83 



acre of canyon bottom in August and a total of 47 acre-inches per 

 acre in the period July to October, inclusive. This amount ex- 

 ceeds water used by tules in a swamp at Victorville and is about 

 2 1/2 times the amount required by either saltgrass or Bermuda 

 grass where the water table was but 2 feet from the surface. 



Studies in Sacramento-San Joaquin Delta, Calif orn 



iai/ 



The Sacramento-San Joaquin Delta area in California differs 

 from the southern portion of the State in the comparative ease 

 with which water is secured for crop use. In the southern portion 

 water is scarce and ground water is found at depths beyond the 

 reach of plant roots. In the Delta, especially in the peat lands, 

 water is close to the surface, even invading the root zone, and 

 open water areas are numerous. Under these conditions tule and 

 cattail growth is encouraged and many areas, now considerably de- 

 creased in size by reclamation, support aquatic plants. Weeds 

 likewise are prolific because of high ground water and the oppor- 

 tunity of obtaining an ample water supply. In addition, a long 

 growing season and high summer temperatures increase transpiration 

 rates. As a result of these conditions wild growth often extracts 

 from the soil large quantities of water. 



Tules and cattails . --As in other sections of the State, 

 investigations have been carried on by the Division of Irrigation 

 in cooperation with the California State Division of Water Re- 

 sources to determine monthly and annual use of water by aquatic 

 and weed growth. Data on quantities of water consumed by tules 

 and cattails grown in exposed tanks at Clarksburg are given in 

 Table 19. The excessive monthly rate and the high annual total 

 should not be taken as actual consumptive use under normal condi- 

 tions of growth. Previous discussion has shown the fallacy of 

 attempting to determine consumptive use of water by plants grown 



ij Field work was conducted under the supervision of the late 

 0. V. P. Stout, Irrigation Engineer, Division of Irrigation, in 

 cooperation with Division of Water Resources, Department of Public 

 Works, State of California. 



