Yakima Watershed and River Systems Management Program Completed

The Yakima River Basin covers 6,200 square miles, beginning in the eastern slopes of the Cascade Range, where precipitation is more than 90 inches annually, and ending in the arid agricultural lands where the river discharges to the Columbia River. The basin is representative of water-use and water-resource management in the West, and because management of its waters is one of the most difficult tasks the USBR undertakes in the western United States, the WARSMP program approach was used to study this basin. For its part in the study, the USGS is developing methods to estimate mean annual streamflow for ungaged subbasins and the stream channel network to provide a data set of natural and unregulated streamflow for use in the watershed models, and then constructing, calibrating, and testing four watershed models for the basin. The results of this study can be used by water managers to assess the availability and use of water in the basin on a near-real-time basis.

Yakima Watershed and River System Management Program

Introduction - The Watershed and River System Management Program (WARSMP) is a cooperative program between Department of the Interior agencies. The WARSMP is sponsored by the Water Resources Division of the U. S. Geological Survey (USGS) and the Science and Technology Research Program of the U.S. Bureau of Reclamation (USBR). The purpose of WARSMP is to develop, test, and implement a framework for the management of water resources in the Reclamation Act States. The framework will be a fully-integrated data-centered system of physical process models--MMS (Modular Modeling System), resource-management models--PRSYM (Power and Reservoir Systems Model), forecast models, and graphical user interfaces (GUI). The MMS and PRSYM are linked through a data management system--HDB (Hydrologic Database), as are GIS, queries and displays, and real-time data and processing. As of Fiscal Year (FY) 1996 the system has been applied to the San Juan River Basin--a tributary basin to the Colorado River that has a drainage area of about 23,000 square miles.

The collaborative work of the program will be focused on the Yakima River Basin beginning in FY 1997. The Yakima River Basin is representative of water-use and water-resource management in the West, and management of its waters is one of the most difficult tasks the USBR undertakes in the western United States. Program elements will be accomplished by the USGS and USBR. The USGS tasks will be completed by staff of the USGS Washington Water Science Center Office (Tacoma) and by the National Research Program (NRP) staff in the Central Region (Denver). The USBR tasks will be completed by the Yakima Field Office (Yakima), the Upper Columbia Area (Yakima), the Pacific Northwest Regional office (Boise), and the Science and Technology Research Program (Denver).

Study area and background - The Yakima River Basin is situated in eastern Washington, has a drainage area of about 6,200 square miles, and produces an average annual runoff of 3,200 cubic feet per second. The river basin heads on the east slope of the Cascade Range where annual precipitation is more than 90 inches and terminates where the river discharges to the Columbia River in the lower, arid part of the basin, which receives about 6 inches of precipitation annually. Altitudes in the basin range from about 8,000 feet in the headwaters to about 400 feet near the mouth of the Yakima River; the highest altitude in the basin is Mt Adams at 12,307 feet. In the upper parts of the basin, the river has a medium to high slope and it passes through forested lands and deeply incised canyons. Whereas, in the lower parts of the basin, where most of the water use occurs, the river follows a meandering course through hilly and flat agricultural lands to its mouth after traveling nearly 300 miles. Major tributaries to the Yakima River include the Cle Elum, Kachess, Teanaway, Bumping, American, Tieton, and Naches Rivers; there are also numerous small streams tributary to the river.

Agricultural is the predominant economic activity in the basin, followed by recreational and timber use. About 2,400,00 acre-feet (1,300 cubic feet per second) is diverted for irrigation of about 500,00 acres; nearly 45 percent of the diverted water is eventually returned, at varying time-lags, to the river system. There are five major storage reservoirs in the basin that are capable of storing 1,065,400 acre-feet or about 28 percent of the natural flow of the river. The basin has more than 80 canals, 5 diversion dams, 15 major return flows, and numerous smaller return flows. The major canals divert up to an annual rate of about 400 cubic feet per second, but the majority of the canals divert at an annual rate of 5 to 10 cubic feet per second.

Relevance and Benefits - The Yakima River Basin watershed modeling project is part of joint U.S. Bureau of Reclamation/U.S. Geological Survey program, termed WARSMP--Watershed and River System Modeling Program. The project has direct benefits to the Nation by developing and applying tools to improve the operations of USBR systems in the western United States in general and in the Yakima Basin in particular. It meets the overall mission goals of the USGS and expands on the strategic plans to improve tools and to develop methods to analyze problems at the watershed scale. This project builds on existing relations with a sister Department of the Interior agency and is developing long-term relations with many stakeholders.