The Rock River dam in Beloit was built in 1844 by James Hanchett, a pioneer contractor who had also built dams in Indiana and Illinois (Beloit Historical Society 2005). The Rock River dam is a allows water to flow into and out of the reservoir at the same time. Such dams are called “run-of-the-river” dams and have a small ecological impact (Allan 1995).

There are approximately 80 dams in the Upper Rock River (Wisconsin Department of Natural Resources 2005). Some of these dams are used to generate hydroelectric power and others are serve migratory waterfowl (Wisconsin Department of Natural Resources 2005). There are no flood control dams along the Rock River (Wisconsin Department of Natural Resources 2005).

Dams, though an efficient source of renewable energy, result in harmful physical and biological changes in a river. Water quality changes depend the time that water spends in the reservoirs, whether the dam releases surface or deep water, and how much water evaporates from the reservoir. (Allan 1995). Dams break “upstream-downstream connectivity” of a river, affecting fish migrations (Allan 1995).

The Wisconsin Department of Natural Resources (2005) states that water quality problems in reservoirs on the Upper Rock River are “excessive growth of algae, reduced dissolved oxygen levels, and poor water clarity (turbidity), [are] caused by agricultural and urban polluted runoff, which contribute thousands of tons of sediment and nutrients to surface waters annually.” In general, invertebrate communities immediately below dams show a reduction in species richness, but an increase in overall abundance (Allan 1995). Most of these biological effects cease to be evident some distance down stream depending on dam and river type. It could take as little as 2 km on a tributary river just above the confluence, and as long as 80 km for deep dam release on the mainstream of the river (Allan 1995).

[dam]

The dam across the Rock River in the City of Beloit. Photo by Liz Hart.

[Rock River Dam]

The dam across the Rock River in the City of Beloit. Photo by Liz Hart.

[Rock River Dam]

The dam across the Rock River in the City of Beloit. Photo by Eric Nelson.

Sources:

Allan, David J. Stream Ecology: Structure and function of running waters. Dordrecht: Kluwer Academic Publishers, 1995.

Beloit Historical Society. Hanchett-Bartlett Homestead. The Beloit Historical Society. Accessed 24 Oct. 2005. http://www.ticon.net/~beloiths/hanchett.htm.

Wisconsin Department of Natural Resources. 2005 Upper Rock River Basin Homepage. Last revised 6 Oct. 2005. Accessed 24 Oct. 2005. http://www.dnr.state.wi.us/org/gmu/uprock/.