84 BULLETIN 1026, TJ. S. DEPARTMENT OF AGRICULTURE. 
applied is light enough to prevent an undue loss by deep percolation. 
The head used should be governed by the conditions above and the 
soil. Large heads should be used when possible, as they save both 
time and water if handled properly. 
The run-off from the lower end of the field averages 6 per cent 
of the amount applied. This is a very low average, but there are 
many farms where much improvement could be made along this 
line. 
The average number of irrigations applied on the fields under 
investigation ranged from 1.21 for wheat to 3.79 for potatoes. 
The average head used by one irrigator ranged from a minimum 
of 1.85 second-feet for sugar beets to a maximum of 2.59 second-feet 
for alfalfa. 
The number of acres irrigated per day by one person ranged from 
an average of 4.45 for barley to 6.78 for potatoes. Beans were in 
an entirely different class with an average of 15.63 acres per day 
per man. 
The average duty in acre-feet per acre, measured at the head of 
the farm lateral, was : Alfalfa, 2.57; wheat, 1.04; oats, 1.35; barley, 
1.19; sugar beets, 1.86; potatoes, 2.20; beans, 0.69. 
Keservoirs are by far the most important factor govering the good 
use of water in the valley. By their use water is made available 
when and only when needed. Without them an entirely different 
type of development would have resulted in the valley. 
The large number of reservoirs was made possible by natural 
basins which could be developed with a minimum of trouble and 
expense. For thirteen of these reservoirs with an aggregate capac- 
ity of 72,000 acre-feet the average cost of development was $6.75 
per acre-foot of capacity. 
The majority of reservoir dams are low earth fills, and slopes 
are protected against erosion by rock riprap or concrete pavements. 
For these comparatively short slopes both types of protection have 
given satisfaction. 
Gate wells are now placed in the dam at the top of the inner 
slope. Locating them either at the upper or lower end of the 
outlet was found to be unsatisfactory and at times dangerous. 
Outlet conduits are generally of stone or concrete and are often 
in cuts through the rim of the natural basin forming the bottom of 
the reservoir. 
The aggregate capacity of reservoirs with decreed rights from 
the main river is now in excess of the normal available supply and 
further new projects of that type are not feasible. Storage develop- 
ment in the future should be along the line of flood-control reser- 
voirs high up on the stream by which the flow of the stream below 
could be made to conform to actual current irrigation requirements, 
