36 BULLETIN 339, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE XIX.—Percentage of total supply wasted from surface. 
Percentage of waste. 
: Number of 
Crop. Class of soil. irrigations. 
Maximum.| Minimum.}| Average. 
Per cent. Per cent. Per cent. 
Alialiancs-5: Claydloam tas te. fe Se aes Se woe ee eee 302 55.7 0.0 1925 
Grainkeees |e 22 COs So ai ae eR ne 291 83.3 0.0 25.3 
Alfaliaeese Gravelly act noe nke sates He eee 147 24.8 0.0 1.8 
Grainne see | sea CO ee Ee ea aa et eee | 122 31.4 0.0 | 2.3 
Table XIX shows that over one-half of the water applied to grain 
and alfalfa upon clay loam soils is sometimes wasted, and that the 
average waste of the total quantity applied was 25.3 per cent for 
grain and 19.1 per cent for alfalfa. The above figures are based on 
the results from single fields, however, and irrigators should not be 
allowed to waste this percentage from their entire holdings. Irri- 
gated farms should be so laid out that as much as possible of the 
waste water may be caught up and used over again on one or more 
fields before it is finally allowed to be wasted from the farm. It is 
safe to assume that the average farm could be so laid out that the 
water would not waste directly off the farm from over one-fourth 
its area. Rather steep farms, however, of small area, would suffer 
a larger waste than large farms or those with flatter slopes. Under 
normal Idaho conditions it is believed that all water contracts should 
provide for a sufficient delivery over and above the actual water 
requirements of the soils and crops so that the irrigator could waste 
between 7.5 and 12.5 per cent of the quantity delivered to him and 
still retain sufficient for his crop needs. The fact that present 
economic conditions will not justify a farmer in eliminating all waste 
must not be overlooked when designing new projects, and the con- 
tracts should provide for a delivery somewhat in excess of the actual 
needs of the soil and crops. This is not a serious factor when a 
project as a whole is considered, for at least one-half of the quantity 
wasted by the individual farmer can usually be caught up and 
measured out to other consumers. 
DEEP PERCOLATION WASTE. 
That crops do not and can not utilize at the most more than 2.5 
acre-feet per annum and that they probably utilize and transpire 
far less than this amount has been proved by the many large yields 
that have been made in the Idaho investigation with comparatively 
small supplies of water, and may also be seen from the curves in 
figures 3 and 4. Much of the water applied in excess of 2 to 24 feet 
per acre in any region is lost through evaporation, surface waste, or 
deep percolation. With the more porous soils the loss from deep 
percolation beyond the reach of the plant roots is the greatest source 
bi ce aes 
SO VA ae aa haa 
