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Projects > Water Balance > CA Crop and Soil ET

California Crop and Soil Evapotranspiration

 Date: 2003
 Location: California
 Sponsors: CALFED, DWR, and USBR
 Reports Available:   ITRC Report No. 03-001
 Online Data:  Online Evapotranspiration Data


ETo Zone Map

ETo Zone Map of California

The purpose of this study was to create a publication presenting evapotranspiration for crops and soils in 13 California Dept. of Water Resources (DWR) Reference Evaporation Zones (ETo Zones) for three types of precipitation years:

  • typical
  • wet
  • dry


For persons interested in irrigation scheduling and design, the publication includes instructions on how to adjust ET values for:

  1. different irrigation systems
  2. different growing seasons


It also includes instructions, for persons doing regional or irrigation district water balances, on how to adjust values for:

  1. bare spots and decreased plant vigor
  2. multiple crops on the same field


One of the main purposes of this project was to provide California water users with crop/soil ET values that take into account regional environmental and management differences.  Furthermore, with the ETo and crop/soil ET information presented in each table, crop coefficients can be calculated with relative ease for regions throughout the state.

The resultant publication, ITRC Report No. 03-001, contains the most comprehensive crop/soil ET values available to date for California.  The data can also be accessed on the ITRC website's Online Evapotranspiration Data section.