State of the Lake: A Look at Lake Minnetonka's Threats and Challenges

Herbicides in lakes produce results, but are they safe?

Yes, says Dick Osgood, executive director of the Lake Minnetonka Association.

Herbicides were just one of the topics Osgood weighed in on during a State of Lake Minnetonka address last week. He also explored the threats facing Lake Minnetonka and the effectiveness of responses to those threats.

While Osgood described the state of the lake as good, he noted that one word or number cannot adequately describe the lake’s condition. He gave lake management a “mixed” rating.

“Minnesotans take our lakes for granted,” Osgood said.

He explained that the public examines pollutants with an uncritical eye. The EPA lists 126 priority pollutants. The public deems some pollutants on the list that affect lakes, like salt and pesticides, as acceptable because they serve a purpose, he said. For example, treating roads with salt during the winter season makes for drier roads. Yet, Osgood explained that the watershed impacts of such pollutants are long-term, profound and irreversible.

On the other hand, the five-year Milfoil Demonstration Project has used herbicides to control milfoil and protect native plants at five Lake Minnetonka bays. Although the project has been successful at eliminating milfoil nuisances and doesn’t harm native plants, the project has not been without controversy.

People do not like the idea of putting polluting “stuff” in the lake on purpose, Osgood said. However, he argued that herbicides are scientifically regulated to be safe. The demonstration project has shown success while harvesting programs are effective for only six weeks.

“Herbicide concerns are real,” he said, “but the objective foundation is lacking.”

The perceived risk of herbicides is greater than the actual risk, Osgood argued. He said that policies should be based on scientific outcomes rather than just personal feelings. Rain gardens, Osgood noted, do not reduce phosphorus, and prevent greater action on the underlying causes of pollution.

Osgood also spoke about the aquatic invasive species (AIS) that currently—or may in the future—threaten Lake Minnetonka.

“AIS is the defining issue for our lakes of our time” he said.

Currently, the AIS in Lake Minnetonka include common carp, curly-leaf pondweed, Eurasian water milfoil, largemouth bass virus, flowering rush and . Regarding AIS control and prevention, Osgood said the good news is that there are improvements. The bad news, Osgood said, is the lack of a “big hammer” with which to confront the AIS issue.

“There is no systematic approach to AIS,” Osgood said.

There are multiple pathways of entry into lakes, Osgood explained. He pointed to boats and trailers at public and private lake accesses, tournaments and water gardens as some of the pathways for AIS infestation. He described current prevention strategies as leaky and incomplete. Fines, he said, are pitifully low, partly due to a lack of consensus on the impact of AIS on lakes.

Osgood warned that once AIS enters a lake, there is generally no remedy or control.

Other topics included in Osgood’s address were lake level, fisheries and water quality. Lake level management has been successful. However, low lake levels cannot be managed well and management does not mimic natural lake levels and flows.

While most game fish have consumption advisories, Osgood noted that the overall fishery management in Lake Minnetonka is good.

The water quality of most bays are improving, Osgood said, except for the western shallow bays, which have not improved in statistical terms. Water quality is more than murkiness, Osgood said. Lake clarity improved until a leveling occurred  during the late 1990s and early 2000s.

Osgood’s presentation took place at Gray Freshwater Center. The League of Women Voters-South Tonka presented the event. Co-sponsors included the Freshwater Society, Lake Minnetonka Association, the  and Minnesota Waters.