in Section 226 (e) of the Water Code, which states that the depart- 

 ment may "Conduct investigations of the rate of use of water for 

 various purposes and considering various soil conditions." 



Objective 

 The overall objective of the vegetative water use studies 

 is to Investigate and establish a means whereby the department can 

 accurately determine long-term monthly and seasonal irrigation re- 

 quirements and evapotranspiration for the principal crops grown 

 within the various agricultural zones throughout California. To 

 accomplish this broad objective, the vegetative water use studies 

 are divided into three principal programs; namely, agroclimatic 

 monitoring, evapotranspiration measurement and correlation, and 

 irrigation requirement determination. The first two of these pro- 

 grams are designed to accomplish the following primary objectives: 

 first, to collect agroclimatic data in major agricultural areas to 

 provide a means of dividing the State into agroclimatic zones of 

 potential water use, and for estimating evapotranspiration within 

 those zones; and second, to test, on a statewide basis, certain 

 procedures suggested by fundamental research by the University of 

 California and other agencies, regarding correlation of evapotranspi- 

 ration with various types of agroclimatic data. The objective of 

 the third program is to correlate measured values of total applied 

 water with evapotranspiration. These data will make possible the 

 calculation of other pertinent water use information, such as ir- 

 rigation efficiencies and drainage requirements. Very little has 

 been accomplished on the third program to date, 



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