Alliance favors lower water levels on Lake Winnebago to reduce algae blooms

APPLETON - The Fox-Wolf Watershed Alliance has floated a proposal to lower the water levels on Lake Winnebago in an effort to improve water quality and curtail algae blooms.

The change would reduce the summer navigation water levels by a tenth of foot (1.2 inches). It also would delay, from June 1 to June 15, the filling of the lake, and it would maintain the summer levels through October, rather than September, to extend the fall boating season.

In addition to Lake Winnebago, the upstream lakes of Butte des Morts, Winneconne and Poygan would be affected.

Korin Doering, Winnebago waterways program coordinator for the Fox-Wolf Watershed Alliance, said the slight change in water levels could yield widespread benefits.

"The reason for the change is to restore aquatic plants and water quality by allowing sunlight to reach the bottom in more of the lake during critical plant growth periods," Doering told USA TODAY NETWORK-Wisconsin.

Aquatic plants produce oxygen, stabilize sediment and compete with algae for nutrients.

"If we reduce the intensity and severity of those blue-green algae blooms, we don't have to worry so much about toxins in the lake while people are swimming and fishing and boating," Doering said.

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The U.S. Army Corps of Engineers will hold a meeting at 6 p.m. Thursday to discuss the strategy and gather feedback from shoreline property owners, boaters, anglers, environmentalists and municipal and utility representatives. The meeting will be held at the agency's Appleton office at 2619 E. Capitol Drive.

"Our aim is to hear as many different comments and hear from as many different stakeholder groups as possible," said Keith Kompoltowicz, chief of watershed hydrology for the Detroit district of the Army Corps of Engineers.

The Corps of Engineers regulates the water levels in the Winnebago lakes by coordinating the gates at the Menasha and Neenah dams. The crest of the Menasha dam is 1.68 feet above the Oshkosh datum, which is a measure of the surface elevation of the water, not the depth of the water.

The 2018 summer water levels were set at 2.9 to 3.1 feet above the Oshkosh datum. The proposed levels would be 2.8 to 3.0 feet above the Oshkosh datum.

The target for the drawdown of the lakes in the winter would be set at 1.2 to 1.7 feet above the Oshkosh datum. Currently, the winter target is 1.2 to 2 feet. The lower level would create more storage for the snowmelt and spring rains, minimizing the potential for flooding.

"If the lakes are too full when the spring surge happens, then we end up getting close to, if not exceeding, flood stage in Lake Winnebago," Doering said. "We want to prevent that."

Doering said turbidity and higher water levels in the summer have contributed to a loss of aquatic plants in the Winnebago lakes. Without competition from plants, blue-green and filamentous algae thrive in the nutrient-rich environment. Unsightly, foul-smelling algae blooms can affect recreation, tourism and water-treatment costs.

Lowering the water levels could restore balance, Doering said.

"This is something that isn't going to happen overnight," she said. "It's not going to happen in one year. It's something that is going to take a few years to see progress, but water-quality improvements take time."

Boaters and property owners have expressed concern that lower water levels, combined with the unpredictability of Mother Nature, could result in too much plant growth.

They remember the drought conditions of 2010, when plant growth flourished and impeded navigation on Lake Winnebago.

"Down here on the south end, you couldn't even get your boat out because the weeds were so thick," said Tom Marcoe of Fond du Lac.

The Fox-Wolf Watershed Alliance recommends a committee be formed to develop strategies for managing plants that grow to nuisance levels.

USA TODAY NETWORK-Wisconsin reporter Sarah Razner contributed to this report.