The goal of this publication is to provide water users, consultants, water agency personnel, and others throughout California with information that will: (a) help individual water users with irrigation scheduling and system design and (b) help agricultural water agency personnel with water balances and future planning.

The tables in this publication represent the consolidation of results from thousands of annual ET simulations that accounted for crop, rainfall (wet, dry, or “typical”), soil, and irrigation method in each of 13 major ETo zones in California. The annual simulations used daily water balances at the soil surface, crop canopy, and soil root zone.

When using these tables, one must keep the following in mind:

  1. The tables account for soil evaporation 365 days out of the year. Many other published ET tables ignore ET that occurs when a crop is not present.
  2. The crop/soil ET values assume typical surface (furrow, border strip, and basin) irrigation management (except for grapes in Zones 3, 6, and 8, where drip irrigation is assumed). Procedures for adjusting the ET values for special conditions, various irrigation methods, etc. are explained in this publication and in the original ITRC Report 02-001 (found at www.itrc.org).
  3. The ET values are given for irrigation scheduling and system design purposes. For persons interested in computing water balances, the ET values must be de-rated because in most fields there are some bare spots and areas with decreased vigor – meaning that the field average ET is less than the crop/soil ET in areas of the field with healthy crops.


Bioresource and Agricultural Engineering

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URL: https://digitalcommons.calpoly.edu/bae_fac/184