PROBLEMS FROM DEVELOPMENT 67 



diverting part of its share to other valleys, and the ultimate 

 quantity available for Las Vegas Valley may be about 

 200,000 acre-feet. 



For many ground-water reservoirs, it has been possible to 

 reduce the disparity between draft and natural replenishment 

 by increasing the replenishment artificially, which is a more 

 desirable solution to the problem than the alternative of 

 restricting or reducing the withdrawal of ground water. Sev- 

 eral of California's coastal valleys are traversed by streams 

 responsible for much of the ground-water replenishment but 

 which also discharge considerable quantities of water into the 

 ocean. Since 1934, the Santa Clara Valley Conservation 

 District has constructed storage dams and percolating works 

 to divert surplus stream water into the ground-water reservoir 

 of Santa Clara Valley (page 53). Similarly, spreading basins 

 along the Santa Clara River in southern California have put 

 nearly 10,000 acre-feet of water underground for the Oxnard 

 Plain, thus reducing the overdraft. The Los Angeles County 

 Flood Control District has constructed diversion works and 

 spreading grounds for artificial recharge of ground-water res- 

 ervoirs from water held back by the flood-control dams con- 

 structed by the Corps of Engineers and by the Los Angeles 

 County Flood Control District. And comprehensive plans 

 have been completed for utilization of surplus flows of the 

 Salinas River to relieve present conditions of overdraft and 

 salt-water encroachment in the ground-water reservoir of 

 Salinas Valley. It may be feasible to use winter stream sur- 

 pluses to relieve overdraft in several other California valleys, 

 including Livermore Valley, Santa Maria Valley, and the Santa 

 Ynez Valley. 



The effluent from sewage-treatment plants has been utilized 

 by several western cities for irrigation, and some reclaimed 

 water is returned by percolation to ground-water reservoirs. 

 In Denver, Colorado, about two-thirds of the water used for 

 municipal supply eventually reaches the sewage-treatment 

 plant; the effluent is discharged to the South Platte River, 



