Henderson talks McGregor Lake at open house
Sara Rother, U.S. Army Corps of Engineers, St. Paul District forester, teaches Corps employees and partner agency representatives how to plant a tree at the McGregor Lake Habitat Rehabilitation and Enhancement Project near Prairie du Chien on April 22. (Photos courtesy of Melanie Peterson)
By Steve Van Kooten
On the evening of April 22, the U.S. Army Corps of Engineers — St. Paul District held an open house for the McGregor Lake restoration project from 5–7 p.m. at the Prairie du Chien Memorial Library.
“We’ve been working near Prairie du Chien for four years now — we first started work in the spring of 2020 — and the goal is just to give people an opportunity to come out and say, ‘How’s it going? What’s going on? Here are some things I like, some things I don’t like.’ It’s a good opportunity to engage the people,” John Henderson, the project’s manager, said.
Henderson, who has degrees in agriculture and engineering, believes it’s important to hear from local residents to understand the area’s history.
“It’s trying to get that data and the historical background,” he said. “I think that’s important. What I’ve learned is you could spend your entire life on one of these pools trying to learn all the fishing holes, and you never could.”
The restoration effort, a project under the Upper Mississippi River Restoration (UMRR) program, impacts miles 633–635, part of the Upper Mississippi’s Pool 10, and is a collaborative effort between the Corps, the U.S. Fish and Wildlife Refuge (USFW), the U.S. Department of Agriculture (USDA) and Iowa and Wisconsin’s Department of Natural Resources, among several other agencies. Henderson expects the first phase of the project to be completed later this year.
The project, which started with a feasibility study completed in 2019, began because the area had demonstrated a degradation in habitat diversity due to prolonged water inundation from flooding, tree species dying off and wind wave fetch erosion, according to Henderson.
It wasn’t a sudden calamity; it was a series of problems that crept slowly into the McGregor Lake area.
Leveling out
In 1989, McGregor Lake had aquatic vegetation on 75 percent of its area, according to the Corps’ website, but that number decreased as erosion caused a “leveling out” of the barrier islands and the lake bottoms.
Leveling out occurs when waves — in this case from heavy traffic on the river’s navigation channel — erode the shoreline. When the sediment is pulled from dry land into the water bed, the islands sink closer to the water line, and the lake loses depth from the added soil.
“Not only were the forests starting to erode, we were losing ground from the top down,” said Henderson. “We were seeing a fill-in of the backwaters too.”
Building up islands with dredged sediment from the backwaters created more raised land area for a wider variety of plant species to thrive.
“We’ve found that if you build these islands, you get some vegetation going on them, you get trees going, they’ll become self-sustaining after a while.”
The dredging has relocated sand and fines from the water bottoms to dry areas and simultaneously dug out deeper depths in the backwater area to improve overwintering fisheries.
Henderson said many areas that were 1–2 feet deep are now 5–6 feet. The increased depths will improve fish propagation and recreational opportunities, particularly ice fishing.
In select areas, the Corps constructed rock walls to mitigate erosion on the islands’ shores.
According to the Corps, the project has improved more than 270 acres of aquatic habitat.
Trees and grass
Excessive flooding between 2020 and 2023 damaged many trees in the McGregor Lake area. Trees like oak and ash are less resistant to water inundation and, as a result, have started to die off.
“That’s the difficult part sometimes: we had to take out those dead trees and those really stressed trees to build what we have now,” said Henderson.
The 2019 feasibility study found 85 percent of the trees in the area were a single species (silver maple), which created the potential for a monoculture.
The Corps planted several native plant species in the newly built high areas, including oak, hickories and hackberry. The Corps had to manually plant seeds for some species because the native seed sources had died off completely.
Willows were planted because they can tolerate longer periods of flooding and their webbed roots help preserve the islands. “The root systems will spread and create a net to lock in those shoreline features.”
Corps biologists also concocted a mix of 15-20 grasses and forbs for the island to combat invasive grasses from covering the area. Reed canary grass, for example, grows early in the season, taking sunlight from tree seedlings.
“We’re starting to see those forest cultures really grow,” said Henderson. “Soon, it’s going to look entirely different here with how much vegetation is going to grow.”
Going forward
After the Corps completes construction of the McGregor Lake habitats, the area will be sprayed to protect the new plants from invasive species.
“We’re trying to figure out how to work with the river and help it at the same time,” said Henderson. “Trying to figure out that sweet spot to help it do its thing while helping it in a way that it needs to go.”
