Beneficial Use of Water 
in Arid Lands 
JOHN H. DORROH, JR. 
Soil Conservation Service, 
United States Department of Agriculture 
Albuquerque, New Mexico 
During the past several years the Soil Conservation Service has 
studied the characteristic precipitation and water yields of Ari- 
zona, Colorado, New Mexico, and Utah in an attempt to deter- 
mine: (1) what the average annual precipitation is; (2) what part 
of this original supply is available for irrigation, domestic, and 
other uses; (3) what watershed or climatic factors are predom- 
inant in the production of water yields; and (4) what may be done 
to reduce losses of water to non-beneficial use. 
During the course of the study, isohyetal and water yield maps 
of the four states were developed on a scale of 1: 500,000 to permit 
reasonable delineations of usual amounts of precipitation and 
subsequent water yields throughout the four-state area. Weighted 
amounts of precipitation and the apparent total yield of water to 
downstream users were then determined. The annual precipitation 
varied from less than 4 to about 60 inches, and water yields from 
less than one-tenth inch to more than 30 inches. The figures for 
water yield do not take into account flow into or out of the four- 
state area; they are merely map measurements. However, they are 
considered representative of existing conditions. 
Although the four states were covered in their entirety, the 
following discussion will be confined to those portions with an 
annual precipitation of 18 inches or less. These, we believe, en- 
compass the arid zones. 
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