AgriMet: Modeling Evapotranspiration for Irrigation Water Management

TitleAgriMet: Modeling Evapotranspiration for Irrigation Water Management
Publication TypeConference Proceedings
Year of Conference2005
AuthorsPalmer, P. L.
Conference Name73rd Annual Western Snow Conference
Series TitleProceedings of the 73rd Annual Western Snow Conference
Date PublishedApril 2005
PublisherWestern Snow Conference
Conference LocationGreat Falls, MT
KeywordsAgriMet, irrigation, evapotranspiration, water use efficiency, crop coefficients, Kimberly-Penman, NRCS

In 1983, the U.S. Bureau of Reclamation and Bonneville Power Administration entered into a formal agreement to promote irrigation water use efficiency. This agreement resulted in the installation of a network of automated agricultural weather stations called AgriMet (for Agricultural Meteorology) in the Pacific Northwest. These stations collect and telemeter the meteorological parameters required to model crop evapotranspiration (ET). The information is used by irrigation districts, farmers, resource conservation agencies, and agricultural consultants for irrigation scheduling and related purposes. Since the initial installation of 3 stations in 1983, the network has grown to over 60 stations in Reclamation's Pacific Northwest region, 21 stations in the Great Plains Region in Montana, and seven stations in the Mid Pacific region. These automated weather stations transmit their data by the GOES satellite, and the information is used in the Kimberly-Penman 1982 evapotranspiration model to compute reference ET at each station. Crop coefficients are then applied to estimate water use for specific crops grown at each station for every day of the growing season. This information is available on the Internet, and is integrated into various on farm technical assistance programs by local agricultural consultants, the Cooperative Extension Service, and the USDA Natural Resources Conservation Service. Use of AgriMet information in irrigation scheduling results in water and energy savings, reduced soil erosion, and protection of surface and ground water supplies. Various agricultural consultants have reported water and power savings ranging from 15 to 50 percent (Dockter, 1996). Some irrigators have reported real savings of as much as $25 per acre in pumping costs when using AgriMet ET data to schedule their irrigations (Palmer, 2004).