Report Card Reveals High Grades for Lake Minnetonka Water Quality

Overall water quality in most areas of Lake Minnetonka tests good or better, as measured in data released today by the Minnehaha Creek Watershed District. 

That’s great news for the throngs of fishing boats expected to converge on the lake for this weekend’s season opener.

Of the 26 bays tested, nearly half scored an “A,” with four others given a “B” and six receiving a “C.” Tanager, Jennings and Holsted bays received a grade of “D.”

“Some of the poorer water quality sites used to have sewage treatment sites on them, so that’s why the water quality isn’t as good,” said Kelly Dooley, a lakes water quality technician with the district.

Dooley spoke Monday at the boat launch on Carsons Bay in Deephaven, where water quality received an “A” for the third consecutive year and fifth time since testing there began in 2004. Dooley said bays such as Carsons, Wayzata, Excelsior and others around the eastern side of Lake Minnetonka have some of the best water quality in the region.

“They’ve all been pretty consistent over the last five years,” Dooley said. “Some bays may never get to an ‘A’ just because of how they always were since the beginning, but we can improve them.”

Grades are based on three factors: total phosphorus levels, algae abundance as indicated by chlorophyll-a measurements and Secchi disk readings. Grades remain virtually unchanged or have gone up for most Lake Minnetonka bays since testing on them began, with none experiencing dramatic downgrades.

Because they are able to absorb higher levels of contaminants, bays with deeper water consistently receive higher grades that shallow areas.

Stu Boyd won’t say exactly how long he’s live on the lake, only hinting that it has been a considerable number of years. Boyd was pleased, though not surprised, to hear that the water outside his east window is among the best in Lake Minnetonka.

“Well, it’s a beautiful lake,” he said. “What makes it beautiful is that you have an extraordinary amount of people willing to do their part. Most of us who live on the lake don’t view it as ‘my lake.’ We see it as ‘our lake.’”

Pet waste, lawn clippings, fertilizer or other chemicals that reach Lake Minnetonka represent some of the biggest threats to localized water quality. These and other contaminants typically enter the water via storm drains, going unfiltered into streams and tributaries.

From the Minnehaha Creek Watershed District: 

The Minnehaha Creek Watershed District’s lake grading method was developed in 1989. The grade shows how your lake measures up compared to other area lakes. Grades are an indicator of the perceived condition of the open water. Three water quality parameters are combined to calculate each lake grade . There are, of course, other factors that contribute to lake condition – for example, aquatic plants, fisheries, harmful chemicals, over-use, etc.

Among the factors affecting a lake’s grade is the weather. There was a 12 percent increase in average rainfall in 2010. Above average precipitation can often result in more runoff that can carry pollution to our lakes and streams.

There are measures people can take to help improve their local lake’s grade.They can take advantage of the district's cost share grant programs, which help pay for the installation of rain gardens, pavers and shoreline plantings that prevent runoff from carrying nutrients and pollutants into our streams and lakes.