A study for the U.S. Bureau of Reclamation and Washington Department of Ecology identifies 11 possible sites for new storage dams in Washington that would create huge off-stream reservoirs in the Columbia River Basin. The report says all 11 sites have the potential for hydropower generation.
MWH, an engineering consulting firm, conducted the study to evaluate potential storage sites that could retain a minimum of 300,000 acre-feet for annual use. It also prepared a 180-page report, “Off-Channel Storage Assessment Pre-Appraisal.” The December 2005 report is the result of a 2004 agreement by BuRec, Washington, and a number of irrigation districts to assess the potential to store additional water from the Columbia River mainstem. Eventually, costs and benefits of alternative sites are to be assessed.
Water would be stored by diverting it from existing reservoirs on the Columbia River mainstem. Grand Coulee is the most upstream dam on the Columbia in Washington, and the only mainstem dam with substantial storage. The most downstream mainstem dam is Bonneville.
The evaluation: identified potential 300,000 acre-foot storage sites within ten miles of the mainstem of the Columbia River; assessed the availability of water to be stored; and developed a preliminary inventory of site-related physical, environmental, and cultural characteristics. The study developed initial estimates of capital costs of each alternative for each site, and provided evaluation criteria for assessing the alternative sites. It stopped short of developing reliable estimates of project costs and benefits but did include a table of cost estimates for the 11 potential off-channel storage sites totaling more than $17 billion.
All sites have potential for hydro generation
The report said all proposed off-stream storage sites have the potential for hydropower generation upon release of stored water.
“Evaluation of power generation from identified potential off-stream storage sites is dependent on the water storage and release schedule and other factors, and is beyond the scope of the analysis for the pre-appraisal study,” it said. “Potential power generation and associated cost estimates for power generation and transmission infrastructure should be evaluated in appraisal-level studies and subsequent feasibility studies on potential off-stream surface storage.”
The report says each new diversion would decrease flows in the Columbia River downstream of the diversion point. That reduced flow would cause a reduction in hydroelectric production at mainstem dams and affect economics. In addition to the reduced mainstem hydro generation, under several scenarios there would be an increase in power consumption associated with pumping the diverted water.
The 11 sites, chosen from an initial list of 20 possible sites, and including total storage volume, in acre-feet: Alder Creek, 331,000; Crab Creek, 2,653,000; Foster Creek, 1,321,000; Goose Lake, 3,619,000; Hawk Creek, 1,550,000; Kalama River, 1,185,000; Mission Creek, 481,000; Moses Coulee, 4,126,000; Ninemile Flat, 1,024,000; Rock Creek East, 998,0000; and Sand Hollow, 1,228,000.
State approves Columbia River Water Resource Management law
Meanwhile, the state of Washington approved a law for managing Columbia River Basin water. It commits the state to developing new water storage and conservation projects in the Columbia Basin, such as those in the BuRec and Washington Department of Ecology report.
“For 30 years, people have been wrangling over the best way to support the water needs of eastern Washington, and protect and restore our native salmon runs on the Columbia River,” Gov. Chris Gregoire said upon signing the bill Feb. 16. “Now we have a road map towards achieving those goals.”
The law provides a formula for allocating newly stored water, and creates mechanisms to initiate conservation and improve river management. Two-thirds of newly stored water will be available for new out-of-stream uses, such as farming, industry, and municipal growth, while one-third is to be allocated to stream flows for fish.