INTRODUCTION 5 



is generally inadequate for the needs of man. Some have an 

 area of a hundred square miles or less; others may embrace 

 several counties or extend across state or international boun- 

 daries (see Plate II). Generally, the ground-water users are 

 aware that they are using more than the perennial supply and 

 that the supply will be exhausted unless action is taken. Cor- 

 rective measures already applied in certain areas include pre- 

 vention of waste, prorata reduction of pumping from all wells, 

 prohibition of further development, reclaiming of used water, 

 artificial ground-water replenishment by surplus stream 

 water, and importation of water from other areas. 



Not all the ground-water reservoirs in the arid regions are 

 overdeveloped. Many have potentialities for additional devel- 

 opment, though not because they are more favored in replen- 

 ishment than the fully developed or overdeveloped reservoirs. 

 Rather they are less favored by people, for lack of fertile land 

 or mineral resources, agreeable climate, or for other reasons. 

 The potentialities of most of these undeveloped reservoirs 

 are not great, due to the low rates of precipitation and ground- 

 water replenishment that prevail throughout the arid lands. 

 In fact, in some areas practically uninhabited at the end of 

 World War II, the ground-water reservoirs now appear to be 

 overdeveloped, after only a few years of intensive well drilling 

 and pumping. 



A few ground-water reservoirs receive very little natural 

 replenishment. Some are in deserts where replenishment oc- 

 curs only after exceptional rainstorms that may be several 

 years apart; others are almost completely sealed off by clay or 

 other material that impedes entry of water from precipitation 

 or from other sources. The water in these reservoirs can hardly 

 be classed as a renewable resource. Where the quantity stored 

 in them is large, there is a real problem involved in develop- 

 ment: should the water be extracted for maximum benefit of 

 the present generation, as minerals and other nonrenewable 

 resources are mined, or should the pumping be limited to the 

 negligible quantity that can be supplied perennially? 



The pipeline problems are due chiefly to the slow rate of 



