132 CONSERVATION OF GROUND WATER 



In the South heavy pumping at several coastal cities has re- 

 sulted in development of cones of depression which extend 

 below sea level. At Savannah and Brunswick in Georgia, and 

 Fernandina, Miami, and Tampa in Florida, the ground-water 

 reservoir is in permeable limestone; at Pensacola, Fla., and 

 Gulfport, Miss., water is yielded by permeable sand and 

 gravel. Salt water has moved into the ground-water reservoirs 

 at Miami (see page 195) and at Tampa and St. Petersburg. At 

 Pensacola, too, increasing; salt content has been noted at some 



77 o 



wells, which was probably drawn in either from Pensacola 

 Bay or Bayou Chico. At the other places there is as yet no evi- 

 dence that saline waters are entering- the fresh-w r ater reservoir. 

 However, wherever the cone of depression drops below 

 sea level, there is some cause for fear that the reversed gra- 

 dient may eventually induce inflow of saline water from the 

 ocean. 



Savannah, Ga. 60 Pumpage of artesian water in Savannah 

 increased from 38 million gallons a day in 1942 to 47 million 

 gallons a day in 1945 and is probably of the order of 50 mil- 

 lion gallons now. Prior to 1880 the piezometric surface was 

 about 35 feet above sea level in Savannah, sufficient to yield 

 water by artesian flow. Pumping, however, has lowered 

 water levels as much as 100 feet, so that they are now more 

 than 50 feet below sea level in some wells. The cone of de- 

 pression formed by pumping extends more than 20 miles in 

 all directions. 



The source of this water is the highly permeable Ocala 

 limestone, 750 feet thick and with its top 200 feet below sea 

 level at Savannah. This limestone is recharged in outcrop 

 areas 70 or more miles northwest of Savannah. Under 

 natural conditions water is discharged into the Savannah 

 River from this limestone about 40 miles northwest of 

 Savannah. Tests have indicated that the Savannah cone of 

 depression has already extended far enough so that pumping 



60 Reference: Warren, M. A., Artesian Water in Southeastern Georgia, 

 Georgia Geol. Survey Bull. 49, 1944, 140 pp. 



