PROBLEMS FROM DEVELOPMENT 147 



creasing municipal requirements, Canton in 1947 turned 

 to the small west branch of Nimishillen Creek, where gravel 

 strata near the surface are readily recharged by the creek 

 but have relatively small storage capacity. Under this gravel 

 and separated from it by clay is another gravel stratum, with 

 large storage capacity but slow natural recharge. The city 

 uses both aquifers for its water supply: the upper aquifer 

 yields as much as 18 million gallons a day to the lower gravel 

 through recharge wells constructed for the express purpose, 

 and 10 million gallons a day or more can be pumped peren- 

 nially from the deeper reservoir. 



WHERE THE SURFACE WATER IS UNSUITABLE FOR USE 



The technique of inducing infiltration from a river is gen- 

 erally to locate wells close to the riverbank, where the distance 

 traveled by water in rock materials is minimum, and the hy- 

 draulic gradient encourages rapid transmission. Of course if 

 the river carries brackish or otherwise unsuitable water, wells 

 close to the river will draw in that water. Wells at Wilming- 

 ton, N.C., Fort Myers, Fla., and New Haven and Bridgeport, 

 Conn., have pumped water that has infiltrated from the tidal 

 portions of nearby streams. In several of these places the prob- 

 lem has been solved by developing wells at greater distances 

 from the streams. The problems of brackish-water infiltration 

 from a river are typified by the experiences of Mobile, Ala. 



Mobile, Ala. 71 This city obtains its municipal water sup- 

 ply from small tributaries of the Mobile River, and ground 

 water is used chiefly for air conditioning. In the downtown 

 district as much as 2 million gallons a day has been pumped 

 from wells 25 to 90 feet deep in the alluvium along the water- 

 course of the Mobile River. Under natural conditions this 

 alluvium receives sufficient replenishment by downward 

 percolation of precipitation that the water table is generally 

 higher than the river level, and ground water moves toward 

 the stream. At flood stages, however, the river water moves 



7i Reference: Peterson, C. G. B., Ground-water Investigation in the Mobile 

 Area, Alabama, Geol. Survey Ala. Bull. 58, 1947, 32 pp. 



