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 hning 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 lining 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 hning 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 
Reclamation 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 
