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A 1945 report is a comprehensive compilation of data that had been published or made available from public and private files as well as unpublished findings pertaining to agricultural crops common to California with a focus on the practical economic importance of this data in determining water supplies for and their uses in irrigation.


This 1945 report addresses the issue of water being the limiting factor in the expansion of irrigated areas. The increasing cost of new projects not only approached the capital values that newly irrigated lands might profitably support but in many cases exceeded them and other benefits were evaluated to justify construction. Conservation of existing water supplies was therefore of the first importance in the economy of the irrigated west. Savings in irrigation seldom exist where water was plentiful but where it was scarce conserving methods were the rule, wasteful practices were avoided, and water was carefully applied. It was axiomatic that the most economical use prevailed where there was a diminishing supply and water was high priced. Such conditions prevailed in parts of California.

In the report irrigation data available throughout the State was divided into three groups. First, irrigation requirements for some of the principal crops have been determined through experimental studies by State and Government agencies, frequently in cooperation with the Division of Irrigation, Soil Conservation Service. The second group included information on plant use of water as measured by soil moisture studies in determination of consumptive use or the transpiration use of water by crops. The third group of data included records of depths of water applied in ordinary irrigation practice, estimated water requirements by engineers, appraisers and experienced water administrators. For purpose of discussion, California was divided into six subdivisions, as follows: 1) South Pacific Basin, 2) Great Basin Desert Area, 3) San Joaquin Valley, 4) Sacramento-San Joaquin Delta, 5) Sacramento Valley, and 6) Coastal Area north of Los Angeles.


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1945 - Irrigation Requirements of California Crops, Bulletin No. 51