Unlike lakes that are polluted by industrial pipes or sewage inflows, Lake Wingra has no major points of pollution. Instead, lake pollution is a result of the small amounts of pollutants picked up from all over the watershed. This is called non-point source pollution. Swimming Beach Closures Beaches are closed when bacteria counts are high enough to potentially cause illness. The bacteria sampled, such as e. coli or fecal coliform, may have increased due to wastes from ducks, swimmers, or pet waste washed in to the lake by stormwater.
Algae blooms contribute to beach closures in that blooms are a good place for bacteria to grow.
The lake is not very clear because the bottom is frequently stirred up. This condition, known as turbidity, is a result of fine sediments brought in from the watershed by stormwater, and their constant resuspension by carp. Weeds Aquatic plants, while natural in Lake Wingra, have been a problem in the past. Milfoil, a non-native pond weed, invaded Lake Wingra and was able to grow so much that it caused problems for boats and smelled bad. Natural processes now limit weeds in Lake Wingra to a level considered close to normal.