Surface Water Quality and Ecosystem Restoration: Grand Lake St. Mary’s A Case Study

Grand Lake St. Mary’s is a 21-square-mile lake located in northwest Ohio. The health of the lake in recent years has felt the drastic cumulative effects of agricultural runoff, resulting in hypereutrophication of the entire hydrologic system. As the lake’s water quality declined from nutrient loading, dangerous levels of algae microcystin toxin began to emerge endangering the public health and welfare. In 2010 algal blooms were of such a magnitude and duration, that the Ohio Environmental Protection Agency was forced to close the lake to all recreational activity. The lake was on the verge of a functional breakdown and ecological collapse.A strategic plan was formulated to provide a framework and timeline for restoration of the lake ecosystem utilizing nutrient management, control and removal projects and economic management tools. The Prairie Creek Treatment Train and associated Prairie Creek Littoral Wetland was the first large-scale restoration system implemented as part of the ongoing lake restoration. Further system elements based on these are being planned throughout the lake.