Soo Locks Fish Habitat Restoration

Sault Ste. Marie, Michigan, United States

The Soo Locks project is an example of integrating Engineering With Nature (EWN) practices and principles with U.S. Army Corps of Engineers (USACE) water operations activities. The flow out of Lake Superior is controlled by man-made water retention structures that form a dam across the head of the St. Marys River, controlled by Compensating (Comp) Works gates. Immediately downstream of the gates, the St Marys Rapids is approximately 28 hectares of large rock substrate and fast-flowing water habitat. Comp works gate position adjustments have historically been made using manual cranks, resulting in quick gate position adjustments, causing flow rates and water levels in the Rapids to change abruptly, negatively impacting fish habitat by stranding fish when gates are closed and flushing out eggs and fry when gates are opened. This project, implemented by USACE Detroit District, modeled the local hydrodynamics of the river so that automation of four of the Comp Works gates via electric motors can be optimized to improve fish habitat immediately downstream; the automation of the gates is scheduled to be completed by 2018.

Article cover: The old Compensating Works gate motors built 100 years ago are manually operated and cause rapid changes in water levels, reducing the quality of the fishery habitat in the St. Marys Rapids downstream. (Photo by Justin Wilkens, ERDC)

Producing Efficiencies

This gate automation will result in gradual gate position adjustments over longer periods of time, yielding more measured fluctuations in flow rates and water level elevations. Gate adjustments currently made over the course of 10 minutes would be made over the course of hours or days, which will more closely mimic natural fluctuations in flow rates and enhance fish habitat. Ecosystem responses to the hydraulic conditions in this area is a critical component of the evaluation of water level regulation plans for the upper Great Lakes system and will enable USACE to manage the resource adaptively.

Using Natural Processes

Optimizing gate operations to improve marginal riverine habitat is a cost-effective and efficient means of increasing suitable habitat for a wide variety of fish. The St. Marys Rapids provide critical spawning, rearing, and feeding habitat for many macroinvertebrate and fish species. Native whitefish, lake sturgeon, trout, perch, and pike, along with recently introduced salmon species occur here, making this a world-class fishery, and also one of the top fly fishing destinations in North America. Thus, the project is of local, regional, and trans-boundary significance, with widespread applicability across many lock and dam structures owned by the USACE.

The St. Marys Rapids consist of a variety of substrate types that provide habitat for numerous species of fish, as well as for birds and waterfowl.

(Photo by Justin Wilkens, ERDC)

Broadening Benefits

The project—automating the Comp Works gates along the U.S. side—will maximize habitat value of the rapids while maintaining other USACE regulation plan objectives. The improvement in the regulation of water through the Comp Works will improve the river rapids habitat for Lake Sturgeon and multiple other warm- and coldwater fish species that have been negatively impacted by habitat loss in the St. Marys River. Recreational fishing in the St Marys River is a year-round industry for the local area, and enhancing fish habitat will keep that industry—and the other industries associated with it—viable as well, yielding numerous economic and social benefits.

Permanent EWN displays are positioned on the observation platform of the Soo Locks Visitors Center, which attracts up to 500,000 visitors each year.

(Photo by Justin Wilkens, ERDC)

Promoting Collaboration

Ecosystem responses to the hydraulic conditions in this area is a critical component of the evaluation of water level regulation plans for the upper Great Lakes system and will enable the USACE to manage the resource adaptively. The project is of local, regional, and transboundary significance, and includes stakeholders from the U.S. Geological Survey, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, Great Lakes Fisheries Commission, St. Marys River Fisheries Task Group, Michigan Department of Natural Resources, Lake Superior Water Control Board, Ontario Ministry of Natural Resources and Fisheries, and Lake Superior State University.

Roughly 7,000 vessels hauling 86 million tons of cargo pass through the Soo Locks annually. Soo Locks provide the connection between Lake Superior and the Lower Great Lakes.

(Photo courtesy of Michelle Briggs, USACE)