Cedar Lake, near New Prague, gets C’s, D’s and even F’s for water quality. Scott County’s top environmental manager has studied 200 lakes and believes he has never seen one as badly infested with one particularly damaging invasive weed.

Oh, and one more thing. It’s the lake in Cedar Lake Farm Regional Park, one of the major new installations in the south metro of the past decade.

The good news: Its status today as the centerpiece of a park has pushed a body of water that’s graded D overall higher on the list of priorities for environmental cleanup.

The bad news: Don’t expect results for many years to come.

“It’ll be 10 to 20 years for many lakes, and Cedar Lake is probably the most difficult of all, because it’s so shallow,” said Paul Nelson, natural resources program manager for Scott County. “It’s probably better classed as a reservoir than a lake.

“Historically, it’s been more like a wetland,” until the state injected more liquid.

What to do

County commissioners peppered Nelson with questions this spring after eyeing a status report classing a lake at the heart of one of their proudest initiatives as badly impaired. What can be done, what is being done, when can results be achieved?

Scientists say that there’s lots more money being deployed than before, but that you’re dealing with severe issues remaining from decades of buildup, with really drastic, faster solutions being ruled out for reasons of public alarm at the side effects.

“Isn’t the ultimate solution to drain it and start over?” asked Commissioner Joe Wagner.

“That’s a very good question,” Nelson said. “We’ve looked at that. But there’s much concern among [the slightly more than 300] shoreline owners. They are concerned about how quickly it would fill up afterward. It could take several years. So we dismissed that because of public concern.”

But the status quo is tough as well, said Melissa Bokman, senior water resources planner.

“It can affect the ability to swim in it. Last year, we had pretty bad blue-green algae bloom, which is a bacteria that looks like algae. When it decomposes it smells like cow manure. We were getting calls saying some farm was affecting the lake. We went out and it was the decomposing algae.”

Carp contest

One new attempt at a solution: to lure sportspeople into a bowfishing contest annually, hoping that thousands of dollars in prizes for the greatest number of carp yanked out of the lake will help.

“The common carp is a nonnative invasive aquatic species that severely impacts water quality in shallow lakes and wetlands,” a flier reads. “Their feeding habits disrupt shallow-rooted plants, muddying the water and releasing phosphorus from lake sediment...”

The first contest, in 2013, was a bit of a dud: Severe weather blew through, and only the bravest souls kept at it.

Another try in May had to be postponed for weather reasons, and then last weekend’s makeup date was hit again by rain, said Brad Eller, a lakes district board member.

“We counted just over 50 fish,” he said Monday, “better than last year’s 40-plus. We actually think we get a lot of biomass out when teams go out and practice ahead of time as well. One team shared with me, ‘we had a 500-pound night because conditions were just right.’ It all helps.”

Officials say the lake’s new stature as a public amenity has helped win funding for attempts to clean it up.

“In the last couple of years we’ve put $100,000 into it, including 2,000 feet of shore land restoration,” Bokman said. And those hundreds of lakeside property owners have stepped up as well.

“In 2007 we hired a firm to sample, and 98 percent of the lake was plagued with curly leaf pond weed, which is a phosphorus source when it dies off around July 4,” she said. “We had meetings around the lake and they all agreed to increase their levy, which they pay beyond property taxes, a special levy for lake improvement, up from a total of $5,000 a year to $40,000, which is matching local, state and federal funds we’re obtaining.”

An expert this fall will do a carp density survey, electrocuting the fish and pulling them out.

Common problem

Water quality is a problem common to lots of lakes, including other major recreational and park-linked lakes in Scott County, such as Cleary, Prior and Spring Lake, which carry official warnings pertaining to either swimming, or eating fish with mercury in their tissue, or both. The state has a website outlining those issues at dnr.state.mn.us/lakefind.

How about other fish that could help eat carp? asked Commissioner Tom Wolf.

“There is data that crappies can prey on young carp and their eggs,” Nelson said. “The population we see are old, large fish, so we will see what ages are there; crappies may be keeping them under control.”

Decades of farming nearby and lawn fertilizer from lake owners are hard things to reverse, experts warn. The county is treating for pond weed, which could be helping, but an official report says there’s been “no change in water quality in Cedar Lake since 2006,” based on 2012 data. Results for 2013 won’t be available until late this year.

County Commissioner Jon Ulrich asked about bounties for carp as a way of spurring folks out onto the water to grab some.

“My concern is,” Nelson said, “are you sure they came from Cedar Lake? If carp are a big issue, a bigger longer-term solution is to put up fish barriers preventing them from spawning and so bringing numbers down by attrition.”