State of the lake
Flathead Lake, the jewel in the Crown of the Continent region, has an estimated yearly economic value of more than $10 billion. The lake's water quality is still high, but new threats loom on the horizon.
By MIKE RICHESON
Bigfork Eagle
More than 220 people attended the Flathead Lakers' annual conference, which was held at the Flathead Lake Lodge this year. In spite of the stifling heat, the audience packed the room to listen to lectures by Dr. Rich Hauer and Dr. Bonnie Ellis - scientists who have amassed a wealth of research while working at the Flathead Lake Biological Station.
Dr. Bonnie Ellis delivered the "State of the Lake" address during the conference. Her verdict: Water quality is still very high, but nutrient loading - especially nitrogen - is eroding that quality.
The high levels of nitrates entering the lake from a variety of sources. Developments near water bodies, lawn fertilizer, septic systems in shallow groundwater and stormwater runoff are the biggest culprits. Because of the extra nutrient loading in the lake, Dr. Ellis said that out of six benchmarks for determining water quality in the lake, two were off target.
The first missed benchmark deals with the increase in the biomass of periphyton, the green slime that covers rocks underwater. Since 1987 there has been a significant increase in this substance due to nutrient loading and warmer water temperatures. Flathead Lake froze over three times in the 80s but hasn't since. Water temperatures on July 25 in the middle of Big Arm bay reached 76 degrees Fahrenheit.
The second missed benchmark concerns the declining trend of oxygen saturation in Flathead Lake. Dr. Ellis said a pristine body of water should record saturation levels of 90 percent, a level the lake hasn't reached since the mid-70s. Dissolved oxygen at midlake deep is now just 75 percent.
So what's going on?
"It all comes back to nutrients, especially nitrates and phosphorus," Dr. Ellis said.
An upgrade of sewage treatment facilities in Flathead County after a ban on phosphorus has worked extremely well to reduce phosphorus levels, but nitrates continue to rise.
The increased nutrient load stimulates productivity of algae and zooplankton within the lake. Bacteria then feed on extra organic matter, which uses up oxygen. Productivity in 2006 was a bit lower than 2005, but the trend has been an increase in productivity.
Some bodies of water, like Lake Mary Ronan, are naturally more productive, which makes the measurement a case-by-case determination. Flathead Lake is naturally a pristine lake, and increased productivity is a negative indicator.
In spite of the missed benchmarks, the overall message was positive.
"Of all the large freshwater lakes in the world that are situated near a lot of people, the lake is doing pretty well," Dr. Ellis said. "Our saving grace is that 61 percent of the watershed is in national park, wilderness and managed forest lands. We're really diluting our pollution with a lot of very clean water."
More than 30 percent of the total watershed that feeds into Flathead Lake is completely protected. But in the areas that aren't protected, development is occurring at record rates.
"Any time you alter the landscape, you increase the possibility of transporting nitrogen," Dr. Ellis said.
Large parking lots significantly contribute to the problem of stormwater runoff, which is an issue Bigfork is currently addressing with the help of County Commissioner Joe Brenneman.
In 1996, scientists from the biological station performed tests on the stormwater outlets in Bigfork, and the results were not good. Substances such as aluminum, iron and zinc all surpassed Environmental Protection Agency requirements. Outlets in Kalispell and Whitefish were even worse. Elements in those areas included dangerous carcinogens.
A possible solution in Bigfork includes treating the stormwater runoff before it pours into the bay.
"We know that as more and more people build, the water quality becomes a huge issue," Dan Barz, Flathead Lakers president, said. "It would be neat to ring the lake with a system that would pump everything into treatment plants."
Barz also said that his organization supports the improvement of Bigfork's stormwater runoff system.
The Flathead Lakers will celebrate 50 years next year. The group is one of the oldest in the United States that has been involved with the preservation of water quality.