Wisconsin Ecological Services Field Office

Midwest Region


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2661 Scott Tower Drive
Green Bay, WI 54229-9565
Phone: 920-866-1717
Fax: 920-866-1710
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e-mail: GreenBay@fws.gov


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Hydropower Planning

Prairie du Sac Hydropower Dam and Fishway


Biologist showing a large paddlefish.

The Prairie du Sac Dam currently blocks fish, like the paddlefish, from moving upstream of the dam.

Photo by USFWS

Wisconsin Power and Light Company (a subsidiary of Alliant Energy Corporation) is the owner and operator of the Prairie du Sac Hydroelectric Dam located on the Wisconsin River near the village of Prairie du Sac, Wisconsin. A license issued by the Federal Energy Regulatory Commission in 2002 includes a condition that requires the company to provide for fish passage that allows fish to move upstream from below the dam. The dam has been a barrier to upstream fish movement since it was constructed over 100 hundred years ago and the result has been loss of aquatic species upstream of the dam. As part of the effort to restore fish passage at the dam, the U.S. Fish and Wildlife Service started a public scoping effort as we began an Environmental Assessment that describes and evaluates alternatives for providing fish passage. 


June 27, 2013 News Release: Public Invited to Learn More About Fish Passage at Prairie du Sac Dam: Public Open house slated for July 15 in Prairie du Sac


Prairie du Sac Hydropower Dam and Fishway - Frequently Asked Questions


Notice of Intent: Conduct Scoping for an Environmental Assessment of Alternatives for Fish Passage at Prairie du Sac Dam


Wisconsin Power and Light Company Responsibilities

The owner of a hydroelectric dam is required to obtain an operating license from the Federal Energy Regulatory Commission (FERC) pursuant to the Federal Power Act, 16 U.S.C. §§ 791a et seq.


  • State and Federal agencies, as well as the River Alliance of Wisconsin, made formal recommendations during FERC’s hydropower licensing proceeding to have fish passage installed at Prairie du Sac Dam because of the need for fish to migrate to suitable habitat above and below the Prairie du Sac Dam.


  • After FERC issued the license in 2002, the U.S. Fish and Wildlife Service, in close coordination with the Wisconsin Department of Natural Resources, prescribed that FERC require fish passage as part of the operating license pursuant to Section 18 of the Federal Power Act. FERC amended the Prairie Du Sac license to include the U.S. Fish and Wildlife Service’s fish passage prescription.


U.S. Fish and Wildlife Service Responsibilities


  • The U.S. Fish and Wildlife Service is required to review and approve a fishway alternative, as provided by the licensee (Wisconsin Power and Light), for the safe, timely, and effective passage of fish at Prairie du Sac Dam.  This is a condition of Wisconsin Power and Light's requirement to install fish passage at Prairie du Sac Dam.


Developing and Selecting Alternative for Fish Passage


  • Environmental Assessment
    Due to concern that a fishway would allow invasive species such as Asian carp (Hypophthalmichthys spp.) to spread upstream of the dam in the Wisconsin River and its tributaries, the U.S. Fish and Wildlife Service decided to prepare an Environmental Assessment to evaluate the environmental consequences of fish passage alternatives in accordance with the National Environmental Policy Act (NEPA). Using this process will ensure that practical alternatives are adequately evaluated and considered before approving a final alternative.


  • Public Scoping Meeting and Comment Period
    The U.S. Fish and Wildlife Service hosted an Open House and opened a public comment period to allow interested parties a voice in identifying alternatives and concerns. This open house and comment period were part of a formal scoping process for the Environmental Assessment of alternatives for fish passage at Prairie du Sac Dam. During the public comment period we asked interested parties to provide us information on issues, concerns, or data that should be considered in the Environmental Assessment. The public comment period for scoping closed August 1, 2013.

Criteria for Fish Passage Alternatives

We need to select an alternative that complies with any conditions stated within Wisconsin Power and Lights license to operate the Prairie du Sac Hydroelectric Dam, such as conditions stated in their Fishway Prescription.  The alternative also needs to comply with all applicable laws, such as restrictions on movement of invasive non-native species.


  • An alternative that provides safe passage, meaning it will not cause significant injury or death to fish passing the dam.


  • An alternative that will provide timely passage, meaning it will function each year during appropriate seasons and for a sufficient period of time when fish are attempting to pass the dam.  Passage of fish must occur within appropriate seasons to avoid or minimize delayed movements and must help fish complete their life cycle within, sometimes, narrow environmental conditions (e.g., specific temperatures and flow rates).


  • An alternative that will provide effective passage, meaning it will provide passage for native fish that want to move upstream and downstream of the dam, but will not allow fish considered invasive or deleterious to move upstream of the dam.



  • An alternative that complies with all applicable State and Federal laws, including any requirements contained within the Prairie du Sac Dam’s operating license issued by FERC, including the fishway prescription.


U.S. Fish and Wildlife Service, Wisconsin DNR and River Alliance Reasons for Fish Passage

Two Higgins eye pearlymussels shown in the palm of a hand.

Before the dam was constructed, the Higgins eye pearlymussel was likely found in the Wisconsin River upstream of Prairie du Sac.

Photo by USFWS


The Prairie du Sac Dam is the first barrier on the Wisconsin River upstream from its confluence with the Mississippi River and it creates a complete barrier to fish movement. Many fish need access to upstream habitats seasonally as a necessary part of their life cycle and mussels use fish as a means of moving into upstream river reaches. As a result of the Prairie du Sac dam blocking fish passage, there are 19 species of fish and 15 taxa of mussels that were present (or presumed to be present) in the Wisconsin River upstream of Prairie du Sac before the dam was built but are no longer present between Prairie du Sac Dam and Kilbourn Dam (the next dam upstream).


“Fish Passage” and "Fishway" Defined


  • Dams typically act as barriers to the movement (or passage) of fish in rivers especially in cases where the dam is much too tall for the fish to “jump” over, such as with the Prairie du Sac Dam.


  • Because the Prairie du Sac Dam acts as a complete barrier to upstream fish passage, it is necessary to find a way to allow these fish to “bypass” the dam, such as through a fishway. 


  • A fishway is an engineered structure that provides a means for fish passage around a dam. A fishway is a compromise between the need for power production and the need to get fish past a dam so they can access upstream river reaches.


  • A fishway must be designed in a way to allow for the safe, timely and effective passage of fish upstream and downstream around the dam.


  • Follow this link to an external website from the government of New South Wales Australia (not affiliated with this project or the U.S. Fish and Wildlife Service) that does a good job describing each common type of fishway.


Additional Information





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Last updated: June 28, 2019