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Water quality trends in Lake Simcoe, 1972-1990

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Title: Water quality trends in Lake Simcoe, 1972-1990
Author: Nicholls, K. H.
Abstract: An overview of recent limnological findings is presented with emphasis on the long-term record of dissolved oxygen, nutrients, phytoplankton, and chloride trends for Lake Simcoe. The main sampling efforts have included visits to 10-12 sites every 2-3 weeks during the May-October periods and weekly, year-round collections of nearshore samples from four municipal water supply intakes. Major improvements in water quality have not yet occurred in response to nutrient loading controls initiated during the last two decades. However, there is some evidence of lower total phosphorus concentrations at all lake locations during the late 1980s. Phosphorus release from anoxic bottom sediments during late summer may retard recovery of the lake. The rate of increase of chloride in the Lake Simcoe outflow and in samples collected from municipal water supply intakes averaged 0.4-0.6 mg/L/yr over the past 20 years and likely reflects expanding urbanization in the Lake Simcoe basin. Some thoughts on future surveillance, research and planning needs are also presented.
Date: 1992
Rights: Queen's Printer for Ontario, Crown Copyright, Non-Commercial Use Permitted
Rights Holder: Queen's Printer for Ontario
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