36 CONSERVATION OF GROUND WATER 



Pipeline problems may develop in any ground-water res- 

 ervoir, due to inability of the water to move rapidly enough 

 through the aquifer to meet the demand of specific wells or 

 well fields. The problem is analogous to that of distribution 

 systems afflicted with inadequate pipelines or distribution 

 mains, which will give trouble even where the total supply of 

 water is adequate. In ground-water reservoirs, as in water- 

 supply systems, there are also problems of loss by wastage or 

 leakage and problems of contamination of the supply by pol- 

 luted water. 



The watercourse problems are those where the ground- 

 water and surface-water resources are so intimately related that 

 they must be considered a single hydrologic unit. 



Reservoir Problems 



reservoirs in which natural replenishment is 

 inadequate for current uses 



The areas of serious sxound-water shortage are those in 

 which wells, year after year, draw water from the ground- 

 water reservoirs in excess of the annual replenishment. If a 

 lake or surface reservoir were drawn upon similarly, the effect 

 would soon be visible in the lowered lake levels and eventual 

 draining of the entire reservoir. The effects are not so readily 

 apparent in a ground-water reservoir, because the total water 

 stored in it may be enough to supply the wells for several 

 decades, but the removal of that water will be evidenced by 

 progressive lowering of water levels in wells throughout the 

 reservoir area. 



The ground-water reservoirs in which the draft in 1949 is 

 considered to be in excess of average natural replenishment 

 are shown on Plate II. Perennial overdraft is indicated in more 

 than 30 important ground-water reservoirs, but in several of 

 these the overdraft has been reduced by corrective measures. 

 Nearly all these are in the arid regions (see Figs. 1 to 3) where 

 all water supplies are deficient. It is altogether possible, in 



