56 CONSERVATION OF GROUND WATER 



Los Angeles Coastal Plain, Calif. 13 The Los Angeles 

 Coastal Plain receives the outflow from three inland val- 

 leys — San Fernando, San Gabriel, and Upper Santa Ana. 

 The ground-water reservoir is quite generally confined be- 

 neath impermeable material, except in the relatively small 

 intake areas adjoining the passes from the inland valleys. 

 Ground water is recharged in those intake areas and under 

 natural conditions moves westward toward the ocean. How- 

 ever, this movement is seriously impeded along the New- 

 port-Inglewood barrier (produced by faulting and uplift). 

 The West Basin — extending from Long Beach to Santa 

 Monica — lies beyond that barrier. 



Pumpage from walls in the West Basin is currently about 

 90,000 acre-feet a year. The replenishment by underflow 

 across the Newport-Inglewood barrier would be far less 

 than this amount even under the conditions preceding de- 

 velopment. In recent years more than 300,000 acre-feet of 

 water has been pumped annually in the inner part of the 

 coastal plain, and water levels there have been drawn down 

 about in the same amount as those in the West Basin. Al- 

 though replenishment across the barrier has remained nearly 

 constant, much of the pumpage in the West Basin has been 

 from storage, and water levels have declined until they are 

 below sea level in most of the basin and more than 70 feet 

 below sea level in some areas. Because of the landward gra- 

 dient that has been developed, ocean water has moved as 

 much as 2 miles inland from the coast, along a 12-mile strip 

 that includes Manhattan Beach and Redondo Beach. 



It is evident that the problem of overdraft and salt-water 

 contamination cannot be solved within the West Basin 

 alone, because replenishment is governed by conditions in 

 the rest of the Coastal Plain. Complete cessation of pump- 

 age within the West Basin would result in movement of sea 



13 Reference: Poland, J. F., A. A. Garrett, and Allen Sinnott, "Geology, 

 Hydrology, and Chemical Character of the Ground Waters 

 in the Torrance-Santa Monica Area, Los Angeles County, 

 Calif.," U.S. Geol. Survey, Duplicated rept., 1948, 472 pp. 



