How much water will be needed to support communities, farms and fish in the Columbia Basin and where it will come from is the focus of a near-final report from the Washington Department of Ecology's Office of Columbia River.
"The Columbia River Basin Long-Term Water Supply and Demand Forecast" is being developed by Ecology with assistance from Washington State University and Washington Department of Fish and Wildlife. A long-term supply and demand forecast is produced every five years and is due to the Legislature on Nov. 15.
A series of public workshops is scheduled for Sept. 7, 8, and 9 in Richland, Wenatchee and Spokane to share particulars of the report and to gather feedback about the preliminary findings. An online version of a workshop will be available in late September for those who cannot attend a workshop in person.
The workshops will be held:
-- Wednesday, Sept. 7, from 3 to 7 p.m., Tri-Cities West Building Room 131, WSU Tri-Cities, 2710 Crimson Way, Richland;
-- Thursday, Sept. 8, from 1 to 5 p.m., WSU Tree Fruit Research and Extension Center, Overley Laboratory Building, 1100 N. Western Ave., Wenatchee, and
-- Friday, Sept. 9, from 9 a.m. to 1 p.m., WSU Spokane County Extension Office conference rooms B and C, 222 N. Havana, Spokane.
The forecast evaluates supply and forecasts demand on three tiers: basin-wide (which includes seven states and British Columbia,) at the watershed (water resource inventory area or WRIA) level, and within a one-mile corridor along the Columbia River.
The forecast examines:
-- Water demand for four sectors: agricultural, municipal, hydroelectric, and in-stream flows.
-- Water supplies.
-- Climate change impacts.
-- In-stream flows for eight critical fish basins in eastern Washington.
"For the first time we'll have a comprehensive evaluation of what our water needs will be in the Columbia basin," said Derek Sandison, who heads Ecology's Office of the Columbia River. "This report provides a blueprint for how we invest in water supply projects. It will help tell us where and when more water is needed in eastern Washington."
Data collected for the 2011 report employs the latest modeling tools, and incorporates factors such as climate change and regional and global economic conditions into forecast calculations. The report also reflects input directly from water users in the basin.
"The report summarizes the likely changes in supply and demand over the next 20 years. Whether your interest is on changes to the Columbia River or its tributaries, inside Washington or in other states and British Columbia, Canada, this report has information that will help you make better water planning decisions," said Michael Barber, lead scientist and director of WSU's State of Washington Water Research Center.
The Columbia River basin is particularly sensitive to small changes in overall temperatures, according to the report drafters. Reduced snowfall and earlier snowmelt are predicted to influence surface water flows. The report incorporates climate change impacts on future water supplies and demands.
Water supply modeling conducted for the forecast predicts warmer, wetter winters, when water demand is low, and hotter, dryer summers, when demand peaks. More winter precipitation will fall as rain rather than snow, thus lessening available snowpack, according to a forecast fact sheet. Hotter, dryer summers will increase crop water demand and potentially shorten the growing season for some crops.
By 2030, the model predicts an increase in average annual flow in the basin of 2 percent, but the timing of flows could change dramatically depending on location within the basin. For example, flows on the Columbia River at Bonneville Dam are expected to increase by up to 35 percent from November to May, but decrease by up to 9 percent from June to October.
WSU also evaluated the effect of making more water supply available through new projects funded by OCR, and the effect of recovering the cost of water supply development from new permittees. The report considered projects ranging from 100,000 acre-feet to 800,000 acre-feet at cost of $25 to $200 per acre-foot per year, the fact sheet says.
“The model predicted little impact on acreage irrigated and crop selection at $25 per acre-foot, with significant changes as water supply development costs approached $200 per acre-foot per year or availability increased to 800,000 acre-feet, the fact sheet says.
The report also evaluates stream conditions for critical rivers throughout eastern Washington through a "Columbia River In-stream Atlas" developed by WDFW.
"The In-stream Atlas evaluates fish stocks and flow and habitat conditions in eight fish critical “WRIAs.”
“It will help the Office of Columbia River and other funding agencies target water supply improvement projects in locations where fish need it most," said Teresa Scott, Water Resource policy coordinator for WDFW.
Ecology and other state natural resources agencies divided the state into 62 WRIAs to delineate the state's major watersheds
The “in-stream atlas” focuses on the Walla Walla, Middle Snake, Yakima (three WRIAs), Wenatchee, Methow and Okanogan river basins. The atlas incorporates maps and information on streamflow restoration priorities and stream-level information on fish life history stages.
The atlas shows that recovery opportunities exist in all eight WRIAs to improve fisheries, and that adopted in-stream flows for many of these WRIAs are routinely not met, according to the fact sheet. The WDOE’s OCR will use these tools to ensure that new water supply projects it funds will benefit in-stream flow and protect fish habitats
Agriculture is the largest single user of water in eastern Washington. The combined influences of climate change, economic trends and population growth will result in an increase in the amount of water needed for agricultural irrigation.
The report also predicts that by 2030, diversions for cities and communities in eastern Washington will increase by approximately 24 percent or an additional 109,000 acre-feet per year, based on expected population growths.
Hydropower use in eastern Washington is expected to remain fairly stable over the next 20 years, with increases in demand being met through conservation projects and power from other sources.
More information on the forecast is available at http://www.ecy.wa.gov/programs/wr/cwp/wsu_supply-demand.html