Updated evapotranspiration (ET) and net irrigation requirement (NIR) estimates are available through this site for areas in Idaho. New ET calculation procedures were employed including an updated reference equation ( the ASCE standardized Penman-Monteith method) and an updated procedure to calculate crop coefficients that considers the impact of surface wetting by irrigation and precipitation on total evaporation. ET was calculated for daily, monthly, and annual timesteps for 123 weather station locations across Idaho. In addition to ET and NIR estimates for agricultural crops grown in Idaho, ET estimates are available for a number of native plant systems (wetlands, rangelands, and riparian areas) and open water surfaces. The ET and NIR estimates are intended for use in design and management of irrigation systems, for water rights management and consumputive water right transfers, and for hydrologic studies. ET estimates are available for all times during the calendar year to provide information for land application design, operation, and management of waste streams from agriculture, food processing and other sources.

These dynamic web pages allow you to access historical ET data for the State of Idaho at various locations. Currently, the data is based on 112 NWS cooperative weather stations and 16 AgriMet stations through out the state.

Find and explore the summary data for stations and land covers: Click on this link to locate stations by county or Please select a station from the following list: NWS -- Aberdeen Experiment Station AgriMet -- Aberdeen AgriMet -- Afton WY NWS -- American Falls 1SW NWS -- Anderson Dam NWS -- Arbon 2 NW NWS -- Arco NWS -- Arrowrock Dam NWS -- Ashton AgriMet -- Ashton NWS -- Bayview Model Basin NWS -- Blackfoot NWS -- Bliss NWS -- Boise 7N NWS -- Boise WSFO Airport NWS -- Bonners Ferry NWS -- Brownlee Dam NWS -- Bruneau NWS -- Buhl NWS -- Burley FAA AP NWS -- Cabinet Gorge NWS -- Caldwell NWS -- Cambridge NWS -- Cascade 1 NW NWS -- Castleford 2 N NWS -- Challis NWS -- Coeur d Alene 1 E NWS -- Cottonwood NWS -- Council NWS -- Deer Flat Dam NWS -- Driggs NWS -- Dubois Experiment Stn NWS -- Dworshak Fish Hatchery NWS -- Elk City NWS -- Elk River 1 S NWS -- Emmett 2 E NWS -- Fairfield AgriMet -- Fairfield NWS -- Fort Hall Indian Agency AgriMet -- Fort Hall NWS -- Galena NWS -- Garden Valley RS NWS -- Glenns Ferry AgriMet -- Glenns Ferry NWS -- Grace NWS -- Grand View AgriMet -- Grand View NWS -- Grangeville NWS -- Grasmere NWS -- Hagerman 2 SW NWS -- Haily Ranger Stn NWS -- Hamer 4 NW NWS -- Hazelton NWS -- Hill City NWS -- Hollister NWS -- Idaho City NWS -- Idaho Falls 16 SE NWS -- Idaho Falls FAA ARPT NWS -- Idaho Falls 46 W NWS -- Island Park NWS -- Jerome NWS -- Kellogg AgriMet -- Kettle Butte NWS -- Kilgore NWS -- Kooskia NWS -- Kuna NWS -- Leadore NWS -- Lewiston WB AP NWS -- Lifton Pumping Stn NWS -- Lowman NWS -- Mackay Ranger Stn NWS -- Magic Dam NWS -- Malad NWS -- Malad City NWS -- Malta 1 NE AgriMet -- Malta NWS -- May NWS -- McCall NWS -- McCammon NWS -- Minidoka Dam AgriMet -- Monteview NWS -- Montpelier NWS -- Moscow Univ of Idaho NWS -- Mountain Home 1 W AgriMet -- Nampa NWS -- New Meadowns Ranger Stn NWS -- Nezperce NWS -- Oakley NWS -- Ola NWS -- Orofino NWS -- Parma Exp. Station AgriMet -- Parma NWS -- Payette NWS -- Picabo AgriMet -- Picabo NWS -- Plummer 3 WSW NWS -- Pocatello WB AP NWS -- Porthill NWS -- Potlatch 3 NNE NWS -- Preston 3 NE NWS -- Rexburg Ricks College AgriMet -- Rexburg NWS -- Reynolds NWS -- Richfield NWS -- Riggins Ranger Stn NWS -- Rupert AgriMet -- Rupert NWS -- St Anthony NWS -- Saint Maries NWS -- Salmon NWS -- Sandpoint KSPT NWS -- Shoshone NWS -- Soda Springs NWS -- Stanley NWS -- Strevell CAA Airport NWS -- Swan Valley 1 W NWS -- Tetonia Experiment Stn NWS -- Three Creek NWS -- Twin Falls 2 NNE NWS -- Twin Falls 3 SE NWS -- Twin Falls WSO AgriMet -- Twin Falls NWS -- Weiser
Explore annual and monthly trends in reference evapotranspiration and precipitation for all the ETIdaho stations by following the hot links below. Be patient, we are computing trend information each time the page is loaded.
Annual Trends	Monthly Trends

A pdf copy of the report submitted to IDWR, Evapotranspiration and Consumptive Irrigation Water Requirements for Idaho, Research Technical Completion Report is available for download here.

These estimates for evapotranspiration and precipitation deficit superceed those published by Allen and Brockway (1983). For historical reference, the 1983 estimates can be found at http://www.kimberly.uidaho.edu/water/appndxet/

This work and report were prepared by the University of Idaho Research and Extension Center at Kimberly, Idaho under contract with the Idaho Department of Water Resources. Work was supported by funding from IDWR and the Idaho Agricultural Experiment Station and Idaho Engineering Experiment Station. The authors gratefully acknowledge the long-term evapotranspiration data collection and long-standing advice provided by Dr. James L. Wright, USDA-ARS Kimberly (ret.), the more than two decades of high quality agricultural weather data collection by the U.S. Bureau of Reclamation AgriMet system, and the very long-standing, routine data collection by the hundreds of cooperative weather station volunteers across the state who, for more than one-hundred years, have faithfully observed daily air temperature and precipitation.

The citation for the evapotranspiration data used from this site should be: Allen, Richard G. and Clarence W. Robison, 2006 (Revised 2007). Evapotranspiration and Consumptive Irrigation Water Requirements for Idaho, Research Technical Completion Report, Kimberly Research and Extension Center, University of Idaho, Moscow, ID.

Questions regarding the data should be addressed to Clarence W. Robison or Richard G. Allen, University of Idaho, Kimberly Research and Extension Center, 3793 North 3600 East, Kimberly, ID 83341. Telephone (208)-423-6610