Dell Creek is a warm freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

 that lies in northeastern Sauk County

Sauk County, Wisconsin

Sauk County is a county in the U.S. state of Wisconsin. As of 2000, the population was 55,225. Its county seat and largest city is Baraboo. Sauk County is included in the Baraboo Micropolitan Statistical Area and in the Madison Combined Statistical Area....

 and southern Juneau County

Juneau County, Wisconsin

Juneau County is a county located in the U.S. state of Wisconsin. As of the 2000 census, the population was 24,316. Its county seat is Mauston. It should not, however, be confused with the city of Juneau, Wisconsin, to which it has no connection.-Geography:...

 in central Wisconsin

Wisconsin

Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

. The area along the stream is
hilly with nearby intensive agriculture. Dell Creek is a warm water sport fishery for the lower 1.5 miles and a Class II trout stream for
the upper 10.5 miles of its length. The creek is classified as an exceptional resource water. Much of Dell Creek's length in Sauk County is publicly owned.

The main problems on the creek are sediment and nutrient loading from agricultural sources and a lack of in-stream habitat. Surveys conducted in 1995 found low numbers of trout and
determined the water quality to be from fair to poor in some locations. This indicates that the
stream has experienced some severe environmental damage. It is thought that the limited
habitat is one of the limiting factors for aquatic life.

There are also two large impoundment

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

s on Dell Creek. One creates Lake Delton

Lake Delton

Lake Delton is a man-made freshwater lake in Sauk County in central Wisconsin. For much of 2008, it was a mostly empty lake basin after a portion of a county highway that forms part of the dike wall eroded on June 9, 2008, under the pressure of floods in the area. The resulting washout caused the...

 and the other creates Mirror Lake

Mirror Lake State Park

Mirror Lake State Park is a Wisconsin state park in the Wisconsin Dells region. It contains Mirror Lake, a narrow reservoir with steep sandstone sides up to tall. The lake has a surface area of and an average depth of . Recessed out of the wind, the water of Mirror Lake is usually calm and...

. Silt and sediment from farm fields are thought to be a problem in the
stream and are causing a sediment problem in the upper end of Mirror Lake. Suspected high
nutrient inputs to Mirror Lake from Dell Creek are thought to be fueling the excessive aquatic
plant and algae growth in the lake.