Diversion of Wastewaters from Madison Lakes

In general, an improvement in water quality of the Madison, Wisconsin, lakes resulted after sewage effluent was diverted from them. This was evidenced by a reduction in the phosphorus content of the lakes as well as a decrease in the frequency and severity of blue-green algal blooms. Based on the limited data available, the rate of response of two relatively small and shallow Madison lakes, Lake Waubesa and Lake Kegonsa, following a reduced phosphorus influx (the result of a major sewage diversion in 1958) was found to be similar to that predicted from a simple, exponential decay model based on the hydraulic residence time. It is predicted based on a phosphorus residence time that a new equilibrium phosphorus content will be reached in Lake Mendota in about 1975, or about three years following the reduction in the phosphorus resulting from the wastewater diversion.