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SURFACE WATER RESOURCES

Surface water resources constitute an extremely valuable part of the natural resource base of Waukesha County. Surface waters are a focal point of water-related recreational activities and provide an attractive setting for properly planned resi¬dential development. Surface waters, particularly the major lakes, also provide substantial economic benefits. Expenditures by boaters and other recrea¬tional users of surface waters benefit the owners of restaurants, grocery and convenience stores, service stations, and sporting goods stores in the County. Lakeshore properties, which generally have high assessed valuations, also serve to enhance the property tax base of the County. In addition, when viewed in the context of open space areas, surface waters greatly enhance the aesthetic and scenic characteristics of the natural environment. Because surface water quality is highly susceptible to deterioration from pollutant runoff, both urban and rural land uses must be carefully managed to achieve a balance between level and extent of use and the maintenance of water quality. Surface water resources in the County consist of lakes, streams, and associated wetlands and floodlands.  See Map(PDF)

Lakes
Major inland lakes are those with a surface area of 50 acres or larger, a size capable of supporting reasonable recreational use with minimal degradation of the resource.  Waukesha County contains all or portions of 33 major lakes with a combined surface area of approximately 14,000 acres, or 21.9 square miles, or about 3.8% of the total area of the County.  This represents about 38% of the combined surface area of the 101 major lakes in the seven-county Southeastern Wisconsin Region, more than any other county in the Region.  Thirty of the major lakes are located entirely within the County, while three major lakes, Lake Denoon, Golden Lake, and Lake Five, are located only partially within the County.

In addition to the major lakes, there are 47 other named water bodies with lake characteristics referenced in the DNR publication, “Wisconsin Lakes”, PUBL-FM-800 91.  The lakes of Waukesha County are presented here (PDF).

Because lake water quality is significantly affected by surrounding land use and cover, urban development and agricultural activity on land that drains into lakes and streams has led to a decline in water quality on many lakes in Waukesha County.  Water quality often changes as a result of increasing levels of such nutrients as nitrogen and phosphorous entering the lake.  Nitrogen is usually the limiting nutrient for rooted aquatic plants while phosphorous is considered the limiting nutrient for algae growth.  Eutrophication is the condition reached by lakes when the accumulation of nutrients produces increasing amounts of aquatic plants.  As the resulting lush aquatic plant growth dies each year, organic deposits fill in the lake.  This is a natural process that is generally more prevalent in warm, shallow lakes, such as Big Muskego Lake, than in colder, deeper lakes, such as Oconomowoc Lake.  However, the process can be greatly accelerated by additional nutrients from inadequate or failing onsite sewage disposal systems, lawn fertilizers and animal wastes, construction site runoff, and street debris.

The trophic state serves as an indicator of overall water quality, taking into consideration water clarity, phosphorous content, algae content, and regional location in Wisconsin.  In some cases, the current lake trophic state is a combination of two (i.e. Meso-eutrophic).

A mesotrophic lake shows some signs of eutrophication.  The presence of a greater amount of nutrients than in an oligotrophic lake results in lowered clarity and the presence of aquatic plants.  Swimming and boating can be enjoyed on this type of lake without limitations.

A eutrophic lake has relatively large amounts of aquatic plants because of higher nutrient levels. The water may be cloudy because of suspended algae cells, dying plants may produce unpleasant smells, and mats of plants may interfere with swimming and boating. These lakes are generally shallow, with mucky bottoms. Eutrophic lakes can be excellent warm-water fishing lakes for such fish as bass and bluegills.

 All surface waters in the state of Wisconsin can be classified into one of several biological use objectives classification categories.   The classification categories include:

Cold Water Communities (COLD):  Includes surface waters capable of supporting a community of cold water fish and other aquatic life or serving as a spawning area for cold water fish species.

Warm Water Sport Fish Communities (WWSF):  Includes surface waters capable of supporting a community of warm water sport fish or serving as a spawning area for warm water sport fish.  This category is the default listing for all streams that have not been formally classified according to the process outlined in meeting the federal Clean Water Act goals.  Is also the equivalent of full fish and aquatic waters (FAL) classification.

Warm Water Forage Fish Communities (WWFF):  Includes surface waters capable of supporting an abundant diverse community of forage fish and other aquatic life.

Limited Forage Fishery (LFF):  Includes surface waters of limited capacity because of low flow, naturally poor water quality or poor habitat.  These surface waters are capable of supporting only a limited community of forage fish and aquatic life.

Limited Aquatic Life (LAL):  Includes surface waters severely limited because of very low or intermittent flow and naturally poor water quality or poor habitat.  These surface waters are capable of supporting only a limited community of aquatic life.

Rivers & Streams
Major streams are perennial streams, which maintain, at a minimum, a small contiguous flow throughout the year except under unusual drought conditions.  Waukesha County has approximately 306 miles of major perennial streams.  The longest major stream s in the County are the Fox (Illinois) and Bark Rivers, with 50.6 and 29.7 stream miles respectively, as measured using the County Land Information System.  The rivers and streams of Waukesha County are presented here (PDF).

Outstanding and Exceptional Resource Waters
Chapter NR 102 of the Wisconsin Administrative Code lists water quality standards for all surface waters in the state of Wisconsin.  The two highest classification categories are Outstanding Resource Waters (ORW) and Exceptional Resource Waters (ERW). 

An outstanding resource water (ORW) is defined as a lake or stream which has excellent water quality, high recreational and aesthetic value, high quality fishing, and is free from point source or nonpoint source pollution.  The only outstanding resource water in Waukesha County is Spring Lake.

An exceptional resource water (ERW) is defined as surface waters which exhibits the same high quality resource values as outstanding resource waters, but which may be impacted by point source pollution or have the potential for future discharge from a small sewer community.  Exceptional resource waters found in Waukesha County include specific portions of the following streams:

 Genesee Creek  (Above STH 59)
 Mukwonago River (From Eagle Springs Lake to Upper Phantom Lake)
 Oconomowoc River (From below North Lake to Okauchee Lake)