How to meet the water needs for Eastern Washington's communities, industry, crops and fisheries is the focus of a report recently finalized by the Washington Department of Ecology's Office of Columbia River.
The forecast evaluates likely changes in surface water supply and demand in Eastern Washington over the next 20 years.
Authored by the Department of Ecology with WSU and the Washington Department of Fish and Wildlife, the forecast is the most comprehensive look at surface water supply and demand to be produced in the state.
According to the forecast, water managers will need to pay particular attention to changes in temperature and precipitation. Hotter, drier summers and warmer, wetter winters in Eastern Washington will create new water supply challenges, it notes.
Reduced snowpack, more rain in winter and earlier snowmelt are predicted to lessen the amount of water available in late summer and early fall when demands are high.
"It will take innovative water solutions to meet existing and future water demands in the basin," said Derek Sandison, Ecology's Office of Columbia River director. "As we identify these needs, we can target where we make capital investments in infrastructure projects to meet those needs, both instream and out-of-stream."
Employing the latest computer modeling tools, the report incorporates factors such as climate change, population growth and regional and global economic conditions into forecast calculations.
It also leverages and further builds on modeling tools and datasets developed by the University of Washington Climate Impacts Group.
In 2006, the state legislature tasked ecology offiicals with developing new water supplies for the Columbia River Basin for both instream and out-of-stream benefits.
The water forecast was requested by the state legislature, as part of a program to focus meeting future needs of fish, irrigators and groundwater supplies.
Meeting current demands is already a challenge. During drought years, some 360 junior water rights may be curtailed or interrupted along the Columbia River, resulting in an unmet need of as much as a 310,000 acre-feet in severest drought years.
Some 164,000 acre-feet of surface water is needed to irrigate 70,000 acres now relying on declining aquifers in the Odessa Subarea, and 450,000 acre-feet of new supply must be found to meet needs in the Yakima Basin.
According to the recently published forecast, in the next two decades the water demand for cities and communities in Eastern Washington will increase by approximately 24 percent. The demand for irrigation water is expected to rise by nearly 2 percent.
At the same time, hydropower use in Eastern Washington is expected to remain stable over the same time, with increases in energy demand being met through conservation projects and power from other energy sources.