Lake Koshkonong is a reservoir in southern Wisconsin, which was transformed from its original marshland by the construction of the Indianford Dam in 1932. The lake lies along the Rock River, with the river acting as both the primary inflow and the primary outflow for the lake. Lake Koshkonong begins downriver from Fort Atkinson, with the large majority of the lake located in southwestern Jefferson County. Small portions of the lake extend into southeastern Dane and northern Rock counties.

After the creation of the Indianford Dam, which was built several miles down the Rock River from Lake Koshkonong, the lake gained a surface area measuring . It remains very shallow with an average depth of and a maximum depth of . The dam itself measures high and with a length of at its crest. Maximum capacity of the reservoir is . Both dam and reservoir are owned and operated by Rock County.

History and etymology

The currently accepted spelling "Koshkonong" was first used by James Duane Doty in 1844. An often repeated claim that has been recently disputed is that the meaning of the name is "the lake that we live on". A more accurate approximation may be "where there is heavy fog," or "where it is closed in by fog". Current thinking suggests that the modern spelling is a contraction of various names given to the region by white settlers in the early 19th century. They incorporated various pronunciations of the region from various surrounding tribes, including "Kashkawanung" from the Ojibwe, "Coscahoenah" from the Menominee, and "Kuskouonog" from the Potawatomi. This theory is supported by the fact that these name forms seem to share Algonquian language patterns, despite describing a Ho-Chunk (Siouan) village. More evidence disputing the older name translation is that the name seems to have described a Winnebago village on the shores of the lake, with the name being extended to the body of water at a later date.

This spelling of the lake's name gained legitimacy after surveying efforts in the area codified this interpretation in the 1830s and 40s. Fort Koshkonong, a fort of some importance to the United States during the Black Hawk War, was named in accordance with this convention. The fort was active before the Rock River was dammed, when the area was a cattail marsh with the Rock River running through the middle. Today, the lake borders the towns of Koshkonong on its eastern side and Sumner on its northern side.

Ecology

Vegetation

Lake Koshkonong has seen many vegetational changes in the past 150 years. Once a deep-water marsh covered with emergent vegetation, the lake was predominantly wetlands filled with reeds, wild rice, and grasses. The wetlands have significantly disappeared since then due to rising water levels caused by higher dams and the ever changing landscape. It is estimated to have lost over 100 acres of wetland by 2000. Now, the large pool of water known as Lake Koshkonong has been replaced by lake sedge (Carex lacustris), bur-reed (Sparganium), and other aquatic species. The lake association has been trying to introduce Pondweed and Wild celery to improve fish habitats.

Fish

Throughout the Rock River (Mississippi River tributary) and Lake Koshkonong around sixty species of fish can be found. Many of those species are river spawners, meaning the release of gametes from the body occurs in the rivers even though they might spend their whole life in lakes. Floods and droughts will both affect spawning of different species of fish, enhancing the amount of some and depleting others. A few species of fish that can be found in the lake include muskellunge, panfish, largemouth bass, smallmouth bass, northern pike, walleye and catfish.

Birds

In the surrounding habitats of Lake Koshkonong's riparian wetlands, many endangered species of birds can be found. The rising water levels have an unfortunate impact on these species. Loss of trees, herbaceous vegetation, and groundwater dependent wetland plants will effect the species they support. Some of the rare species found in this area that are impacted by rising water levels and habitat loss are the Cerulean warbler and the Acadian flycatcher. Other rare species of birds that are being affected are Black tern, Forster's tern, American bittern, Least bittern, and Virginia rail. For fishing to be able to occur on the lake it has to be stocked by the Wisconsin Department of Natural Resources at the Bark River Hatchery in Fort Atkinson with Walleye and Northern pike. There are four boat landings around the lake for people to use and also two beaches. Thunder on the Lake is a high speed boat race that has been held on Lake Koshkonong. The boats are hydroplane powered and can reach speeds up to 60 MPH. Other boat races are also held for fishing boats, and other smaller boats. The Venetian Boat Parade is put on by the Rock Koshkonong Business Association. Participants are encouraged to dress up their boat with lights and decorations of their choosing and cruise along with one another ending at the Lakeview bar.

Winter attractions

Ice fishing and ice racing used to be much more common, but due to warmer weather in the past few years the activity has not been as popular. Other winter activities practiced on and around the lake include snowmobiling, fatbike riding, and ice skating. The transparency of the water is low and algal blooms occur frequently, causing this classification. A lake will be classified as hypereutophic if it has more than 40 micrograms/liter of chlorophyll, more than 100 micrograms/liter of phosphorus, and a visibility depth of less than 3 feet. The Trophic State Index scale also helps with these classifications. If a lake scores a TSI of above 50 it will be considered hypereutrophic. Lake Koshkonong has a TSI score of 67.

Proposed nuclear power plant

In the 1970s, Lake Koshkonong was the primary site considered for a billion dollar nuclear power station. Wisconsin Electric Power Company, Wisconsin Power and Light Company, Madison Gas and Electric, and Wisconsin Public Service Corporation jointly proposed the project. They chose Lake Koshkonong out of 84 potential sites because of the solid rock found here that could be used for the foundation, and the Rock River could be used as an adequate water source. In 1974, it was estimated that the utilities would lose $40 million if the two-unit, 900 MW each, facility was not approved. At that time, the timetable had already slipped to a 1983/1984 commissioning. The proposed two pressurized-water reactor system had hopes of beginning construction in 1978.

The plan was met with strong resistance from environmental groups. It was eventually killed in 1977 by concerns regarding the lake's shallow depth and consequences to the plant during drought conditions. Water would have been exiting the lake to cool down the plant, and residents were uneasy about that along with other aspects of the project. The power plant was intended to relocate many residents and disrupt farmland as well. It was estimated that the disruption to farmland would cost farmers a total of $27,500 each year for lost crops.

References

  • Rock Koshkonong Lake District
  • Lake Koshkonong data and
  • Lake Koshkonong Wetland Association
  • Visitor & Tourism | Rock Koshkonong Business Association
  • Historical tidbits about the Lake from the Janesville Gazette
  • Koshkonong - The Lake We Live On