In Spring 2021, the Washington State Department of Ecology (Ecology) started the public review process for the TransAlta water bank—at 28,000 acre-feet per year, the biggest water bank in the state to date. This is the first significant water bank for Southwestern Washington and came together through years of planning, working with Chehalis basin stakeholders, and extending the water rights life of a Chehalis River hydropower project. The trigger for this new water bank is TransAlta retiring its decades-old hydropower plant on the Skookumchuck River, thus freeing up tens of thousands acre-feet of water rights for the basin.
Water banks Add Life to Thirsty Watersheds
In water-scarce basins — even on the western/‘rainy’ side of Washington State -- water banks provide an innovative mechanism to reuse water rights; once water is no longer needed for its original purpose it can be made available to meet new needs. Water banking involves a partnership between the holders of valid water right holders and Ecology. While the water right holder controls how new uses are permitted, the State of Washington is responsible for determining the amount of water that will be preserved, and then protecting that water from other users.
The TransAlta water banking process has proceeded through an Aspect-led permitting path that involves an exhaustive vetting of the historical water use, and the development of a new process to guide the reallocation of future uses. Water rights that were issued for other purposes – such as industrial supply – are converted to instream flows purposes, and generally become available to mitigate new uses.
The TransAlta water bank solution is a textbook example of how pre-planning saved a significant block of valid water rights from relinquishment for non-use. Water that had been allocated for a highly consumptive out-of-stream use will now be held in trust for instream flows, with select new uses being reallocated for new purposes under Ecology’s permitting process. The end result will be a combination of water that will remain instream, and new water right permits for new uses.
Tapping the Skookumchuck River to Boost Chehalis Basin’s Water Future
Stretches of the Skookumchuck River, like this one taken near the City of Centralia, will soon receive more water.
The TransAlta water bank is situated near Centralia, Washington, along the Skookumchuck River—a major tributary of the Chehalis River. For decades, TransAlta has used the waters of the Skookumchuck to produce coal-based electrical power; however, as the company began to make plans for a life after coal, it also had the foresight to make plans for its water rights, which represents more than 50 cubic-feet per second (that is 22,500 gallons per minute) and 28,000 acre-feet per year of out-of-stream uses.
TransAlta’s retired Unit 1 of its Centralia, Washington coal-fired power plant in 2020. Unit 2 is planned to close by the end of 2025
According to TransAlta’s Water Bank Overview FAQ, this is “enough water to fill 14,000 Olympic-sized swimming pools or irrigate 14,000 acres of farmland.”
Seeding 28,000 Acre-Feet of Water for Fish and Agriculture in the Chehalis Basin
While the budding water bank is still in the early planning stages, several new water uses have already been identified. One deal involves making water available to the City of Centralia for its future needs and to provide a source of mitigation water to offset the impacts of future private wells throughout the watershed. TransAlta also envisions making water available for the basin’s expanding agricultural needs and ensuring leftover water remains instream to protect aquatic resources.