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Rock Lake, Jefferson County, WI
Rock Lake is a freshwater lake located in the city of Lake Mills within Jefferson County in southeastern Wisconsin, approximately 32.187 kilometers east of Madison.

Geography
The lake was naturally formed by glacial drift and depression in the ground moraine and is one of the four lakes in the Rock Lake watershed. The Rock Lake watershed is 37.0799 square kilometers in area with a main inlet on it's southern side, and is located within the Crawfish River Sub-Basin of the Upper Rock Basin that drains into the Rock River. Rock Lake is now considered to be a drainage lake fed mainly by stream drainage with additional inflows from groundwater, runoffs, and precipitation.

Rock Lake is mesotrophic, which means overall water quality is clear and there is an intermediate rate of bio-productivity and nutrients. There is a wetland on the south end of Rock Lake which hosts a diverse population of organisms and microorganisms within it. Rock Lake has a metalimnetic layer around 7-10 m below the lake's surface, a little deeper than the average of 5m that has been found most suitable for life in freshwater lakes. The lake is mesotrophic, considered to have a moderate amount of dissolved nutrients within in, due to depletion of the hypolimnetic oxygen supply and has a measured secchi dish depth at 4.298 m. The pH of Rock Lake has been found to be roughly 7, which is very suitable for a freshwater lake. A total alkalinity of 190 mg/L defines the lake as having Hard Water, based on its dissolved calcium and magnesium contents.

Habitat
The Lake is considered to be a diverse wetland habitat and classified as a Northern Tamarack Swamp by the Wisconsin Department of Natural Resources based on its moderately mineotropic soil and a canopy dominated by conifers or Wisconsin's native tamaracks. The wetland community surrounding the lake, considered to be mixed shrub carr, sedge meadow, and shallow marsh, occupies the region between the open wetlands near the water and the forested wetlands farther off the shoreline. Many native and migratory birds and waterfowl inhabit these wetlands, including ; Coots, Mallards, Canada Geese, Buffelhead, Canvasback, Ring Necked Ducks, and Tundra Swans. As well as the birds, Rock Lake plays host to a variety of fish species including; Walleye, Yellow Perch, Largemouth and Smallmouth Bass, Panfish, Northern Pike, and Northern Carp.

History & Origin
During the 1830’s, European settlers began living around Rock Lake, in what eventually became Lake Mills. A dam was built in the early 1800s which raised the water level by 10 feet. Around the time of these early settlers, the ecosystem was mainly oak savanna but would eventually be turned into farm land for various agricultural practices. In 1856, Lake Mills was incorporated as a village and turned into a city in 1905. Increases in population and in tourism have provided economic income to the city, which continues to boast a variety of lakeside resorts and inns tailored for the summer tourism season. However, increasing agricultural production in close proximity to the lake has led to an increase in sediment and nutrient offloads into the lake.

Pollution Control
Due to high agricultural runoff from nearby fields, Rock Lake has an increased level of nutrient runoff compared to similar lakes in the Southern Wisconsin area. To combat these increasing contaminant and pollutant levels, Wisconsin Legislators created the Nonpoint Source Water Pollution Abatement Program almost 20 years ago. Nonpoint source pollution encompasses different pollutants that do not necessarily originate from a distinct source but rather from multiple sources, in this instance relating to the agricultural industry surrounding the lake, that serve to diffuse the pollutants across a large area. Rock Lake was named as a lake of priority designation to the program in 1995, with focus on the lake's 12 square mile watershed area. This watershed, and the land use activities that occur within it, drains directly to the lake and thus greatly impacts the lake's overall water quality. Because of it's classification as a drainage lake, some variation in water quality due to runoff and anthropogenic factors can be expected but not at the levels with which Rock Lake was experiencing before precautions were taken.

Conservation
DNR and city officials implemented various rules and regulations in an effort to prevent the water quality of Rock Lake from slipping due to anthropogenic and agricultural contamination. In addition to joining the Nonpoint Source Water Pollution Abatement Program as a priority waterbody, recreational rules are posted visibly around the lake for people to see. Preventing the transportation of invasive species has become a top priority for the lake, and so the inspection, removal, and disposal of all potentially invasive organisms is required before a boat or watercraft can enter the lake. Boat launch areas, no- wake areas, and vessel speed and sound restrictions were all introduced to lake- goers in an effort to conserve and preserve the natural biota and watershed's ecosystem. Rock Lake has long dealt with sediment and erosion control issues due to the level of private and commercial development around the lake. Usually by dredging or excavation techniques, potentially contaminated sediment is removed from the lake to reduce risks to human health or the environment. Because these excavations may disturb aquatic ecosystems in their immediate aftermath, all sediment control and removal for Rock Lake must be reviewed and approved before it may begin. Of particular interest to sediment control in Rock Lake is the Miljala Channel located on it's Western shore. A detailed and encompassing watershed drainage management plan was composed for the town of Lake Mills by the Department of Natural Resources describing a planning- level approach suitable for the management of nonpoint source sediment, bacteria, and phosphorus loads to the channel and the lake. Because the Miljala channel receives drainage from an agricultural ditch and has a watershed of 177 square acres encompassing agricultural fields, state lands, and residential residences, it's protection is vital for the overall health of water quality of Rock Lake itself.

Recreation
Rock Lake itself has four boat docks and two public beaches. Popular as a spot for angler fishing because of the large diversity in fish and biota within the lake, Rock Lake also attracts water and outdoor enthusiasts for other recreation activities such as boating, waterskiing, and ice fishing. The 84 km long and widely popular Glacial Drumlin State Trail runs alongside the lake at various points along it's route between Cottage Grove and Waukesha.

An interesting additional attraction to Rock Lake lies beneath its surface in the form of various pyramidal structures resembling those built 5km to the east at Aztalan State Park in Aztalan, Wisconsin. The pyramids at Aztalan are thought to have been built by the Mississippian culture and is a speculated northern outpost of Cahokia, a much larger Native American city in present day Illinois. Divers, archaeologists, and historians form all over the United States have come to study and survey Rock Lake because of these mysterious pyramids.

Beaches and Boating
The two public beaches on the Southeast side of the lake. Sandy Beach has a boat launch while Bartel's beach does not. Other public boat launches are located in the Ferry park landing access, Elm Point Rock Lake access, and North End launch Park Lane Rd.

The daily fee for accessing the boat launch is $7.00 daily and $40.00 annually.