What's with Lake Calhoun's water quality?
Beach closings at Lake Calhoun this summer have left many wondering what's going on. The closings occurred in early August, leaving swimmers waiting on the shore.
Sara Aplikowski, water resources coordinator for the Minneapolis Park and Recreation Board, said after a beach closing she often gets calls from concerned swimmers, wondering if they're safe.
They are, she said; aggressive monitoring means shutdowns occur well before human health is affected.
Most folks seem to go back in the water. Augustina and Nicolas Borroel swam at the lake's North Beach with daughter Melina, 2. Augustina Borroel said she's been swimming in Lake Calhoun twice and likes it because it's cleaner than other area lakes. "If it looks dirty, we don't get in the water," Borroel said.
Aplikowski said despite the shutdowns, Calhoun's water quality has improved based on city/county monitoring reports.
So what causes the closures? And what's being done to make sure they happen less often - or not at all?
What affects water quality?
Bruce Wilson, a research scientist for the Minnesota Pollution Control Agency (MPCA), said animals are the largest cause of shutdowns, especially with respect to E. coli, the bug responsible for most of Calhoun's closures.
Every warm-blooded animal has E. coli in its stomach.
"You go to the Chain of Lakes; I walk my dog, everybody walks their dogs. You've got a heavy concentration of animals using that area. Even if people pick up after their animals, you've got a lot of fecal materials," Wilson said. "So you get warmer temperatures with bacterial sources, you can have increased concentrations [in the lake]."
Dogs aren't the only culprits; Aplikowski said that goose poop is another significant factor. Animal sources are usually the reason behind E. coli-related shutdowns, which often happen after summertime rains flushes their droppings into the lake. (Nobody mentioned diaperless babies as a prime contaminator.)
Aplikowski stressed that it's a misconception that because of these periodic high levels that the water is unsafe.
"We are being very active and progressive about closing the beaches at EPA guidelines" that limit the number of E. coli colonies per milliliter of water, she said.
Humans aren't blameless. Aplikowski said anything that might go down the storm drain gets flushed into the lakes. Wilson said things like fertilizer and even rotting leaves can produce nitrates and phosphorus that promote algae blooms that harm water quality.
"Phosphorus is one of the big problems for lakes in this area," Aplikowski said.
The Park Board tests and keeps records of each lake's Trophic State Index (TSI), which measures water transparency, algae levels and phosphorus in area lakes.
According to Park Board reports, Twin Cities lakes should maintain a TSI score of 59 or lower. Between 1991 and 2003, Lake Calhoun's TSI fluctuated between 59 and 43; the lower numbers are more recent, indicating improved water quality.
While Minneapolis beaches seem to close more often than those in the 'burbs, Aplikowski noted that many cities don't test the water, so they have no shutdowns to draw attention to poor water quality.
How is the water maintained?
Many different groups have a hand in maintaining Lake Calhoun's water quality and that of other Southwest Lakes. While the Minneapolis Park and Recreation Board is the sole group in charge of monitoring, the state MPCA oversees the process and a Hennepin County group helps and works on water improvement projects.
Aplikowski said her three-employee, two-intern staff does maintenance, including an ecological monitoring, every other week and a twice-weekly public beach monitoring.
She said the ecological monitoring measures phosphorus levels, nutrients and temperatures, using instruments and water samples. The public beach monitoring uses water samples.
While the city is solely responsible for the monitoring, Hennepin County is the taxing agency and assists in lake grading and major projects.
Mike Wyatt, environmental planner for the Hennepin County Minnehaha Creek Watershed District, said his agency helps compile reports on water quality and grades lakes within the watershed district.
The watershed district runs from the western town of St. Bonifacius to the Mississippi River - 181 square miles of water.
Katie James, an environmental health intern with the county's Human Services and Public Health Environmental Unit, tests Lake Calhoun's water with a water-monitoring device and takes samples.
James said that the machine has a data reader and probes on the end that test water pH levels, conductivity and other water measurements. She said it takes readings in a few seconds.
As she waded into Lake Calhoun, she said it currently takes 24 hours get a lab sample test for E. coli, but she's testing with the aforementioned machine in hopes that it could be able to forecast unhealthy bacteria levels by tracking changes in beach sample readings.
While continued monitoring helps track the water's makeup, a major multi-agency, multicity project has greatly improved Lake Calhoun's water quality.
The Minneapolis Chain of Lakes Restoration Project was a $12.5 million effort from 1990 to 2000.
The MPCA's Wilson said all government agencies worked together and set numeric goals for lake water based on total phosphorus levels. He said changes were made to the water system to help achieve the targeted numbers.
From that, Wilson said they designed a plan and added sediment basins, such as one at West 44th Street & Calhoun Parkway. He said Minneapolis city stormwater renovation projects near the lakes have also improved water quality.
As for the results, Wilson said, "This has absolutely nailed it - we got reductions. But keep in mind these are living systems and there's a lot of people around, so there's always things to do - heavy operational maintenance forevermore."
The results are reflected in the TSI improvements from 1991 and in the MCWD's annual report cards, which shows Lake Calhoun going from a B+ in 1998 to a solid A for the past three years (see chart.)
Wilson said, if measures hadn't been taken to fix the lakes, the previous conditions could have resulted in harm to recreational uses, such as swimming, causing algae blooms (green scummy stuff) and toxic algae that can hurt animals - killing dogs, for example.
"It can be very, very expensive - prohibitively expensive - to try to go fix something once it's broken, so protection, protection, protection," he said.
Wilson noted that monitoring water quality is a serious issue. "This is not small potatoes; this is not just a minor thing. This is people's heart and soul and property," he said.
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