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 http://www.ecy.wa.gov/programs/wr/cwp/forecast/forecast.html evaluates likely changes in surface water supply and demand in eastern Washington over the next 20 years.
The Columbia River Basin Long-Term Water Supply and Demand Forecast will serve as a guide for developing new water supplies in eastern Washington. Authored by Ecology with Washington State University 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.
“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. “The forecast helps to identify where additional water supply is currently needed and where it will be needed in the future. As we identify these needs, we can target where we make capital investments in infrastructure projects to meet those needs, both in-stream 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.
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. 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.
Stream conditions for the tributaries in eight river basins that are critical for fish spawning, rearing and survival are identified and evaluated in a “Columbia River Instream Atlas,” a companion tool developed by WDFW.
“The Instream Atlas will serve as a great tool to help identify where fish needs are and opportunities to match water development projects with those needs,” said Teresa Scott, WDFW’s natural resource policy coordinator. “Supporting fisheries is an important component of the state’s mission to develop water for the benefit of all our water needs.”
In 2006, the Legislature tasked Ecology with developing new water supplies for the Columbia River Basin for both in-stream and out-of-stream benefits. The program is directed to focus on projects that create opportunities to issue new water rights, acquire commensurate water in support of streamflows for fish, deliver water to Odessa Subarea irrigators relying on groundwater supplies that are diminishing and find water to offset the needs of junior water users whose rights may be interrupted during drought. In addition, legislators directed Ecology to prepare a supply and demand forecast.
Meeting current demands is already a challenge. During drought years, Columbia River in-stream flows fall as much as 13.4 million acre-feet below Washington Administrative Code requirements for fish.
In the tributaries, in-stream flows are 500,000 acre-feet below what is required.
Additionally, during drought 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 River basin.
At 6.3 million acre-feet per year, agriculture is the largest single diverter and consumer of water in Eastern Washington among the many water users along the Columbia River and its tributaries. Other users include domestic, municipal and industrial water consumers, as well as power generators and fisheries that rely on water that stays in the rivers.
By 2030, the combined influences of climate change, economic trends and population growth will result in a 1.9 percent (approximately 170,000-acre-feet per year) increase in the amount of water needed for agricultural irrigation.
In the next two decades, the forecast predicts the water demand for cities and communities in eastern Washington will increase by approximately 24 percent or an additional 117,500 acre-feet per year, based on expected population growth and associated industrial development.
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.
Since 2006, OCR has developed approximately 150,000 acre-feet of new water supply by tapping into water stored behind Grand Coulee Dam, funding irrigation piping and infrastructure improvements, and water right acquisitions. Another 200,000 acre-feet is in near-term development, with several projects coming on line. Permits will soon be issued from water stored at Sullivan Lake, and streamflows bolstered and new acreage watered through a pump and conservation project at Red Mountain.
The supply and demand forecast is updated every five years. The next report is due in 2016. The forecast is available online at: http://www.ecy.wa.gov/programs/wr/cwp/forecast/forecast.html