PROBLEMS FROM DEVELOPMENT 97 



Estimated Input and Outflow of San Fernando Ground-water 

 Basin, 1943 (continued) 



Outflow Acre-feet 



Pumped or developed by city of Los Angeles 55,700 



Pumped or developed by other cities 27,800 



Pumped or developed by ranches, factories, and motion-picture 



companies 10,000 



Flow of rising waters past Narrows, Los Angeles River 35,000 



Total outflow 128,500 



Precipitation in the years 1936 to 1943 averaged about 40 

 per cent above normal in the drainage basin, and the ground 

 water stored in San Fernando Valley was increased consider- 

 ably. In representative wells, the water levels in 1944 were 

 25 to 50 feet higher than in 1931. The increased storage was 

 a valuable addition to the resources of the region, but the 

 effects were detrimental in a few places. In some of the lower 

 parts of San Fernando Valley, the water table rose to a posi- 

 tion so close to the land surface that some lands were water- 

 logged and basements flooded. Following a survey of this 

 situation in 1945 it was recommended that detailed studies 

 be made to determine the best methods of control of the 

 water table — whether by pumping or drainage canals or 

 other means — which would permit maximum use of the 

 valley's facilities for underground storage and yet would 

 cause minimum inconvenience in the lower part of the 

 valley. 



Development of many ground-water reservoirs has already 

 resulted in conflicts between the ground-water users and the 

 holders of surface-water rights. Wherever a ground-water res- 

 ervoir discharges into a stream, or vice versa, the utilization 

 of water from that reservoir is likely to modify the natural 

 pattern of stream flow. As development of these reservoirs 

 progresses toward full utilization, the number of conflicts will 

 inevitably increase. These problems are especially numerous 

 along watercourses, where ground water and surface water 

 are intimately related, and are discussed on pages 136-160. 



