Restoration of Alluvial Water Storage in Chelan County, WA


With changing climate conditions and intensified human use, the natural infrastructure provided by healthy, functioning watersheds—wetlands, watercourses, aquifers, and floodplains—has significantly been diminished. One of the greatest opportunities for streamflow restoration lies in restoring the watershed’s ability to naturally store and release water by reconnecting incised channels to their alluvial floodplains. Both observational and modeling studies have demonstrated that re-aggradation of incised reaches can result in a 10-20% increase in baseflow early in the dry season and that increasing water storage through stream restoration is a sustainable strategy to address water scarcity into the future. When compared to traditional water storage approaches such as constructed reservoirs, stream restoration can offer a multi-benefit approach to increase natural water storage while providing benefits to riparian and wetland function, fish and wildlife habitat, water quality, fire resilience, and climate change adaptation. Since 2018, Natural Systems Design and Coastal Geologic Services has been collaborating with Chelan County Natural Resources Department (CCNRD) to quantify streamflow restoration opportunities throughout the Wenatchee watershed in Chelan County. CCNRD and NSD + CGS developed a GIS-based screening framework to compute the restorable sub-surface water storage and associated streamflow contribution per restored river mile derived from reach-scale valley widths, extents of incision, and stream gradients. Model results were utilized to identify and prioritize areas of high channel incision with potential for alluvial floodplain restoration and two pilot implementation projects were identified, designed, and implemented. Pre- and post-project monitoring have demonstrated geomorphic effect, localized increase in groundwater levels, and changes in the health and vigor of wetland and riparian specific vegetation in response to the projects.
The scientific basis for this approach along with an overview of various components of this effort are
described in the following presentations and report:

 NSD + CGS – CCNRD – Alluvial Water Storage Restoration in the Wenatchee Basin – June 2022 – LOW RES.pdf

Abbe and Dickerson-Lange 2019 -Channel incision and the loss of water storage – RCO Salmon Recovery Conference.pdf

Dickerson-Lange 2019 – Identifying and quantifying restorable water storage in the Wenatchee Basin – RCO Salmon Recovery Confere.pdf

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