WHAT'S HAPPENING TO WATER? — ROBINOVE 381 



of Phoenix and Tucson. Nevertheless, a stable water supply is needed 

 for those who live and work in the Navajo country. Few streams 

 are perennial — the Colorado and San Juan Rivers on the west and 

 north sides of the Navajo country are the principal exceptions, but 

 water from these generally is not available because the streams are 

 deeply entrenched in canyons and the water contains large amounts 

 of sediment. The meager supplies on the reservation come from small 

 and undependable reservoirs on intermittent streams and deep but 

 dependable wells. On an average, only about 10 gallons of water per 

 day is available for human consumption (U.S. House of Representa- 

 tives, 1953, p. 126). A larger and more dependable water supply can 

 be assured only by a program of storage of runoff, promotion of the 

 growth of plants that would use less water or be of more economic 

 value than the present native species, and use of the ground-water 

 reservoirs to the maximum capability, if such is economically feasible. 

 Such a program would be expensive and would require more informa- 

 tion on the Navajo country than is now available. 



The second major water problem is that of variability. The avail- 

 able water supply may be less than the demand during drought years 

 and greater than the demand during wet years. The average water 

 supply may be able to meet the average demands, but this statement 

 is small consolation to a user of water who must face several years of 

 drought during which he cannot get enough water to meet his needs. 

 This problem gives rise to the often asked question "Is our total water 

 supply decreasing?" The answer to this is "No!" We may have less 

 water at a certain place at a particular time but at other times we may 

 have more water than we can use. Thus, droughts have been of serious 

 proportions in the Central Plains in the 1930's and in a large part of 

 the country in the 1950's, but at other times these regions have had 

 surpluses of water. 



Water supplies vary throughout a single year also. Irrigation in 

 the West demands large and dependable water supplies during the 

 growing season, but the natural stream runoff varies greatly during 

 that time. Storage of surface water in reservoirs to regulate the flow 

 for irrigation, together with the use of stored ground water, can even 

 out the usable supply and allow its release when needed. 



The distribution of the water supply is the third problem of major 

 importance. The distribution problem means that the supply exceeds 

 the demand in one part of a region and is less than the demand in 

 another. For example, northern California has large supplies of 

 water and the demand for water is small ; southern California, in con- 

 trast, has a limited supply but its large, ever-expanding population 

 and industry need ever-increasing amounts of water. 



The Los Angeles River furnished the municipal water supply for 

 the city of Los Angeles from the founding of the city in 1781 until 



