Deschutes Estuary
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Situated below the Washington State Capitol campus in Olympia, WA, the Deschutes Estuary became Capitol Lake upon construction of the Fifth Avenue Dam in 1951. Prior to the structure, the estuary was a tidally-dominated system at the southern end of Budd Inlet, Puget Sound, that experienced a tidal range of approximately 5 m (15 ft) and received freshwater input from the Deschutes River. Since dam construction, an estimated 60 to 80% of suspended sediment transported by the river has been trapped by the lake (George and others, 2006). Since the mid-1970s, several dozen studies investigating sediment removal, water quality and maintenance protocols have been conducted to preserve Capitol Lake. Portions of the lake were dredged twice (1978 and 1986) even as the shoreline was altered by the construction of various parks and highway improvements. In spite of these efforts, by 2004, lake volume had decreased by 28%. Sediment management, water quality and invasive species present challenges for on-going management of Capitol Lake. - PWA 2008
Nearshore Strategies Data Report
Cereghino et al 2012 completed a soundwide analysis to identify and describe river delta sites in Puget Sounds as part of a nearshore ecosystem restoration strategy (using remote sensing data c. 2000-2006). The following narrative of this delta site was developed to support distribution and use of analysis results:
- The Deschutes Delta in the South Sound Sub-basin historically contained 13 acres of vegetated wetland along a 9 km shoreline. The delta receives freshwater and sediment from a 46,211 square kilometer watershed. These characteristics make this system the 13th largest delta out of 16 systems in Puget Sound.
- Simenstad et al 2011 found that this system had lost none of its vegetated tidal wetlands, but 100% of its shoreline length. Of the remaining shoreline, 97% shows some evidence of infrastructure development. In the surrounding uplands, 85% of land is estimated to have greater than 10% impervious surface. Across the watershed, 74% of land is estimated to have greater than 10% impervious surface. Based on these paramters, the site was given a degradation score of 58 out of 100, making it the 3th most degraded delta in Puget Sound. It faces a high risk of future development locally, and a high risk of development across the watershed. All of the watershed is currently impounded behind a dam.
Notes
- PWA 2008 provides an analysis of restoration feasibility.
- The lake is currently under public ownership and managed by the General Services Administration.
- CLAMP 2009 describes the final steering committee recommendation to restore the lake to an estuary.
- The Capital Lake Improvement and Protection Association has organized resitance to restoration.
- PSNERP has prepared a preliminary conceptual design for restoration as part of a USACE General Investigation.
- The Deschutes Estuary Restoration Team advocates for restoration of Capitol Lake to an estuary and has assembled historical documents on their website.
- The Squaxin Tribe, also advocating for estuary restoration, provides some information.
