Flathead Lake clarity sign of good health

Visible water clarity is key to determining the health of a water body and this fall Flathead Lake viewers should be able to see up to 17 meters below the surface.

With the last big green algal bloom on the lake in 2008 and the levels of nutrients in the lake about the same as they were last year, the lake’s water quality remains high according to Jack Stanford, director of the University of Montana’s Flathead Lake Biological Station.

“Water quality in Flathead Lake remains really high because we’re doing a really good job of controlling the nutrient loading from the Flathead Valley,” Stanford said. “This lake is on the threshold, if you add nutrients to the lake, it will get green and that means the quality is less.”

Nutrients like nitrogen and phosphates from pavement run-off, fertilizing close to water sources, and sewage treatment plants help feed the algae that has spread across parts of the lake in the past.

While updating the Flathead Lakers on the state of the lake at last Thursday’s annual Flathead Lakers meeting, Stanford said the lake’s water quality is dependant on more than just what goes into the lake.

Stanford said it’s also dependent on what is being taken out of the lake because everything in the lake ecosystem has the potential to affect everything else.

Before mysis shrimp were introduced to the lake in 1977, the level of algae production in the lake was pretty low. But since then, Stanford said production of algae increased 30 percent and oscillated above and below that mark every year since.

When mysis shrimp numbers are lower than usual, the algae numbers drop and vice versa.

The shrimp are what Stanford calls a “strong interactor.” Simply put, they affect the fish and they affect the phytoplankton, which in turn affect everything else.

But Stanford also said “it’s not that simple.”

To truly understand how everything interacts and how doing something like gill-netting lake trout affects the lake, Stanford said he needs to build a full scale computer model.

This would take a couple of years and approximately $1 million in funding.

The Flathead Biological Station already has a significant amount of data they could input into a model because they’ve gathered data for the last four decades. Plus, they are gathering more data now than they did before because last year they put two data monitoring buoys in the lake.

The buoys gather data below the surface of the lake every 25 centimeters six times a day at two different locations — one west of Yellow Bay and one west of Woods Bay.

“This is a major step forward in data monitoring,” Stanford said. “The data set is good and is repeating itself all the way to the ocean.”

Because Flathead Lake and the watershed that feeds it from Glacier National Park and the Bob Marshall Wilderness are the headwaters of the continent, everything that affects Flathead Lake, will affect all the water bodies it feeds into.

So far, the data set shows Flathead Lake is healthier than most water bodies. The biggest reason Stanford gives for this is that the majority of the water that feeds into the lake is protected by wilderness areas.

“We’re in good shape on the pollution side,” Stanford said. “But that could be reversed if we get invasive species in here.”