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WINCHESTER LAKE, LEWIS COUNTY, IDAHO - WATER QUALITY STATUS REPORT, 1985
Description:
Winchester Lake, Idaho (17060306) is an 85 acre recreation site located approximately 30 miles southeast of Lewiston. Citizen complaints of poor water clarity, odors, and decline in angler success led to a 6 month study of the lakes water quality in 1985. Winchester Lake exhibits many symptoms of severe eutrophy. Anaerobic conditions and high temperatures were prevalent throughout much of the water column during summer. Mean total phosphate concentrations (with 19% as dissolved orthophosphate) in the euphotic zone were 6 times the recommended limits for reservoirs. The ratio of lake depth to hydraulic retention time was over 10 times the rate considered indicative of eutrophic loading. Phosphorus loading rate by the primary tributary was nearly 2 ? times the rate suggested as critical. Influent inorganic nitrogen concentrations were between 2 and 28 times critical values. The mean chlorophyll a concentration was 6-12 times that considered representative of eutrophic conditions. Neither inorganic metals nor organic compounds (herbicides and pesticides) were found to exceed criteria established for water and fish flesh. Moeller, J.R. 1986. Water Quality Status Report No. 61. Idaho Department of Health and Welfare, Water Quality Bureau, Boise, ID. 56 pp.