DNR plan to save algae-plagued lake sparks optimism, opposition

Evan Trompeter wades through algae-filled water in Little Rock Lake.
Eleven-year-old Evan Trompeter wades through algae-filled water in Little Rock Lake near Rice, Minn., on June 22, 2018. Little Rock Lake is among the state's worst when it comes to water quality.
Paul Middlestaedt for MPR News

Six years ago, Aaron Trompeter jumped at what he thought was a great deal on lakeshore property.

He bought his house on Little Rock Lake in early June. But by late summer, entire sections of the lake were coated with bright green algae.

"I don't swim off my dock," Trompeter said during a boat ride last week. "I'll go into the main lake and I'll swim this early in the year. But not in August. In August, it's stinky."

This shallow reservoir of the Mississippi River just north of St. Cloud was once a popular fishing and recreation destination. Today, it's a lot quieter.

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Aaron Trompeter drives his boat on Little Rock Lake.
Aaron Trompeter drives his boat on Little Rock Lake near Rice, Minn. Trompeter owns a house with shoreline property on the lake.
Paul Middlestaedt for MPR News

Trompeter said Little Rock Lake "should be St. Cloud's Minnetonka," but the poor water quality keeps people away.

For decades, the lake was overloaded with phosphorus and nitrogen from a large watershed that drains a lot of farmland. Those nutrients have fueled the growth of algae "so thick that you actually could hear it on the bottom of an aluminum boat passing over it," said Eric Altena, the Minnesota Department of Natural Resources' fisheries manager in Little Falls.

The result: Little Rock Lake has almost no natural plant growth. Plants are an important element of a lake's health — and they keep the shoreline from eroding, Altena said. He said Little Rock Lake is among the state's worst, when it comes to water quality.

For years, residents and experts have debated ways to reduce nutrients and improve the clarity of Little Rock Lake. Most efforts have focused on working with farmers to reduce fertilizer runoff and fixing failing septic systems.

Algae swirls on Little Rock Lake near Rice, Minn.
Algae swirls on Little Rock Lake. Decades of phosphorous and nitrogen washing into the lake from local farm land has fueled the growth of algae.
Paul Middlestaedt for MPR News

Now, they're ready to try a more dramatic approach.

On Aug. 1, the Department of Natural Resources plans to drop the lake level by 3 feet over three days by opening the gates of the Sartell dam downstream on the Mississippi River. The drawdown is expected to expose hundreds of feet of mud flats in the shallower parts of the lake.

If all goes as planned, plants will quickly start to grow in the rich sediment of the lake bottom, using up the excess phosphorus and nitrogen nutrients. Volunteers, including a troop of Boy Scouts, will help by planting native plants in the mud beds.

After six weeks, the DNR will raise the water back to its typical levels. And by next summer, Altena expects to see significant improvement in Little Rock Lake's water quality. He estimates the lake's transparency should increase at least 50 percent.

"Considering that water clarity's usually less than a foot, we'll be doing pretty good," he said.

A boat's wake crests across Little Rock Lake near Rice, Minn.
A boat's wake crests across Little Rock Lake near Rice, Minn. Boaters and swimmers of the Benton County lake are finding algae lurking just below the water, stifling recreation.
Paul Middlestaedt for MPR News

Lake drawdowns aren't a new concept in Minnesota. They have been tried since the early 1970s on several other lakes, including Pelican in Wright County and Swan in Nicollet County.

Most drawdowns have targeted shallow lakes with the goal of eliminating carp or improving waterfowl habitat, said Nicole Hansel-Welch, the DNR's shallow lakes program supervisor.

"We don't purport that this is a magic bullet," she said. "It's one of the tools in the toolbox."

Lake drawdowns have gotten a financial boost from the Legacy amendment — the constitutional amendment Minnesota voters approved in 2008 that dedicates sales tax money to the outdoors, clean water and the arts.

The Little Rock Lake drawdown received a Legacy grant of $198,000, which will pay the company that owns the Sartell dam for lost electricity production. Community donations and the Little Rock Lake Association will cover the remainder of the $235,000 cost.

A great blue heron flies across Little Rock Lake.
A great blue heron flies across Little Rock Lake.
Paul Middlestaedt for MPR News

Kellie Gallagher, lake association president, hopes the drawdown will bring back the Little Rock Lake of her childhood, when she spent time at her grandparents' cabin.

"I remember jumping off the dock in August and it was clear, and I have pictures back in the '70s where it almost looks blue," Gallagher said. "I want that back. I think everybody wants that back."

Lake owners overwhelmingly support the drawdown, Gallagher said. She said the algae growth has made it difficult to use the lake.

In 2007, a particularly bad outbreak of blue-green algae posed a health threat and forced some residents to move out temporarily because of the strong odor.

Thick algae is seen through glass in Little Rock Lake.
Thick algae is seen through glass in Little Rock Lake.
Paul Middlestaedt for MPR News

"From the Fourth of July on, it's pretty hard to find a spot to actually go tube or waterski or whatever you want to do," Gallagher said.

But not everyone is enthused about the project. Residents who live along the Mississippi River downstream from Little Rock Lake aren't happy about missing out on six prime weeks of boating. When the lake level goes down, they'll see water levels on the river go down, too.

Bill Davison said river residents felt shut out of the drawdown decision. He would have preferred a different option, such as erecting a temporary coffer dam and pumping water out of the lake, keeping the river level the same.

"There were better long-term solutions," Davison said.

Mike Nies, who's lived on the river for 21 years, is skeptical the drawdown will make a lasting difference.

Lily pads act as a natural filter for lake water.
Lily pads float in Little Rock Lake. Aquatic plants act as a natural filtration system for lakes, and Little Rock Lake has almost no natural plant growth.
Paul Middlestaedt for MPR News

"It's going to absorb the stuff that's deposited there," Nies said. "But it's not going to do anything for the continuing runoff, the nitrates."

Proponents of the drawdown say farmers in the watershed have made significant strides in curbing pollution.

Since a lake cleanup plan was completed in 2012, the amount of phosphorus entering the lake has been reduced by 2,500 pounds a year, which equates to almost 1 million pounds of algae, Altena said.

After residents had a chance to attend several public meetings and get more information about the drawdown, some of the early opposition has died down, Altena said.

"There's a few that still don't want it," he said. "But they realize that it's going to happen, and they're actually hopeful it works."

A private dock sits in Little Rock Lake near Rice, Minn.
A private dock sits in Little Rock Lake near Rice, Minn.
Paul Middlestaedt for MPR News

Trompeter said Little Rock Lake's water quality should concern everyone, not just those who live on it.

"When I have to worry about my dog getting killed by the lake that is upstream from these towns that pull the drinking water from the Mississippi, this isn't my problem," he said. "It's the people's problem in Sartell, it's the people's problem in St. Cloud, it's the people's problem in Clearwater, it's the people's problem in St. Louis. It's our fresh water."