Koshkonong Creek Study

Dam Removal Bio Data Lacking

Dam removal is a potentially powerful tool for restoring riverine habitats and communities.

However, the effectiveness of this tool is unknown because published data on the effects of dam removal on in-stream biota are lacking.

We investigated the effects of a small dam removal on unionid mussels in Koshkonong Creek, Wisconsin (USA).

Removal of the dam led to mortality both within the former impoundment and in downstream reaches.

Within the former reservoir, mortality rates were extremely high (95%) due to desiccation and exposure.

Koshkonong Creek in south central Wisconsin is a fifth-order warmwater stream draining a 360-km2 catchment. The basin lies in a low-relief glacial outwash plain dominated by agricultural land use.

The Rockdale dam was first constructed as a rock and timber crib in 1848 to run a grain mill, and then was converted to a concrete structure in 1887. The most recent version,
a 3.3-m high concrete run-of-river dam with a fixed crest spillway, was constructed ca. 1925 and created a 42–45-ha impoundment in 2000.

The Wisconsin Department of Natural Resources breached the Rockdale dam on September 12, 2000.