IRRIGATION REQUIREMENTS OF THE GREAT BASIN 39 
tities of water. When one considers, however, the value of irriga- 
tion water, the time required to irrigate, and the damage which the 
waste water resulting from overirrigation is likely to cause in water- 
logging soils and causing alkali to rise into the root zone, it is 
seldom that such a practice is justified from an economical point of 
view. Such a practice is also at variance with a wise public policy. 
In the Great Basin, for every acre that eventually is irrigated with 
the limited water supply at least 6 acres of arable land must remain 
dry and barren. In view of the abundance of arable land and the 
shortage of water, it has been deemed advisable to limit the use of 
water to the actual requirements for profitable crops. 
In a few cases the net requirements have been placed below this 
limit on account of the extreme scarcity of water in certain locali- 
ties coupled with the possibility of growing crops that require little 
water, providing the climate is suitable. To illustrate : Deciduous 
fruit trees, vines, corn, beans, millet, and sorghum may be grown suc- 
cessfully with the use of 35 to 50 per cent of the water required for 
alfalfa. 
Many who are familiar with the present methods of using water 
in the Great Basin will consider as too low the seasonal net require- 
ments given in the table. Such an opinion is well founded if the 
present wasteful methods of use are to continue and no further effort 
is made to store the flood waters. It will be noted that the figures 
given are based on an economical use, a regulated water supply and 
the reuse of waste water wherever feasible. If crops can be sup- 
plied with water at the time of need, from surface run-off, ground 
water, or storage reservoirs, and without undue waste, it is believed 
the conclusions reached in this bulletin will pave the way for the 
largest agricultural development possible with the extremely small 
available water supply. 
In the economical design of irrigation works it is of outstanding 
importance to know the largest quantity of water that will be re- 
quired during any monthly period of the irrigation season. As an 
aid to good practice in this respect, an estimate has been made, based 
on regulated stream flow, of the percentage of the total seasonal 
water requirements that is likely to be required in each month of 
the period of water deliver}^. These percentages for each subdivi- 
sion are given in the appendix in Table 6. 
USE OF WATER ON CROPS IN THE GREAT BASIN 
All the reliable records available pertaining to the measured use 
of water on crops in the Great Basin have been compiled and are 
herein appended in the form of tables. These tables give the sea- 
sonal use of water on plots and fields and the monthly use on other 
plots and fields. The results of use and duty of water experiments 
have been obtained from the following sources : 
(1) Unpublished reports on this subject prepared by members of 
the Division of Agricultural Engineering, Bureau of Public Koads, 
United States Department of Agriculture. 
(2) Unpublished reports of cooperative irrigation investigations. 
(3) Published reports of the Utah, Nevada, and Oregon agricul- 
tural experiment stations. 
