120 



Saltgrass . --Consumptive use of water by saltgrass grown 

 artificially in large tanks in Owens Valley was determined for 

 various depths to water table. Evaporation from water and from 

 moist soil surfaces was likewise determined. As a result of pre- 

 liminary investigations six tanks were used for growths of salt- 

 grass sod. In these tanks ground water remained fairly constant 

 at predetermined depths except where it was so near the surface 

 that there was a high rate of consumptive use. In the tank in 

 which the water table was theoretically about 1 foot below the 

 surface, the grass withdrew water more rapidly than it could be 

 supplied from the connected reservoir tank, so that the water 

 table dropped from near the 1-foot level in the winter months to 

 below 2 feet in the summer. 



The investigation disclosed a diminishing rate of consump- 

 tive use as depth to ground water increased, in practically a 

 straight-line ratio. Reference to Table 35 shows the monthly and 

 annual use of water by saltgrass for various depths to water table, 

 ranging from an annual maximum of 48.80 inches where average depth 

 to water table was 18 inches to an annual minimum of 13.43 inches 

 where average depth to water table was 59 inches. Observations in 

 the Owens Valley showed little saltgrass in localities where 

 groiind water exceeded 8 feet, indicating inability of the roots to 

 function beyond this depth. It does not follow that this is the 

 limit in all saltgrass fields. The maximum depth observed in 

 southern California was 11 feet in clay soil. 



Estimated Water Supplies 



As a result of this investigation, Lee made estimates of 

 evaporation and consumptive use of water losses for 54-59 square 

 miles of high ground-water alkali and saltgrass lands, as shown 

 in Table 36, and converted the consumptive use into equivalent 

 stream flow. The average rate of discharge for the 54.59 square 

 miles where depth to water did not exceed 8 feet was equivalent 

 to a continuous flow of 2 cubic feet per second per square mile. 



