CHAPTER I, INTRODUCTION 



This report presents data on vegetative consumptive use 

 of water, or evapotransplratlon, together with certain Interrela- 

 tionships with agricultural climatic factors Influencing such use. 

 The findings summarized cover the period 195^-1960, and represent 

 a large quantity of Individual measurements of evapotransplratlon 

 and related agricultural climatic data. The measurements of evapo- 

 transplratlon represent scores of soil samples, neutron probe read- 

 ings, and evapotranspirK)meter measurements of Irrigated alfalfa, 

 pasture, plums, cotton, and grass crops. Agricultural climatic or 

 agrocllmatlc data are likewise summarized from a large number of 

 measurements of evaporation from pans and atmometers. Certain other 

 agrocllmatlc data, such as measurements of solar radiation and rela- 

 tive humidity, were collected at a few stations. These data have 

 not been analyzed as yet, and will be reported in later publications, 



Need for Vegetative Water Use Studies 

 Historically, irrigated agriculture has been the largest 

 user of our developed water resources. This condition probably 

 will continue indefinitely. The Department of Water Resources, 

 hereinafter referred to as the department, and its predecessor 

 agencies, have made many measurements of water deliveries for agri- 

 cultural uses with regard to water right adjudication. However, 

 for broad planning purposes the department has relied largely upon 



