Dungeness Off-Channel Reservoir decision support

SEI is working with the Washington Water Trust and Clallam County, Washington to build a water allocation model of the Dungeness River in the Water Evaluation and Planning (WEAP) modeling platform to evaluate the potential off-channel reservoir project design.

The Dungeness River is a 28-mile-long river located on the eastern side of the Olympic Peninsula in the ancestral home of the Klallam (S’Klallam) Tribe. Located in the rain shadow of the Olympic Mountains, the Dungeness River basin is part of a region that receives less rainfall and more sunshine than any place in the Puget Sound region.

Low flow in the Dungeness River is a significant limiting factor affecting the survival of four species of endangered or threatened salmon and steelhead. During years of lower snowpack, there is not enough flow in the river to support salmon and meet out-of-stream water rights for irrigation. To address these limitations, an off-stream reservoir has been proposed to provide multiple benefits including, but not limited to, irrigation supply and aquatic habitat.

The WEAP model will quantify streamflow and water delivery to agriculture under varying conditions of reservoir operations and future climate to help stakeholders in the Dungeness Reservoir Work Group understand the impacts on water supply and instream flow benefits of the reservoir designs. The results will ultimately inform the reservoir design to maximize community benefits.