Project completion summary of the effects of restoration procedures at liberty lake, washington

Abstract

The implementation phase of the Liberty Lake restoration project included construction of marsh flushing controls, dredging of 21 ha of the lake bottom, and treatment of the lake waters with aluminum sulfate. This work was started in November 1979 and completed in May 1981. After four years of postrestoration water quality monitoring nutrient levels in the lake and inflowing waters have been reduced, and the trophic state has declined toward a more mesotrophic condition. Comparison of pre- and postrestoration nutrient budgets indicates that a reduction in phosphorus loading of 34 percent was achieved. It appears that the sewering was primarily responsible for this reduction. Although the desired change in the phytoplankton community (from primarily blue-green to primarily green algae) did not occur, indications are that long-term productivity and incidence of blue-green blooms has been significantly reduced. In addition, if the restoration had not been done when it was, water quality in Liberty Lake would have been severely degraded because of high flood flows and nutrient loading through the marsh system. The realized benefits of, and problems with, the individual efforts involved in this multiphased project are documented in the following discussion. © 1986 Taylor and Francis Group, LLC.