PROBLEMS FROM DEVELOPMENT 41 



in 5 or 10 years or longer. Development of these reservoirs for 

 perennial water supply must be on a trial-and-error basis in 

 the absence of hydrologic records covering many decades. The 

 annual draft must be less than the quantity replenishing the 

 reservoir in occasional wet years, because some of that quantity 

 should be held for use in years when pumping must be largely 

 from storage. 



Because of the variation in rate of recharge from year to 

 year, judgment as to whether wells are drawing more from a 

 reservoir than is being replenished should be based on records 

 for many years. In same desert basins, replenishment may oc- 

 cur so rarely and in such small quantities as to be considered 

 negligible. 



Sonoran Desert of Arizona and California. 5 In several 

 parts of southwestern Arizona and southeastern California, 

 the evidence of negligible recharge to ground-water res- 

 ervoirs is based in part on the reports of reconnaissances for 

 desert watering places. These are the basins in which there 

 are very few springs or other evidences of ground-water dis- 

 charge and in which the water table nearly everywhere is 

 far below the land surface. Precipitation over the drainage 

 basin is so scant that it could conceivably be dissipated en- 

 tirely by evapotranspiration from the soil zone, and it is 

 reasoned that if there were periodic accretions to the 

 ground-water reservoir, there would have been accumula- 

 tion during past decades and centuries that by now would 

 have filled it to a level where discharge could occur. 



For example, Ivanpah Valley, a closed basin in California 

 near the southern tip of Nevada, receives very little recharge 

 to its ground-water reservoir from the meager precipitation 



s References: Thompson, D. G., The Mojave Desert Region, U.S. Geol. Sur- 

 vey Water Supply Paper 598, p. 608, 1929. 

 Barr, A. T., and E. C. Sandberg, "The Part Water Plays in Min- 

 ing," New Cornelia Branch, Phelps-Dodge Corp., Ajo, Ariz., 

 Mimeo. rept., 1941, 16 pp. 

 "Ground Water in Bouse Valley, Ariz.," U.S. Geol. Survey rept., 

 in preparation. 



