empirical methods for estimating seasonal values of evapotransplra- 

 tion or consumptive use for various crops. State Water Resources 

 Board Bulletin No, 2, "Water Utilization and Requirements of Cali- 

 fornia, 1955/' has been the primary source for such estimates. 



As more complex and costly water development facilities 

 are contemplated, more accurate values for irrigation requirements 

 and evapotranspiration v/ill be needed. The location and sizing of 

 reservoirs, distribution systems, and final disposal or drainage 

 systems are dependent upon accurate estimates of at least monthly 

 values of irrigation requirements and evapotranspiration for various 

 kinds of vegetation. Accurate irrigation requirements and evapo- 

 transpiration values are also important in planning for the con- 

 junctive operation of ground water reservoirs, the reclamation of 

 salt-affected lands, and in the maintenance of a favorable salt 

 balance within agricultural soils. Moreover, as water costs rise, 

 more accurate knowledge of evapotranspiration rates will become of 

 increasing importance in order to achieve greater efficiencies in 

 irrigation practices. 



Authorization 

 Estimates of evapotranspiration and irrigation require- 

 ments have long been a part of water development investigations, as 

 conducted by the department and its predecessor agencies. The preS' 

 ent program, designed to provide more accurate data on rates of 

 evapotranspiration, was initiated in July 195^ and broadened in 

 1959. pursuant to Senate Bill 43^, 1959 Legislative Session. 

 Specific authorization for conducting these studies is set forth 



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