148 CONSERVATION OF GROUND WATER 



into the alluvium, and because the stream is tidal and brack- 

 ish, ground water has always been somewhat saline within 

 about 800 feet of the stream channel. The pumping for air 

 conditioning has lowered the water table below river level 

 and has induced river infiltration. In downtown Mobile, 

 saline water has been detected as much as 2,300 feet from the 

 channel, and the salinity has increased in one well from 

 950 parts per million of chloride in 1942 to 2,200 parts per 

 million in 1945. 



A deep artesian reservoir, 800 feet below the surface, 

 yields water by artesian flow with a temperature about 6 

 degrees higher than the water from the shallow aquifer. 

 There is relatively little draft from this aquifer, and arte- 

 sian pressures have not declined in recent years. Wherever 

 the salinity in the shallow aquifer has made the water un- 

 suitable for air conditioning, there are the alternatives of 

 drilling other shallow wells farther from the river, or using 

 the warmer water from the deeper aquifer or from the Mo- 

 bile public supply. 



About 2 miles north of Mobile some 13 million gallons 

 a day is pumped from shallow and deep wells for manufac- 

 ture of paper. Salt-water encroachment there has been a 

 problem only in the shallow wells nearest the river. 



Rivers may be contaminated at many places other than in 

 the coastal areas where ocean water moves upstream. Streams 

 constitute a common means of disposal for the mineral matter 

 dissolved by water in their drainage basins. Those draining 

 areas of saline or gypsiferous rocks are likely to carry much 

 dissolved mineral matter, as for instance the Cimarron River 

 and Salt Fork of the Arkansas in Oklahoma, where both the 

 streams and ground-water reservoirs of the watercourse carry 

 saline water. As another example, El Paso, Tex., along the 

 watercourse of the Rio Grande, could obtain an ample sup- 

 ply of water from the ground-water reservoir recharged from 

 the river. Both the stream water and shallow ground water 

 are highly mineralized, however, owing in part to return flows 



