INTRODUCTION 11 



Past development of ground-water reservoirs has generally 

 been in ignorance of their potentialities and especially their 

 limitations. Realization of the limits of surface supplies came 

 early, particularly in the arid states, where deficient precipita- 

 tion sets a low ceiling on all water supplies. The limitations 

 in ground-water supplies in those regions became apparent 

 much later and are just beginning to be apparent in humid 

 regions. 



Most of the scientific analysis of ground-water problems to 

 date has been restricted to the ground-water phase of the hy- 

 drologic cycle, and recommendations for optimum utilization 

 have been based largely on the rate of natural replenishment. 

 In many ground-water reservoirs this quantity is large enough 

 to permit utilization of far more water than is currently de- 

 veloped. But in many places, if we knew enough, it might be 

 possible to utilize ground-water reservoirs like surface reser- 

 voirs, storing water in them by artificial recharge, and ma- 

 nipulating that storage to best advantage, rather than merely 

 drawing out what nature puts in. Successful manipulation of 

 ground-water storage will require full knowledge of ground- 

 water reservoirs as components of the hydrologic cycle, and, 

 therefore, a comprehensive analysis of the meteorology of the 

 area, as well as the hydrology of soil moisture, ground water, 

 and surface water. Studies in many areas have already shown 

 the intimate relation of ground water to surface water, and of 

 both to infiltration and soil moisture. 



The recharge areas are of critical importance in the artificial 

 replenishment of ground-water reservoirs. Effective treatment 

 of them may well require many of the basic practices which 

 have been successful in soil and soil-water conservation. Wher- 

 ever replenishment of ground water is the principal objec- 

 tive, rather than an incidental benefit of the program, there 

 should be assurance that the ground-water supplies are actu- 

 ally being increased. Many ground-water reservoirs have been 

 successfully recharged artificially by various methods. For the 

 majority of reservoirs considerable scientific investigation is 

 needed before a workable program of artificial recharge can 



