140 CONSERVATION OF GROUND WATER 



courses of the Ohio and Allegheny Rivers. Most of the wells 

 are so situated that there is adequate replenishment by river 

 infiltration or by local precipitation, and there arc many 

 excellent sites for development of additional supplies along 

 both watercourses. 



Serious troubles with ground-water supply have devel- 

 oped in two small areas in Pittsburgh. One of these is the 

 "Golden Triangle" — the 0.4-square-mile area of flood plain 

 at the junction of the Allegheny and Monongahela Rivers, 

 which is Pittsburgh's downtown business district. More 

 than 12 million gallons a day is pumped from 65 wells in 

 the triangle each summer, more than half of which is for 

 air conditioning. Water levels in some wells are lowered to 

 within a few feet of the bedrock at the peak of the heaviest 

 demand. Hydrologic studies have shown the reason for this 

 condition. The ground-water reservoir under the triangle 

 is not only of limited areal extent but also of limited thick- 

 ness, generally less than 40 feet. Thus, it has only limited 

 storage to meet the heavy draft for air conditioning. Re- 

 charge occurs chiefly from the streams which, except during 

 high flow, are held at constant stage by a series of locks and 

 dams. During periods of heaviest pumping the rate of with- 

 drawal exceeds the rate of recharge, and water levels are 

 lowered as much as 12 feet in unpumped wells and even 

 more in production wells. The streams replenish this water 

 during winter and spring. 



The other problem area is near the upstream end of 

 Neville Island, where large quantities of water are pumped 

 for the north boroughs and for several large industries. 

 Here, too, seasonal draft appears to be in excess of imme- 

 diate replenishment, and much of the water is pumped 

 temporarily from storage. 



The problems of these areas result from the increasing 

 demand for ground water and from development in igno- 

 rance of the capabilities for replenishment of the water 

 taken from the ground-water reservoir. It is likely that the 

 watercourses in the Pittsburgh area can yield far more 



