Excellent article/overview of non-point-source pollution from Center for American Progress. Excellent data on types of pollution, EPA regulatory history (or lack of it),and an excellent case study of the Maumee River and its effect on Lake Erie:
The Maumee River and Lake Erie have significant pollution challenges, including high nutrient and sediment levels as well as large hypoxic zones. According to the Ohio Environmental Protection Agency (Ohio EPA), the Maumee River is listed as impaired for drinking water, aquatic life, fish and shellfish consumption, and recreation.44 The river contains high levels of salts, polychlorinated biphenyls (PCBs), nitrogen and phosphorous, sediment, algae, and bacteria.45 These pollutants come from a combination of sources, including active and abandoned industrial sites, municipal sewage discharges, farms and animal feed lots, broken septic systems, and storm runoff carrying salts used to de-ice roads, among other sources.
Nutrient and sediment pollution are especially challenging. According to research by the Ohio EPA, the Maumee River watershed releases more than 2,200 metric tons of phosphorous into Lake Erie each year.46 A 2019 assessment of Lake Erie found that the lake received 11,362 metric tons of phosphorus in that year.47
Heavy nutrient loading has resulted in dangerous algal blooms in the Western Basin of Lake Erie. Approximately 500,000 residents of the city of Toledo and other communities in Northwest Ohio obtain their drinking water from an intake pipe located a few miles offshore in Lake Erie.48 In 2014, Lake Erie experienced a massive cyanobacteria algae bloom.49 Around 1:20 a.m. on August 2, the city of Toledo posted on its Facebook page an urgent message telling residents not to consume or even come in contact with city water until further notice.