Modeling crop water use in the Pacific Northwest: The USBR AgriMet program

Water supplies are limited in the arid western United States, and demands on water resources continue to grow. Environmental concerns for fish and wildlife, endangered species, and recreation call for reductions in consumptive use, leaving more water in rivers, lakes and streams. In many states in the west, irrigated agriculture accounts for an overwhelming majority of total consumptive water use. Recognizing the opportunity for water conservation in irrigated agriculture, the U.S. Bureau of Reclamation, in partnership with Bonneville Power Administration, began installing a network of agricultural weather stations in the Pacific Northwest in 1983. From an initial 3 stations, the network has grown to over 50 stations in Idaho, Oregon, Washington, and Montana. The network, called AgriMet (for Agricultural Meteorology), measures the weather parametersrequired to model crop evapotranspiration, or 'ET'. These data are telemetered by satellite to a receiving station in Boise, Idaho, where they are incorporated into the Kimberly-Penman ET equation. Each day during the growing season, crop water use charts are developed and disseminated via the World Wide Web and a dial-up computer system to irrigators and agricultural consultants in the Northwest By knowing the water holding capacity of the soil and the root depth of the crops, irrigators can use ET information to apply the right amount of water to their crops at the right time. Benefits of scientific irrigation scheduling include water conservation, reduced energy and fertilizer cost, reduced soil erosion, and protection of water quality by reducing runoff and groundwater infiltration of pesticide and fertilizer laden water.