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One lake at a time

Work crews dig out an area for a large water pump near Cory Lake on the Hamlin Wildlife Management Area near Dawson. The Minnesota Department of Natural Resources and Ducks Unlimited will draw down the lake into the Lac qui Parle River. Submitted photo

DAWSON -- A wall can't be built without placing the first brick. A house does not become a home until the first picture hangs from a wall.

And an initiative to improve the water quality for waterfowl from southwestern Iowa to northwestern Minnesota can't be completed until many of these little lakes can be cleaned up.

One of these 'small steps' is Cory Lake, which is a 147-acre pothole on the Hamlin Lake Wildlife Management Area west of Dawson. At about 4½-feet deep, Cory Lake could be a prime resting spot for waterfowl during their fall migration south.

But as we've seen over the years, the ducks and geese bypass many of our area shallow lakes because of a lack of food, like wild rice in northern Minnesota and aquatic invertebrates in the small ponds. Cory Lake, which is directly connected to the Lac qui Parle River, teems with unwanted carp, bullheads and other roughfish.

"The water quality is very poor likely due to the fish issue," said Curt Vacek of the Minnesota Department of Natural Resources' Wildlife Office near Watson. "It's just in a stagnant state and it has been for a few years. We've been wanting to do something about it."

And do something, they will. As part of the DNR's Duck Recovery Plan and Ducks Unlimited's Living Lakes Initiative, Cory Lake will be drawn down to allow for winterkill and hopefully drained to allow for vegetation to come back after years of being rooted out by fish.

Cory Lake is one of a number of small prairie lakes in the region to begin the process of restoration, including Ash Lake in Grant County and Round Lake near Lake Shetek in Murray County.

With grant money from the recently-established Outdoors Heritage Fund and the North American Wetlands Conservations Act, plans were made to draw down the water level at Cory Lake. But there was a slight problem.

"We wanted to do a gravity drawdown, but we'd still be left with about three feet of water," Vacek said. "You'd still get fish survival in the winter."

To drain a body of water, it has to be drawn to a lower elevation, which wouldn't work at the Hamlin WMA. The water would have to be pumped out.

"We would have to find four feet below the lake that was close, then clean the channel downstream to mitigate the draining from the structure," said Josh Kavanagh, a regional biologist with Ducks Unlimited.

Crews went to work on clearing land for a large water pump station. Getting the job done was made a lot easier because they were working on state-owned land, Kavanagh noted. The pump can move 3,000 gallons of water per minute and the water will be pumped back into the Lac qui Parle River.

The sheet pile structure will work as a barrier to fish and also allow site managers to adjust the water levels in smaller increments. That's important to the adjacent land, which could be affected during large runoff events like the spring melt or huge thunderstorms.

"We will not be pumping during main water flows," Vacek said. "If there is a big rain event or anything like that, we would turn off the pump."

The pump was christened Dec. 3. Kavanagh said clean-up work continues and then an inlet pipe will need to be installed. He estimated the project is at least 90 percent complete.

Plans are to have a total drawdown to destroy the fish and keep the water control structure up in the spring to keep more fish from the river out. After the spring melt, Kavanagh said the lake bed will be pumped dry again.

"Once you do the full draw down, you bring the plants back and stabilize the bottom sediments, and clean the water that flows downstream," he said. "We're trying to monitor those benefits through water sampling. The vegetation takes nutrients, which improves water quality."

When Cory Lake starts drawing waterfowl and the water clarity improves, controlling the water levels shouldn't be a concern year-in and year-out.

"We're expecting to have to pump it dry every seven to ten years, is my guess," Vacek said.

Other projects at the WMA include testing methods of shoreline restoration.

Vacek said they will disc up plots around the lake when the ground dries next spring to help bring up more vegetation.

"With these basins and sediment coming in, we're going to expose the sediment to get at the old seed bank to see if we can stabilize the growth around the lake. We'll do it a little at a time," he said.

Living Lakes

In 2004, Ducks Unlimited launched its plan to improve the water basins from Pool 19 on the Mississippi River in southeastern Iowa to the wild rice lakes in northern Minnesota. Called the Living Lakes Initiative, the plan is to protect and manage shallow lakes to provide quality wetlands for waterfowl habitat.

"The program is growing. We're taking on more and more projects each year," said Kavanagh. "We're seeing on the lakes we are managing, clear water with vegetation and aquatic invertebrates for these migrating birds. We're doing a good job of building and have great partners in the DNR and others. The list continues to grow."

The DNR's Duck Recovery Plan was approved in April 2006 with the goal to "Recover historical breeding and migrating populations of ducks in Minnesota for their ecological, recreational, and economic importance to the citizens of the state."

Added benefits

Like most conservation-oriented projects, the Cory Lake water pump will improve not just the waterfowl value of the lake, but also the water quality.

"Our focus is not on just this wetland. We want to improve the entire watershed," Vacek said of the 3,000-acre area that runs into Cory Lake. "This is how we're improving water quality in the basin."

To see the benefits of a drawn down lake, look no further than Olson Lake near Raymond. Drained of water to kill fish and allow vegetation to re-establish itself, it could become a treasured spot for ducks and duck hunters alike.

"The (U.S.) Fish and Wildlife Service plan is to bring water levels back to normal," said Kavanagh. "A lot of vegetation has really grown; lots of cattail growth. Next fall, that's definitely going to be worth checking out to see if the birds are there."

Kavanagh also noted discussions are ongoing to start a similar project at the Henjum Lake Waterfowl Production Area west of Henjum Lake near New London. He said surveys are being done on water level management possibilities.