Imagine your favorite lake growing up. Perhaps a family or friend’s cabin hugged its shoreline; when you’d visit this lake as a kid, the water was fairly clear and the fishing was good.
After not having visited the lake for decades, you decide to return for an idyllic fishing trip.
The lake is not as you remember — the water is a pea-soup green, and your shiny, spinning lures aren’t attracting the attention of many fish through the murky water.
This is an example of a severely impaired lake.
Jerry Spetzman, water resources manager for Chisago County, said the term “impaired” has more facets than people realize.
Sure, it’s used for instances when lakes are that murky, pea-green color, but he explained last week that lake impairment is determined on a scale.
“Basically, you’ve crossed a threshold,” he said. “There’s a water quality standard, and if you don’t meet the standard, you’re impaired. You can have just slight differences in water quality from one (body of water) and the next. One could be impaired and another won’t be.”
He noted the main type of impairment is due to an overabundance of phosphorous in water bodies, a problem caused by people.
“In order for anything to be alive, it has to have phosphorous in it, but when you have excess amounts of phosphorous is when it gets to be problematic in lakes,” he explained. “If you get runoff from farm fields or lawns or whatever, a lot of times it’s greatly more concentrated than what the lakes can handle. Phosphorous is the primary impairment for lakes, and it’s what turns lakes green with algae.”
Spetzman said there are other forms of impairment, such as E. coli bacteria, not having enough oxygen in the water and turbidity — silt getting kicked up into the water, sometimes by large fish, like carp — but phosphorous impairment is far more common than these other types.
He said mitigating phosphorous problems in bodies of water can take decades, but Chisago County is working hard to improve the quality of its waters, and that effort will ramp up again as soon as spring comes and the ice and snow melt.
He explained that every year his department and employees from the Chisago County Soil and Water Conservation District take samples of the major water bodies in the county once a month, and through this process they’ve been able to determine what water bodies are impaired.
With that information, the county has developed a watershed restoration and protection plan.
As part of the plan, the county has done total maximum daily load studies, which determine the acceptable amount of phosphorous that can run into a body of water without adversely affecting it.
The county is also involved in more tangible efforts, such as building rain gardens, which help filter water before it flows into area watersheds and then mostly into the St. Croix River, approaching farmers about putting in filter strips on agricultural fields and fixing faulty septic systems that allow pollutants to leach out into watersheds.
These efforts are funded from grants the county has received from the state and federal levels.
“Between the soil and water office and Chisago County, we’ve gotten a lot — hundreds of thousands of dollars in grants from (the state and federal governments),” Spetzman said. “There are tens of millions of dollars available for these types of projects, and Chisago County has been very successful in being very competitive for these funds.”