APPLETON — It’s real easy to explain why the project to restore Marsh Lake is not yet at the finish line.
“A lot of rain, all at the wrong time,” said Clay Tallman, project manager with the U.S. Army Corps of Engineers St. Paul Division.
Tallman also had encouraging news as he led the partners in the nearly $13 million project on a tour of the site Oct. 31. There are only about eight to 10 weeks of work remaining, he said. That work can take place this winter no matter the temperature, but it cannot get underway until water levels decline.
Water levels below the Marsh Lake control structure are about 6 feet higher than typical for this time of year. The high water has kept the project contractor, TRS Shearing, of Jamestown, North Dakota, from completing a fish passage at the lake’s outlet. It’s the last major piece of the ecological restoration project waiting to be completed.
When the levels drop, the contractor will install a series of 12 to 13 boulder arches right where the fixed level dam once stood at the lake’s outlet. Like a stairway, the arches will create small rapids which fish can navigate during any flow level. It will restore connectivity in the riverine system, allowing fish to naturally move between Marsh and Lac qui Parle lakes.
“No project goes without its challenges,” said Colonel Karl Jansen, district commander for the U.S. Army Corps of Engineers St. Paul Division, at the start of the tour. He added that he is confident the passageway can be completed by the spring of 2020.
Along with contending with three of the wettest summers on record, Tallman said the contractor has also had to cope with a worker shortage.
The first milestone occurred when the contractor completed the control structure that replaces the fixed crest dam. And almost exactly one year ago, the contractor breached a levee at the site and restored the Pomme de Terre River to its natural connection with the Minnesota River above the control structure.
The control structure will allow the Minnesota Department of Natural Resources to periodically drawn down Marsh Lake. A draw down will expose mud flats and shoreline areas and allow native vegetation to return. It will also induce winter kill and eliminate the carp that uproot and keep native, aquatic vegetation from taking hold.
Re-establishing the vegetation is critical to restoring Marsh Lake to the days when it was one of the state’s premiere waterfowl destinations. Dave Trauba, regional wildlife manager with the Minnesota Department of Natural Resources in New Ulm, said he remembers times when the lake was so thick with sago pondweed it was impossible to take a motor boat on parts of the lake. The vegetation drew migrating waterfowl to the lake like sports fans to the stadium on game day.
“There should be 50,000 mallards out here,” said Trauba as he gazed over the quiet waters of the lake during the tour. He said the goal will be to allow emergent vegetation to return along the perimeter of the lake, as well as the submergent vegetation such as sago pondweed. This mix of vegetation will provide both food and cover to attract migrating waterfowl.
Shallow lakes evolved during a climate regime of wet and dry years. The periodic draw downs will allow us to mimic this natural cycle, Trauba pointed out.
Changes under the water’s surface will be coming once the fish passage is established. It will allow fish migration throughout the year for all species of fish, according to Chris Domeier, fisheries supervisor with the Minnesota Department of Natural Resources in Ortonville.
The fixed crest dam that maintained the lake level for the past 80 years essentially restricted fish passage to carp, he pointed out. Allowing fish to naturally migrate in and out of the lake to take advantage of food and habitat will make it possible for a variety of fish species to thrive in the lake. It will mean a much greater share of the biomass will be represented by native fish species in place of carp, he explained.
Domeier said returning the Pomme de Terre River to its natural channel has already provided benefits in terms of greater habitat for fish in the system.
The river’s return to its natural channel has come during a high flow period, and that has meant challenges, according to Tallman. The high flows have periodically over topped a part of the downstream bank where channel plugs had been placed to keep the bank intact. It will require lower flows to replace the plugs and protect the affected bank.
Domeier said the river is reconnected to its natural flood plain below the former Marsh Lake dam, and that is positive from a fisheries standpoint. He said he’s confident the river will stay within its historic channel during normal flow periods, but noted some change is inevitable. The original river channel was carved before the dam at the bottom of Lac qui Parle was installed, and consequently there was a greater slope from Marsh Lake to Lac qui Parle Lake.
Allowing the river to re-establish itself naturally will benefit the flood plain and its habitat, as well as the taxpayer, said Domeier. “Let’s let nature figure it out,” he said. “It will do so slowly. It’s a very stable situation.”
In terms of the ecological benefits to be gained, Col. Jansen said the Marsh Lake project has a very high benefit to cost ratio. He credited the project partners with developing the project with cost benefits in mind. It meant that plans to develop horseshoe-shaped islands in the lake to reduce wind vetch on the open expanse of water and a bridge over the new Pomme de Terre River channel were scratched.
However, abutments remain in place at the lake’s outlet and will serve someday to support small bridges for the recreational trail that connects to Appleton.
The project partners said they are confident the project has provided the tools needed to restore the lake to a healthy state.
Trauba cautioned against expecting dramatic changes overnight, however. “This isn’t going to be a light switch. This is going to be a process over time where we build that health back into that system.”