Menomonee River Watershed

The Menomonee River Watershed covers an area of approximately 136 square miles located in Ozaukee, Waukesha, Washington, and Milwaukee Counties. The River begins in Mequon and Germantown, and flows southeast for 32 miles until its confluence with the Milwaukee and Kinnickinnic Rivers. The Menomonee River Watershed is densely populated; its land cover is approximately 67% urban/developed, 11% agriculture, and 12% grassland/forest (WDNR 2016). Only around 9% of the land use within the Menomonee River Watershed is defined as wetland; those wetlands make up around 39% of the 100-foot riparian corridor surrounding the Menomonee River (WDNR 2016).

Historically, to control how water moved through populated stream segments to limit flooding and maximize the space available for the growth of urban and suburban communities, large portions of the Menomonee River were channelized, straightened, lined with concrete, and/or dammed. Around 8% of the 96 stream miles in the Menomonee River Watershed were at one point lined with concrete, and around 36 dams or drop structures and 269 culverts were put in place to manage stream conditions (WDNR 2010). The extensive history of urban and suburban development in the Menomonee River Watershed significantly impacted the function of its streams, destroyed habitat, and disconnected the river from its surrounding lands and wildlife.

Some of the most substantial threats to the Menomonee River include extensive channel modifications that minimize the diversity of aquatic habitats, and increase the amount of runoff that enters the river from impervious surfaces. Straightened and concrete lined channels are designed to quickly move water through a stream to reduce the risk of flooding. However, these alterations also limit the interactions between aquatic communities and habitat that naturally exists along the banks, floodplains, and bends of stream channels. As a result of human modifications and development in the Menomonee River Watershed, many streams are incredibly flashy, and rise drastically during precipitation events, and quickly shift into small or medium sized streams when runoff ceases (WDNR 2010). Changes to flow can limit the diversity of habitat available to organisms that might be better suited for warm slow flowing water, or colder water moving rapidly through a channel, but not both. Dams and culverts also restrict mobility of aquatic organisms as well as particulates traveling the length of the stream, which are essential in constructing different types of stream habitats. The presence of obstructions in the stream limit the ability of native fish and aquatic life to reach available habitat further upstream (WDNR 2010).