CHAPTER III. EVAPOTRANSPIRATION MEASUREMENT 



The objective of the evapotransplration measurement and 

 correlation program Is to provide a more accurate basis for pre- 

 dicting evapotransplration for the major crops In the various agri- 

 cultural areas of the State. This is to be accomplished through 

 measurements of evapotransplration of various crops at several in- 

 land locations having different climatic conditions, and correlating 

 with the evaporative demand, as measured by evaporation pans and 

 atmometers. This chapter discusses the techniques and procedures 

 utilized in the measurement of evapotransplration, and changes that 

 have occurred during the development of the study. In Chapter IV 

 the correlation of the evapotransplration with pan and atmometer 

 evaporation data will be discussed and analyzed. 



The principal evapotransplration stations are located 

 near Bakersfield in the southern San Joaquin Valley and near Al- 

 turas and Fall River Mills in mountain valleys of the Sacramento 

 River Basin. Plate 2, entitled "General Location of Evapotranspl- 

 ration Stations, 1955-1960," shows the location, type, and status 

 of each station. More detailed information is given in Tables A-4 

 and A-5 of Appendix A, Measurements were made primarily on alfalfa 

 and grass, which are grown universally throughout the State. As 

 plant and soil moisture conditions affect evapotransplration rates, 

 evaluation of these factors is also an essential part of evapo- 

 transplration measurement. 



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