Structure will allow drawdown, management of Olson Lake to improve waterfowl habitat

RAYMOND -- For migrating waterfowl, Olson Lake in southern Kandiyohi County has become one "big, dirty bathtub.''

The transformation is easy to see from a duck's aerial perspective, according to Josh Kavanagh, a biologist with Ducks Unlimited. He pulled out an aerial photo of the lake revealing that only a few decades ago, as much as 50 percent of the shallow lake was filed with stands of emergent vegetation.

Today, its 140 acres of water are as wide open as an asphalt parking lot, and very turbid as a result. Winds rip across the lake and churn the waters. There is no longer the mosaic of vegetation that used to provide cover and feed to waterfowl.

We know the lake's waters now teem with bullheads and flathead minnows, according to Steven Erickson, with the U.S. Fish and Wildlife Service in Litchfield. He eyes the far shoreline with his binoculars and sees occasional splashes as fish break the surface, suggesting there are carp here as well.

The fish stir up the waters and devour the invertebrates that would keep algae in check. The algae blooms block sunlight needed by underwater plants.

Absent that vegetation, phosphorus remains in the water and continues to feed algae blooms. Kavanagh tested the lake earlier and measured phosphorus at 215 parts per billion, well above the 90 ppb threshold for impaired waters.

Erickson summed up the duck's view on the lake this way: "When the grocery store is empty, you don't drop in.''

We had good reason to drop in at Olson Lake recently.

We came to see progress on a project that will draw down the waters of this lake. Duininck Brothers Construction of Prinsburg has installed a control device and buried a 3,500-foot long, 24-inch diameter plastic pipe from the lake to its outlet into Kandiyohi County Ditch 31.

Over the course of 72 days or more, it will be throwing out the dirty bath water by lowering the lake and exposing the lake bed. The undesirable fish will be eliminated.

Exposed to air and sun, the quicksand-like bottom will firm up and native vegetation will take hold again.

Water will slowly be returned, and in a couple of years Olson Lake could again be attracting the flocks of waterfowl that once made this lake a few miles east of Raymond a popular destination for hunters. It's part of a larger, 400-acre plus wildlife area.

The draw down will recreate what nature used to do on its own, said Kavanagh.

Before we so dramatically altered the landscape, water levels fluctuated naturally in shallow lakes. Low water meant winter kill and conditions that kept flathead minnows, bullheads and carp from damaging the aquatic vegetation and slurping up the invertebrates.

"Like fire on the prairie,'' said Kavanagh of the importance of occasional, low water periods to shallow lakes.

With a control structure in place, the water drawdowns can be accomplished in future years to mimic natural cycles, noted Erickson.

Olson Lake is one of 5,000 shallow lakes of more than 50 acres in Minnesota. The state has a goal of restoring 1,800 of its impaired shallow lakes in the next 50 years, according to Nicole Hansel-Welch, program leader with the Minnesota Department of Natural Resource's shallow lakes effort.

Minnesota has a long way to go to restore its shallow lakes, but is making progress, she said. More people are becoming aware of how important shallow lakes are, and we're beginning to manage more of them.

In the case of Olson Lake, a partnership of the U.S. Fish and Wildlife Service, Ducks Unlimited, the DNR and Hawk Creek Watershed Project is making this project possible. Its total cost is just over $170,000, according to Erickson.

Its value will be known by the numbers of waterfowl and non-game species that will return to the waters as desirable vegetation again takes hold and water quality improves.

Downstream waters will benefit too, noted Darrel Schindler, coordinator with the Hawk Creek Watershed Project. There will be less phosphorus and sediment leaving the lake and eventually flowing into Hawk Creek and the Minnesota River.

Thanks to his work with Ducks Unlimited, Kavanagh has witnessed draw downs take place on other shallow lakes like this one, and knows what is coming. "The response you get is amazing,'' he said.