72 CONSERVATION OF GROUND WATER 



of about 3 feet per year between 1921 and 1938, and more 

 than 5 feet per year subsequently; the net lowering in the 

 area of heaviest pumping has been more than 150 feet since 

 1926. In the Lindsay area the mean depth to water in wells 

 increased from 55 feet in 1921 to 135 feet in 1945, and to 

 more than 150 feet in recent years; wells near the center of 

 the cone of depression are pumping water of increasing 

 salinity. 



Development in other places has resulted in raising the 

 water table, which in some areas has resulted in alkali ac- 

 cumulation and abandonment of farms and in others has 

 been solved by drainage (page 197). And some areas in the 

 lower parts of the Tulare Lake basin are afflicted with more 

 complex problems: pumpage from deep artesian wells is 

 depleting the ground-water storage, and the irrigated land 

 above has such poor drainage that the water table is un- 

 comfortably high. 



The success of the Central Valley Project will be depend- 

 ent partly upon utilization of the ground-water reservoir 

 of San Joaquin Valley for storage of imported waters. These 

 waters would perform a double duty if cropped lands could 

 be irrigated excessively, with resulting percolation to the 

 ground-water reservoir. The prevailing fine-textured soils 

 of the valley interpose one difficulty here, because of the low 

 natural rates of percolation. The percolation through tight 

 soils has been increased substantially by application of 

 cotton-gin trash; research is continuing to determine the 

 specific chemical or biological property of the trash that 

 causes increased infiltration, in the hope that synthetic 

 manufacture and widespread application may be possible. 

 But in many places the aquifers are at depths of several 

 hundred feet; getting water through the surficial zone is 

 only the first step in recharging those aquifers. 



There is a further problem of replenishing the water in 

 artesian aquifers that are important sources of the water 

 pumped from wells. Flowing wells could once be obtained 



