WATERSHED DESCRIPTION – The area of land that drains to a lake, river or stream. The term “drainage basin” may be also be used interchangeably. A Watershed may be of any size and can be broken down into “sub-watersheds”.
THE PEWAUKEE LAKE WATERSHED – The Pewaukee Lake Watershed currently contains approximately 15,729 acres of total drainage area. 8,249 acres directly drain to the lake. The ratio of the watershed to the lake is approximately 6:1.
SHORELINE – The shoreline or perimeter of the lake is approximately 12.8 miles long. The lake has a development factor of 1.85. This means we have 1.85 times more of shoreline than a lake the same size that is round. If we took an average depth of a lake lot of 300 feet, the total riparian acreage is 415 acres.
HYDROLOGICAL BUDGET – Surface water from the watershed is 70% of the inflow to the lake on an annual basis. The remaining 30% is from natural springs and the precipitation that falls directly into the lake. The time it takes to change all the water in the lake is 1.8 years.
POINT SOURCE POLLUTION – Point source pollution into the watershed is pollution that is associated with a single defined point, such as discharge from a pipe from a factory or sewage treatment plant.
NON-POINT SOURCE POLLUTION – Non-Point source pollution cannot be traced to a single point. This type of pollution would include such things as: Sediment from construction sites and farm fields, sand and salt from highways, fertilizers, pesticides and herbicides from residential and agricultural sources.
POLLUTANTS AFFECTING STORMWATER QUALITY – The most typical sources of pollutants are heavy metals such as zinc, lead, cadmium and chromium. The heavy metals typically come from streets and runoff from impervious surfaces. Along with this runoff also comes litter such as cigarette butts, wrappers, plastics and aluminum.
The most typical nutrients are phosphorus and nitrates. These sources come from leaves and lawn clippings, fertilizer, animal wastes and leaky sewer systems or failing septic systems. The nutrients promote algae blooms and excessive aquatic p[ant growth. For more information go to the EPA’s Storm Water Pollution fact sheet at: http://www.epa.sa.gov.au/xstd_files/Water/Information%20sheet/water_general.pdf
Phosphorus can be found in the soil around the lake and in the bottom sediments. Aquatic vegetation thrives on nutrients so removing the plants themselves help decrease the nutrient loadings in the lake which in turn decreases the potential for large toxic and non-toxic algae blooms to occur.
WATERSHED PROTECTION – How did we start protecting our watershed? In 1990 the District’s Advisory Committee, after discussing long term water quality protection measures, recommended that a wetland purchase program be started. The goal of the program was to purchase a minimum of 350 acres of the most critical wetlands that are filtering pollutants before they reach the lake. An ultimate goal is closer to 600 acres which includes lands that buffer the critical inlet streams that drain into the lake filtering pollutants and providing spawning habitat for the fisheries. The Advisory committee decided that putting these wetlands into protective ownership would be the safest and most likely the only way to assure these wetlands do not become degraded by construction, filling or mitigation and development.
Purchase by the district gave us the ability to begin restoration and improvement projects and as a property owner, the District has the right to take legal action against anyone upstream that is degrading the water quality on our land. The main purpose of the wetland purchase program was to provide water quality protection for Pewaukee Lake.
Power Point presentation (converted to a pdf due to file size): THE-WATERSHED-IT-ALL-RUNS-DOWN-HILL