One of the focal events motivating the passage of the Clean Water Act in 1972 was the decline of water quality in Lake Erie, which was originally linked to insufficient treatment of wastewater in some of the biggest adjacent urban centers. The passing of the CWA and the adoption of the Great Lakes Water Quality Agreement in the early 1970s contributed to the quick improvement of water quality in the two ensuing decades, but the 1990s saw the return of water quality problems, indicated by the return of algal blooms to Western Lake Erie. Algal blooms typically occur when excess nutrients are produced by mixture of agricultural and urban practices, and they may threaten ecological stability and public health for millions dependent on the lake for drinking water, tourism, and fisheries. In this case study, we explore the relationship between human behavior and water quality impairments that lead to harmful algal blooms (HABs) in the Western Lake Erie Basin (WLEB), and in particular, the Maumee River Watershed. The case is designed to be taught in eight class meetings to an audience of upper-level undergraduate students, and has been tested in the classroom in consecutive semesters starting in the fall of 2015.