The Ashippun River watershed lies in Dodge, Washington and Waukesha counties. Its tributaries include Mud Run, Dawson Creek and Davey Creek - a tributary to the Rock River.
Agriculture is the primary land use.
These two documents indicate that polluted runoff may be degrading water quality in the watershed, but monitoring is needed to identify problems and sources. The only municipal wastewater discharger in the watershed is the Town of Ashippun. The water is stained light brown by tannic acid and the bottom is largely silt. An impoundment at Monterey and several structures upstream have created water and fishery qualities similar to those of a lake. Northern pike and bass offer limited fishing.