In the early 1980s, Delavan Lake was a mess. It was full of algae, which fed on nutrient-rich runoff from nearby lawns and fields. Only 2,000 boats hit the lake each year because the only fish thriving in the sludge were carp and bullheads.
"It had lost any resemblance to nature's healthy balance," said Delavan Lake Improvement Association Board member Mary Knipper. "There was no chance of it naturally pulling itself out of the slump."
Delavan Lake Sanitary District Administrator Kevin MacKinnon agreed.
"It was pea soup from Memorial Day to Labor Day," said MacKinnon, who recently was recognized by the Wisconsin Lake Association for the quality and quantity of his work on Delavan Lake.
In 1989, local, state and federal governments, scientists and citizens stepped in and launched a $7 million restoration project.
Knipper and MacKinnon are quick to call the restoration a success. The lake is full of healthy game fish and more than 15,000 boats. The water is crystal clear.
Sometimes.
U.S. Geological Survey research hydrologist Dale Robertson said the restoration yielded mixed results.
Fishing has improved greatly, he said, but water quality is hit or miss.
"The real bad algal blooms have decreased significantly," Robertson said. "But during July and August, it's not terribly different than it used to be."
Dredging will resume soon on a $1 million maintenance project, but to improve the lake's health, even more work is in store, Robertson said.
What happened?
The 1989 restoration project was intended to remove sediment and nutrients from the lake and keep them out by improving wetlands.
The project included:
-- Dredging the wetlands and parts of the lake itself.
-- Lowering the water level 10 feet and killing trash fish.
-- Restocking game fish.
-- Using aluminum sulfate to pull phosphorous out of the water and lock it in the lakebed.
Did it work?
The difference between then and now is startling, said Knipper, who has lived on the lake since 1974.
"We see ice fishing all winter and hordes of boats in the summer," she said "They all talk about what a delight it is fishing on Delavan Lake."
DNR fish biologist Doug Welsch said a spring 2006 survey of Delavan Lake revealed four to five adult walleye and two to three northern pike per acre, along with other game fish.
"Which is excellent," Welsch said. "Overall the fish population is very healthy."
"A" for effort
Lake improvements can be attributed to the hard work of many, Robertson said.
"Right now Delavan is probably putting in more effort than on any lake I've seen in the state," Robertson said. "They're basing their decisions on science. They're trying to do what's best, but they're real high on the learning curve."
Tests show the lake is twice as clear than it was before the 1989 restoration. And harmful nutrient levels are a third of what they were.
Desirable phosphorous levels are about 30 micrograms per liter. In 2005, the lake contained about 60 mpl. That's much better than 150 mpl in 1984, but it's not perfect, Robertson said.
A new dredging project, estimated at just less than $1 million, will keep nutrient levels from worsening, Robertson said. Removing sediment from basins in the Mound Road wetlands and Jackson Creek will help Mother Nature filter water before it gets to the lake.
"That's not going to improve anything in the short term," Robertson said. "It's just going to keep things from going downhill."
To make a long-term difference, nutrients need to be reduced from the entire 40 square mile watershed.
Every urban developer has to be certain new projects limit runoff as much as possible, Robertson said. Farmers need to follow best practices.
And residents need to support dredging projects, avoid phosphorous fertilizers and encourage local businesses to do the same.
Facts
Size: 3.2 square miles
Size of watershed: 40.8 square miles
Deepest spot: 56 feet
Average depth: 21 feet
Type of fish: muskie, northern pike, walleye, large- and small-mouth bass
Annual number of boats: 17,000
Timeline
-- 1969-Delavan Lake Sanitary District created to improve lake water quality.
-- 1989 to 1993-State, federal and local governments undertake a $7 million restoration project on Delavan Lake and its watershed.
-- 1993-Heavy rainfall negates improvements made in nutrient reduction in lake. Over time, nutrient levels decrease by 30 percent.
-- 1997-Aquatic plant management program begins. Town of Delavan bans the use of prosperous fertilizers for non-agricultural use in the Delavan Lake Sanitary District.
-- 2004-Lake defined as "eutrophic"-rich in nutrients as well as plant and algal growth.
-- October 2005-Sho-Deen Construction Co. presents plans for the Jackson Creek residential development.
-- October 2006-Town of Delavan approves funds up to $700,000 for new dredging projects.
-- November 2006-Dredging begins on the channel and wetlands.
-- December 2006-The city of Delavan bans the sale and use of phosphorous fertilizer for non-agricultural purposes.
-- January 2007-The Town of Delavan Plan Commission rejects Sho-Deen's proposal.
-- April 2007-Sho-Deen rescinds proposal.
Quote
"Right now Delavan is probably putting in more effort than on any lake I've seen in the state. They're basing their decisions on science. They're trying to do what's best, but they're real high on the learning curve."
-Dale Robertson, research hydrologist with the United States Geological Survey.
Upcoming event
The Delavan Lake Improvement Association will host its annual "State of the Lake" meeting from 8:30 to 11 a.m. Saturday, May 26, at Community Park, Highway 50 and South Shore Drive, Delavan. Topics will include an update of current projects, an overview of the Delavan Lake watershed and the importance of ecologically friendly agricultural and development practices.
