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Upper Rock River basin

The Upper Rock River basin lies in south-central Wisconsin's eastern ridges. At the north end of the basin, the east, south and west branches of the Rock River come together in Horicon Marsh. From the city of Horicon, on the south edge of the marsh, the river flows south 76 miles to Fort Atkinson.

The remainder of the Rock River mainstem, 62 miles, is in the Lower Rock River basin, which extends from Fort Atkinson to the Wisconsin-Illinois border. The gradient of the Upper Rock River is very flat. The fall of the river from the upper Federal dam in the Horicon National Wildlife Refuge to the upper Watertown dam is just 34 feet over 58 miles.

The basin is bounded on the east by the Niagara escarpment and the eastern terminal moraine, formed by the Green Bay lobe during the last glaciated period in Wisconsin. The most dominant geologic features are the extensive drumlin fields in Dodge County and portions of Dane, Columbia and Jefferson counties.

Water resource information for specific watersheds

Watershed name/view details Watershed size Lists (streams, lakes, bays & harbors) Counties Water management unit (WMU) Major drainage system
Ashippun River 68.7 mi 2 UR10 Water lists Dodge, Jefferson, Washington, Waukesha Upper Rock Mississippi River
Beaver Dam River 290.25 mi 2 UR03 Water lists Columbia, Dodge, Fond du Lac, Green Lake Upper Rock Mississippi River
Calamus Creek 30.18 mi 2 UR04 Water lists Columbia, Dodge Upper Rock Mississippi River
East branch Rock River 198.99 mi 2 UR13 Water lists Dodge, Fond du Lac, Washington Upper Rock Mississippi River
Johnson Creek 45.22 mi 2 UR07 Water lists Jefferson Upper Rock Mississippi River
Lower Crawfish River 177.65 mi 2 UR02 Water lists Columbia, Dane, Dodge, Jefferson Upper Rock Mississippi River
Maunesha River 126.02 mi 2 UR05 Water lists Columbia, Dane, Dodge, Jefferson Upper Rock Mississippi River
Middle Rock River 95.12 mi 2 UR01 Water lists Dodge, Jefferson Upper Rock Mississippi River
Oconomowoc River 130.86 mi 2 UR09 Water lists Dodge, Jefferson, Washington, Waukesha Upper Rock Mississippi River
Rubicon River 79.15 mi 2 UR11 Water lists Dodge, Washington Upper Rock Mississippi River
Sinissippi Lake 234.93 mi 2 UR08 Water lists Dodge, Jefferson, Waukesha Upper Rock Mississippi River
Upper Crawfish River 161.18 mi 2 UR06 Water lists Columbia, Dane, Dodge Upper Rock Mississippi River
Upper Rock River 257.61 mi 2 UR12 Water lists Dodge, Fond du Lac, Green Lake Upper Rock Mississippi River

Maps