2021 COLUMBIA RIVER BASIN LONG-TERM WATER SUPPLY AND DEMAND FORECAST RELEASED

2021 COLUMBIA RIVER BASIN LONG-TERM WATER SUPPLY AND DEMAND FORECAST RELEASED

The latest Columbia River Basin Long-term Water Supply and Demand Forecast (Forecast), released by the Washington Department of Ecology in partnership with Washington State University and the State of Washington Water Research Center, outlines how changing climate, trends in agricultural crops and population growth may affect water availability across Eastern Washington over the next 20 years. The report analyzes at the watershed level how hard it may be for the region to meet both instream and out-of-stream water demands at certain times of year.

The forecast builds on past reports by taking a comprehensive look at water supplies and both out-of-stream and in-stream demands. Compared to previous reports, the report improved the ability to understand groundwater supplies, as well as municipal and agricultural demands and likely impacts on flows for fish. The report also adds a longer term, 50 year outlook through 2070, to more deeply explore anticipated climate impacts.

Key Findings

Key findings in the Forecast highlight the four main types of changes that are leading to vulnerabilities across eastern Washington:

• The timing of surface water supplies is shifting earlier in the season, especially in the snowmelt-dominated Cascades watersheds.
• Future changes in population and in agriculture in eastern Washington could lead to increases in instream and out-of-stream demands for water.
• Groundwater levels are declining in most aquifer layers and groundwater subareas across eastern Washington.
• Local increases in out-of-stream demands are expected, converging with local decreases in water supply, such as in the Yakima River Basin.

A technical supplement for 2021 Columbia River Basin Long-term Water Supply and Demand Forecast will be available in mid-August