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Estimation of phosphorus loadings and evaluation of empirical oxygen models for Lake Simcoe for 1970-1990

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Title: Estimation of phosphorus loadings and evaluation of empirical oxygen models for Lake Simcoe for 1970-1990
Author: Snodgrass, W. J.; Holubeshen, J.
Abstract: This document presents three sets of information which were used in support of modelling studies of dissolved oxygen in Lake Simcoe. Firstly, water balance and phosphorus loading estimates are developed for the period 1970 to 1990. The water balance is summarized in Table 1, the phosphorus loadings in Table 2. Then, a comparison of historical phosphorus loadings is made with sediment accumulations of phosphorus. Finally, an analysis is made of hypolimnetic oxygen depletion rates for the period 1971 to 1985 using an empirical modelling formulation. The hydrological inputs to the lake were estimated from Water Survey of Canada measurements on rivers such as the Holland River, extrapolation of the Water Survey data to downstream areas and to other smaller watersheds, and measurements for WPCPs and rainfall. Evaporation estimates were evaluated as the difference between total inputs and flows out the Lake Simcoe outlet, assuming that insignificant volumes of water are stored in the lake from year to year. Phosphorus loading estimates have been made previously for four years: 1972, 1982, 1983 and 1984. Phosphorus loading estimates for the Black River and Holland River have been made by the Lake Simcoe Conservation Authority for the period 1982 to 1989. The concentration estimates for the Black River which average 0.040 mg/L on an annual basis were extrapolated to provide loading estimates for the remainder of the tributaries. These concentration estimates are approximately one-quarter of the average annual values for the Holland River (0.161 mg/L). Loading estimates for the WPCPs were obtained from records for the period 1985 to 1989 and from previous reports for the Bathe WPCP for the 1972-1980 period. Loading estimates for precipitation, urban runoff and cottages for 1985-1989 are based upon extrapolations. Estimates for 1977-1980 are based upon interpretation of data and are uncertain with respect to whether the levels estimated for 1977-1980 were achieved during this period or earlier in the 1970's.
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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