52 BULLETIN 339, U. S..DEPARTMENT OF AGRICULTURE, 
A study of the results shows, among other things: 
(1) Small laterals carrying 1 second-foot and less almost inva- 
riably lose a large part of the water carried, and the percentage of 
loss decreases rapidly as the volume carried is increased, thus empha- — 
sizing the desirability of rotation systems where the necessity of 
carrying small amounts is eliminated. 
(2) Since certain types of soil have a fairly uniform loss per square 
foot of canal bed, canals should be designed, other things being 
equal, with as small a wetted perimeter as possible in comparison to 
their cross sections. 
(3) Porous irrigated land above a canal may cause it to gain 
instead of lose. 
(4) Canals in average southern Idaho soil, which is a medium clay 
loam, should be designed to withstand a loss of 0.5 to 1.5 cubic feet 
per square foot of canal bed in 24 hours; 0.5 cubic foot per square foot 
pet day is a safe basis for impervious clay loam soil, about 1 cubic 
foot per day for medium soil, and 1.5 to 2 cubic feet per square foot 
per day is a safe basis for somewhat pervious soils. 
(5) One per cent per mile is a safe basis for the loss in medium 
southern Idaho soil with capacities in excess of 200 second-feet. 
(6) Canals in gravelly soil should be designed to withstand a loss 
of 2.5 to 5 cubic feet per square foot of canal bed in 24 hours, depend- 
ing upon the porosity of the gravel, although it is probable that lining 
would be profitable if the higher loss were experienced. The pro- 
cedure must be determined by local economic conditions. 
(7) A project having a comparatively long main canal, constructed 
through earth and unlined, may lose from 20 to as high as 50 per 
cent of the water diverted before it reaches the farms even in the 
impervious soils. (See fig. 13.) 
SURVEY OF WASTE LAND IN IDAHO. 
It has long been known that not every acre of the gross area con- 
tained in a project is irrigated. Engineers, for lack of more accurate 
data, have commonly assumed that 20 per cent of a typical project 
is unirrigated because of high spots, corrals, county and private roads, 
railroad rights of way, etc. Water has been increasing in value to 
such an extent that there is a great incentive to base projects upon 
narrower margins each year, and it was evident that the above factor 
should be carefully determined in order to allow of a design that 
would not only be economical but would safeguard the future of the 
newer projects. For the purpose of determining the extent of unirri- 
gated land which exists in a high-class, intensively cultivated project 
in any one year from all causes, 16,067.8 acres of typical irrigated 
land, located in two contiguous bodies in the best part of two typical 
