Authors:

Richard L. Snyder
Biometeorologist, Cooperative Extension, Davis
Brenda J. Lanini
former Staff Research Associate, Cooperative Extension, Davis
David A. Shaw
Postgraduate Researcher, Cooperative Extension, Davis
William O. Pruitt
Irrigation Engineer, Department of Land, Air and Water Resources, Davis

UC Cooperative Extension
Division of Agriculture and Natural Resources
Leaflet 21428
If you have comments or suggestions, please email lawrweb@ucdavis.edu

Last reviewed December 19, 2002

    Using Reference Evapotranspiration (ETo) and Crop Coefficients to Estimate Crop Evapotranspiration (ETc) for Trees and Vines


     Introduction

    Reference evapotranspiration (ETo) information is now available in many agricultural areas of California through the California Irrigation Management Information System (CIMIS). Direct access to real-time (daily) weather and ETo information through a computer dialup service can be obtained by writing:

    California Department of Water Resources
    Office of Water Conservation
    PO Box 942836
    Sacramento, CA 94236-0001

    These daily real-time ETo estimates are used by growers to determine a refined irrigation schedule that can optimize profits relative to the use of water

    Historical average or "normal" ETo values are useful in determining an average or normal irrigation schedule for your crop that will give good results in most years. Daily normal ETo for many locations within California can be determined using the method and average monthly ETo accumulations given in "Determining Daily Reference Evapotranspiration", UC Leaflet 21426.