46 CONSERVATION OF GROUND WATER 



sive rainfall, recharge to the °round-water reservoir is in- 

 hibited in most of the so-called "hard lands" by widespread 

 clay subsoils or by cemented caliche zones, and the water 

 from precipitation is dissipated instead by evaporation from 

 the soil zone and from numerous ponds and lakes that form 

 in depressions, or to a small extent by stream flow. The 

 principal areas of recharge are sand hills and small areas 

 of sandy soil. 



It is estimated that because of this combination of climatic 

 and ^eolooric factors, recharge to the ground- water reservoir 

 is of the order of 50,000 acre-feet a year — about 4 per cent of 

 the current rate of pumping. Rainfall upon the High Plains 

 is the only source of water in the underlying sands and 

 gravels. There is no possibility of natural recharge from the 

 Rocky Mountains, the Pecos River, or the Canadian River. 



The natural discharge of ground water from springs and 

 seeps along the east border of the High Plains — perhaps 

 50,000 acre-feet a year — has not yet shown any obvious 

 diminution as a result of the great withdrawals of water 

 from wells in recent years. Thus, practically all the water 

 pumped to date has been from storage within the aquifer. 

 The total water still in storage is estimated to be of the order 

 of 150 million acre-feet, of which nearly two-thirds is be- 

 lieved to be within 200 feet of the land surface. It is evident 

 that the storage would be sufficient for many decades of 

 withdrawal at present rates, if the wells were properly dis- 

 tributed over the High Plains. 



If the ground-water reservoir were emptied, it would take 

 some 30 centuries to refill at present-estimated rates of 

 natural recharge. But the present development has not been 

 planned with a view toward scientific extraction of water 

 over a period of several decades. Pumping from 1938 to 

 1949 lowered the water table more than 10 feet over more 

 than half of the 6,700-square-mile pumping district in 

 Texas; concentrated draft near Lubbock and Plainview 

 caused a decline of more than 40 feet in an area of 10 square 

 miles. In these areas of concentrated draft, the storage in the 



