48 BULLETIN 126, U. S. DEPARTMENT OF AGRICULTURE. 



rier against the escape of water. If the bottom of a new canal in 

 porous material is covered with a layer of clay, moistened, and then 

 used as a feeding ground for domestic animals it may be rendered 

 quite impervious. Some of the thoroughly worked clay can after- 

 wards be removed from the bottom and placed on the slopes. When 

 domestic animals are not available to mix the clay, it should be done 

 by harrowing and packing. A layer of coarse gravel spread over* the 

 clay fining and tamped into it may prevent the erosion of the clay 

 and render it more effective. 



THE ECONOMY OF CONCRETE LINING. 



In determining the economy of concrete lining for a given canal, 

 one has to consider and compare the cost and benefits of such work. 

 Itemized statements of the cost of concrete lining for various canals 

 are given in another part of this report. The principal benefits to be 

 derived from fining are briefly discussed under the following heads: 



(1) Seepage water and its value. — The possible saving in seepage 

 losses by lining can be readily determined for canals already in use, 

 and the portions in which this is important can be located by measure- 

 ments of the discharge. In some cases the loss in short distances 

 may be sufficient to make the lining of these desirable, although it 

 would not be practicable to line the canal as a whole. 



In the case of a new canal, a reasonably close estimate of the seep- 

 age losses which are likely to occur may be made from the data given 

 in Table I. 



In nearly every irrigated district of the West water which can be 

 saved through the prevention of seepage has a value. As the demand 

 for water increases the value of any saving will also increase until 

 methods of canal lining at present too expensive to be considered may 

 become practicable. The value of the water which may be saved 

 varies widely in the different portions of the country. On the larger 

 systems now being constructed, water rights are being sold for from 

 $25 to $50 per acre, and in some cases for even higher prices. 



Based on the final estimated cost and acreage included, the average 

 estimated cost per acre July 1, 1910, was $48.14 for the United States 

 Keclamation Service projects and $21.75 for the Carey Act projects. 

 The duty of water delivered under these rights is also variable and 

 will probably average 1 second-foot to 100 acres. Inasmuch as any 

 saving in canal seepage can be delivered to the user with small addi- 

 tional loss, each 0.01 second-foot saved should make it possible to 

 serve another acre. The additional expense required for such irri- 

 gation would be for the lateral system only, as the storage and diver- 

 sion works would not be affected. On this basis each second-foot of 

 water which can be saved should have a value of from $2,500 to $5,000. 

 Allowing $750 for the additional cost of the distributing system leaves 



