Dungeness Off-Channel Reservoir Water Storage Proposal Summary
Brief Proposal Description: Low flow in the Dungeness River is a significant limiting factor for four ESA listed species of salmon and steelhead. Low flows are primarily a seasonal challenge, occurring in the late summer and early fall. Around mid to late August, human needs for irrigation water peak, Chinook and Pink salmon return to spawn, the snowpack feeding the river is mostly depleted, and the river drops to its lowest flow.
In all but the wettest years these low flows are insufficient to meet the needs of salmon. The biggest and most senior established water rights in the basin belong to the Dungeness irrigators. For more than a century the Dungeness Valley has been irrigated with water directly from the Dungeness River. In the last 20 years Dungeness irrigators and basin partners have invested considerable resources into to conserving and enhancing flow in the River. However, in dry years there is still not enough flow in the river to support salmon and meet out of stream water needs.
The solution is to store water during the winter and spring when flows are plentiful, saving this water for later in the year when river flow is in short supply. In addition to significantly increasing low flows this is a multi- benefit project that will capture stormwater and prevent downstream flooding in the City of Sequim, provide opportunities for aquifer recharge, create a new County park with river access and recreational opportunities and ensure the sustainability of agriculture in the Dungeness Valley.
Partners: Clallam County, Jamestown S’Klallam Tribe, City of Sequim, Dungeness Valley Irrigators, Clallam Conservation District & Washington Water Trust
Reservoir Size: 88 Acre reservoir site within a new 320 Acre County Park
Storage Capacity: 1500 acre feet which would provide about 25 cubic feet per second during the critical low flow period of Aug 15th-Sept 15th (the last month of the irrigation season)
- Stream Flow Restoration For Salmon The project would restore up to 25 cfs of flow to the Dungeness River, allow the target flow restoration goal of 105 cfs to be met and drastically reduce the need to divert water out of the river in the last month of the irrigation season benefiting ESA listed Salmon and Steelhead.
- Stormwater Management The project has the potential to assist the City of Sequim with their stormwater needs by intercepting storm flows before they reach City infrastructure depending on the design specifications.
- Aquifer Recharge The project will provide storage of water that can be used for aquifer recharge either on or off-site to restore stream flows or generate mitigation credits for the Dungeness Water Exchange.
- Long-Term Agricultural Viability Secure access to water for irrigation is critical to maintaining agriculture in the Dungeness Valley, this project will ensure that fish can thrive and agriculture can continue irrigating without negatively impacting flows.
- Recreation The project site is currently owned by Department of Natural Resources and will be eventually owned and managed by Clallam County as a new public park with hiking, biking, wildlife viewing and river access opportunities.
Project Status: Preliminary Design Complete, Cost Benefit Analysis In Process; Grants applied for: Floodplains by Design, Salmon Recovery Funding Board, Puget Sound Restoration Acquisition Fund, FEMA Hazard Mitigation Grant. DNR support for transferring the property, Clallam County has applied for a Trust Land Transfer of the Parcel.