Removing aquatic plants discussed
By Angie Landsverk
The city of Waupaca is examining how to manage aquatic plants in Cary Millpond.
It was a topic earlier this month during the annual meeting of the city’s Inland Lakes Protection and Rehabilitation District.
Ted Johnson, a lake biologist in the Wisconsin Department of Natural Resources’ Oshkosh office, was invited to the meeting to speak about aquatic plant management related to the millpond, by Churchill Street.
Johnson’s recommendation to the city depends on the city’s goals.
“That’s our first step, I’m assuming,” Mayor Brian Smith said.
Johnson needs to know if the city wants to pursue a short-term or a long-term plan for the millpond, which has been in the city for more than 100 years.
“When you put a dam on a stream or river, you’re making a sediment trap,” he said.
Johnson said those systems are typically good for about 50 years, before they start to fill in and some type of management is needed.
The options for managing aquatic plants include manual removal of plants, herbicides, harvesting, dredging, partial drawdowns and whole lake drawdowns.
Manual removal of plants is labor intensive and allowed without permits for a 30-foot width around a dock, he said.
A permit from the DNR is required to apply herbicides.
Often used for controlling exotic plants and for navigation channels, that options is expensive and provides short-term relief, Johnson said.
It may impact aquatic insects and plants not being targeted.
Johnson said harvesting is expensive and also requires a DNR permit.
Dredging is another viable tool, he said. It, too, is expensive.
He said drawdowns decrease plant density, while improving lake depths, fish spawning and the overall health and diversity in the water.
There is a loss of recreation opportunities during a drawdown, as well as aesthetic issues.
Johnson said there is a short-term loss of fish populations during a drawdown.
A drawdown can also send sediment downstream, he said.
Johnson said if the city wants to increase the depth of the water, the best time to do a drawdown is in the summer.
He also said a drawdown of Lake Weyauwega is being discussed again.
A drawdown of Lake Weyauwega and the Cary Millpond could occur simultaneously. All the sediment would then run through, Johnson said.
The Crystal River runs through Cary Millpond, and he said Cary Millpond is an effective sediment control for the river.
In addition to learning Waupaca’s goals for managing aquatic plants in the millpond, Johnson would also need more information about the millpond.
“We will need to collect more information, a baseline of what is there now. The city would likely have to hire a consultant for some or all of this work,” he said.
Johnson said it is too late to do anything this winter, but the timing is right to seek funding for next year.
The city could seek grants, use some of the district’s cash balance or tax for costs related to management of the aquatic plants in the millpond.
The mayor said the city has never used city tax dollars for its inland lakes.
Johnson said there are grants for lake planning, including one with a deadline of Dec. 10.
Parks and Recreation Director Aaron Jenson will submit the grant application.
“I’d like to continue with the idea of setting some goal for the Cary Millpond,” Smith said.