Portage Lake management plan pays dividends

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ONEKAMA – “Just because we build beautiful houses on the lake and want to recreate on the lake doesn’t mean it’s not a living organism that we need to protect,” said Bre Grabill, environmental scientist at PLM Lake & Land Management Corp.

Grabill made a presentation at a special Onekama Township meeting on May 25 to provide an update on what is being done to ensure Portage Lake is healthy.

Eurasian watermilfoil forms thick mats in shallow areas of a lake and can block sunlight, killing native aquatic plants that fish and other underwater species depend on for food and shelter.


The original Eurasian Watermilfoil infestation in Portage Lake resulted in 40% Eurasian Watermilfoil coverage, according to a 2009 survey.

“It’s extremely high,” Grabill said. “A level of 12 is considered very, very high. If you’re around 40, that’s extremely high.”

Grabill said 161 acres of Lake Portage were treated for Eurasian watermilfoil in 2009, but after a decade of management the number dropped to 49.5 acres in 2018.

• Do not rake leaves in the lake. Rotting leaves produce more slime.

• Do not feed ducks and geese.

• Remove dog, goose and duck droppings from lawns, docks, etc. Don’t just sweep in the lake. Excess feces will increase nutrients.

• Use a phosphorus-free fertilizer.

• Periodically puncture the lawn, seed and mulch exposed soil to prevent erosion.

• Remove aquatic plants, leaves, branches and other debris that wash up along the shoreline of the lake so that there is less decay in or near the lake.

• Use silt fences when building a new home or doing any yard work that would cause erosion.

• Keep all burnt piles and debris piles away from the lake. Ash is a concentrate of nutrients.

• Encourage the use of stone, brick and similar porous materials when constructing a landscape to minimize urban water harvesting.

• Create a natural buffer zone near the water’s edge.


“In a lake the size of Lake Portage, watermilfoil will grow,” she said. “We’re going to have Eurasian watermilfoil, but what we’re doing is investigating that watermilfoil and determining when it’s appropriate to manage it.”

Each year, $24 million is spent to control Michigan’s aquatic plants.

In 2021, less than 2.5% of Portage Lake required treatment of any kind, Grabill said.

Grabill said the Portage Lake treatment program uses the newest form of treatment available in the aquatic environment, one such product being ProcellaCOR, a reduced risk herbicide from the US Environmental Protection Agency.

“It’s really cutting-edge technology to be able to selectively kill the watermilfoil, but to be able to induce the plant to respond so that we don’t have herbicide resistance,” she said.

Herbicides such as procellaCOR can be used safely in the lake, Grabill said.

“Herbicides are designed to attack a plant’s chlorophyll, which is the green part that makes it grow,” she said. “And only plants have chlorophyll. That’s why they use herbicides to attack those plants and why they can be used in our water bodies.”

In addition to monitoring non-native plants in Portage Lake, Grabill said algae levels also need to be monitored.

“It’s very important that we track this, because as a lake ages, you’re going to see more and more productivity,” she said. “With more productivity, you will see more algae. This is an important element in determining the health of a lake based on the amount of algae present.”

Star stonewort is a macroalga that was identified in Portage Lake in 2020. Eight acres of Portage Lake were treated for star stonewort in 2020 and 4.5 acres were treated in 2021.

Grabill said phosphorus levels are tracked because excess phosphorus can lead to increased algae growth. She said that less than 10 micrograms per liter is ideal, more than 10 is considered high and 30 micrograms per liter is a level “that you really need to be concerned about”.

Portage Lake saw levels as high as 70 micrograms per liter in 2012, but levels have been consistently below 10 in recent years.

“In 2012, 13 and 14, you had very high levels of phosphorus in the water body. These levels are high enough to show that we have a real concern,” Grabill said. “However, if you look at the most recent history – except for a peak in 2017 – from 2015, 16, at present the phosphorus readings in the lake are considered very low, so c is fantastic.

“…It’s important to track this so we can try to determine if there are any changes happening in the body of water.”

PLM conducted a total of seven surveys on Portage Lake in 2021.

“Portage Lake has one of the most advanced and rigorous water quality testing programs I know of in the state of Michigan,” Grabill said.

Despite extensive monitoring efforts, Grabill said it’s important for area residents to keep their eyes peeled for signs of trouble in the lake.

“No matter what survey we do, or the committee has done, the residents of the area are the best surveyors I have found,” she said. “…You know the body of water, you know the beach, you know the lake, so you’re probably going to find something faster by being there every day. So if you notice something is different … Say something.

“It is very important that we all act as citizen scientists to help protect the watershed together.”

There were fewer than 15 submerged native plant species in Portage Lake when the lake management program began. The number increased to 20 in 2021.

The lake management program has an annual budget of $83,600. In 2021, only $48,500 had to be spent.

Onekama Township Supervisor David Meister said the township is not saving excess funds and will eventually stop collecting money from the Special Assessment District – a designated area where the majority of landlords agree to authorize a government agency to levy a property tax in exchange for a specific service — in order to deplete the balance.

“At the end of this cycle, we want to end up with $0 in the bank account people have paid into. The township is not just raising $83,600 and pocketing $30,000,” he said. “We’ll balance all of that out at the end of the cycle. There may be a year or two where we don’t need to raise any money, and we’ll spend the money that’s left in the balance.”


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