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|