Establishing a Chlorophyll a Goal for a Run-of-the-river Reservoir

Lake Pepin, a I 00 km2 run-0f-the-river reservoir, is located on the Mississippi River about 80 km downstream of the Twin Cities metropolitan area on the border between Wisconsin and Minnesota. A major inter-agency study of Lake Pepin and the Mississippi River has been underway since 1990 for the purposes of determining the impacts of the effluent from the Metropolitan Waste Control Commission's Metropolitan Wastewater Treatment Facility on Lake Pepin and to predict the benefits of reducing effluent phosphorus levels to l mg L 1 or lower. Severe nuisance algal blooms and fish kills during the low flows of 1988 prompted this study. Understanding the reservoir limnology and factors contributing to user perception of nuisance a1ga] blooms" (in terms of chlorophyll a concentration or phytoplankton species composition)