DNR: swimming ‘not recommended’ at Lake Darling

BRIGHTON — The Iowa DNR issued a “swimming not recommended” advisory to guests at Lake Darling after water testing revealed dangerous levels of E. coli at the state park earlier this month.

Iowa Environmental Council Water Program Director Ingrid Gronstal said the bacteria correlated strongly with several other disease risks.

“E. coli, very importantly, is a very good indicator of other pathogens that could be present,” she said. “So if E. coli is present in these high amounts, it’s also possible other pathogens could be present as well, and that’s the reason why they put out the advisory.”

Gronstal said the hazards signaled by swimming advisories were dangerous to humans and animals.

“Microcystin (a toxin associated with excess nutrients) presents a clear causation between pets and livestock being exposed and dying within a few hours,” she said. “It’s a clear and severe link.”

The bacteria — and hazards it correlates with — typically come from manure runoff according to Gronstal, but the state’s routine testing methods don’t have the data to confirm that with certainty.

“It’s a snapshot in time only looking at specific beaches, the program by the DNR isn’t designed to address the sources,” she said. “It’s a very different type of remediation if the E. coli is coming from geese present on a beach versus hog farms in the watershed … while there’s a really good culture of conservation practices in Washington County, it also has the highest (amount) of hog production in the state, so I think that that’s very likely contributing to the impairments in Lake Darling.”

Gronstal said the advisory against swimming was the highest level of enforcement action the DNR would take.

“The DNR never closes beaches, they only issue advisories,” she said. “In all of our conversations with DNR in the last several years, they’re fairly adamant that they don’t close beaches. So if there’s an advisory, that means it’s a pretty serious situation … there’s not a more serious scenario.”

While the park recently returned to an “OK for swimming” status, the warning continued a yearslong trend of poor water quality. The DNR has issued a “swimming not recommended” advisory for the state park at least once every summer since 2020. While the water fell below EPA standards in 2019, it still met the state DNR’s criteria for safe swimming that year.

Gronstal said the continued advisories were a major concern, albeit not an uncommon one for many of Iowa’s water bodies.

“It’s not normal, but it has been normalized,” she said. “Lake Darling is not alone, but that doesn’t mean it’s OK, that doesn’t mean it should be normal. This is a problem that’s happening across the state, and largely because of nutrient pollution.”

Park Manager Nick Young said water improvements were on the radar, but often out of reach at a practical level.

“We don’t do anything specifically day to day to improve the water quality, that’s one of those things that’s kind of a grand project,” he said. “Obviously it’s one of those things that you’re going to have to eventually do more work to restore ... my perspective, as a park manager, I would like to have better water quality, but I know that’s very, very difficult to ask.”

A series of projects at Lake Darling totaling $12 million ended in 2014. About half of that was spent on conservation-oriented concerns like sediment reduction according to DNR Lake Restoration Program Coordinator George Antoniou, who said the trend of hazardous waters didn’t discount the restoration efforts.

“(I) would not necessarily say that that means some of the conservation practices are not working,” he said. “A lot of those that were put on the landscape as part of the more significant effort there, a lot of those (are) still working the way they should.”

In fact, Antoniou said those practices had held up well since their implementation.

“We had about an 80% adoption rate if I remember correctly with land owners in that watershed, and over 160 conservation practices,” he said. “Anything from grass waterways to terraces to sediment ponds. A lot of those did go a long ways in terms of slowing water down and keeping water on the landscape longer and decreasing sediment delivery.”

One explanation for the issues since 2020 is natural change to the terrain, something Antoniou said restoration planning couldn’t account for.

“There’s changes that happen on the landscape over time,” he said. “There may be areas now that need to be addressed that weren’t addressed back in 2010-2014.”

Antoniou also said E. coli tests might misrepresent the lake’s true pollutant situation.

“What we see with E. coli bacteria is it is a bit of a tricky story,” he said. “A lot of times the main part of the lake doesn’t have high bacteria readings. A lot of times it’s beach-specific, or that beach part of the water that they do beach monitoring at … bacteria really like those warm sand conditions and can flourish in that kind of environment, so sometimes it’s not just a watershed story. We may not be dealing with in-lake dynamics that indicate large scale issues.”

Still, he said it was worth keeping an eye on.

“We probably should always continue to be vigilant and look at opportunities up on the landscape as well,” Antoniou said. “We could potentially revisit that watershed assessment process and look for opportunities … we could look at that beach area and see if there’s any ideas there for how to improve drainage or conditions.”

While E. coli test results are still a concern, Antoniou said other indicators of water quality in the park gave reason to be optimistic.

“We track water clarity as a measure … which would support that either from a sedimentation or nutrient perspective that the lake is showing positive signs,” he said. “That metric has remained somewhat stable, with bigger improvements post-restoration. Maybe tracking a little bit now with pre-restoration levels, but still showing an improvement.”

Another area of good news is plant life around the lake, which Antoniou said demonstrated an improved biosphere.

“We have some areas of the lake now that show vegetation and a more healthy perspective from a habitat standpoint,” he said. “Pre-restoration, there were turbid conditions, we really didn’t see … vegetation established indicative of a healthy habitat.”

Lake Darling was hailed in 2014 as a success story and engineering masterpiece for restoration efforts, as projects drastically improved conditions for the artificial lake constructed in the ‘50s. Despite swimming advisories, Antoniou said the Park still had a positive story to tell.

“Back in the mid-2000s, Lake Darling had lost from originally 302 acres down to 270 acres, it had silted in and had a lot of impacts,” he said. “Raising the water two feet so we could have boatable water, a lot of work with shoreline restoration, public access fishing, and an ADA fishing trail … we have a lot of things at that park and lake that continue to be a terrific resource for the community.”

Comments: Kalen.McCain@southeastiowaunion.com