awav to the river from the canal at a grade of 2.4 ft. in 

 1,000. 



Discharges from 2,000 to 4,000 cusees, depth about 7 ft., all 

 sandy soil, little or no side berms, and sand on bed. 



Discharges 30 to 100 eusccs, all sandy soil, in all sorts of 

 conditions as to bed and l)('rms. 



Discharges 0.50 to 3.0 cu.sees, all sandy .soil in all sorts of 

 repair. 



When water is first laid on 



2.3 

 .3.3 



(5.0) 



(7.0) 



(12.0) 



4.4 

 30.0 



9.7 

 2.2 

 3.3 

 9.4 



5.2 

 (8.0) 

 (22.0) 

 (21.0) 



Eartlien dams, [A. ilii.Ll {[I'roc.} Inir/. (Jonf., Simla, WOJi, I, pp. .J.9-62).— 

 CoiisidtTahle iiifonnatioii is given relating to the sub.lect in general, and certain 

 opinions drawn from the experience of the writer are given in the following 

 notes : 



" The cross section of the bank should be proportionate to the depth of water, 

 and the slope from the point where the full suppl.v level touches the bank to the 

 outer toe should he not less than 4 to 1 for banks of ordiuar.v construction in less 

 than 40 ft. deiith of water. This line is the hydraulic gradient for the bank. 



" The earth in the bank will become saturated in time, and in high banks the 

 lower part will move and slip under the pressure of the upper portion and water, 

 unless held down by some material not affectecj by water. 



" For depths of water greater than 40 ft. the Ix'havior of tlie bank when satu- 

 r.-itcd is miccrtain, and tlie cross section must be grc.-itcr than fcir ;i l);ink of less 

 depth. 



"Up to 40 ft. dciitli tlic section reconnnciidcd by the ■•intlior has a core of 

 selected w.ater-tiglit eartii 10 ft. wide at highest flood jrvcl. and with side 

 slopes H to 1 on both sides, 'fills core is to l)e ]H'otected on tlie top and water 

 sid(> by material not likely to slij) when wet, like the soft mooi'um of (h'composed 

 lock of the Deccan, and the slojie on the water face may l)e '21 to 1 or 3 to 1. 



"The water-tight core slicmld be covered on the rear slojie by a mass of mate- 

 i-jal not affected by water, and, to keep the <>arth from being forced into the 

 drainage material, it should be arranged like a filter, with soft moorum on the 

 inside against the earth core and large coarse material (tn the outer side, broken 

 metal or screened gravel being very suitable for (lie outside. 



"At the rear toe provision must be made for the water to escape, and the toe 

 nuist be a mass of dry stone when tlu> foundations Jir<' good. 



"The best foundation for the rear toe of a bank is iiorous rock like moorum. 



