HAYDEN LAKE - Unfortunately for landowners and lovers of Hayden Lake, it has no outlet streams. Pollutants concentrate as water evaporates.
The primary pollutant of concern to many is phosphorus, and high levels of it yield algae blooms that can be toxic. It also fertilizes invasive aquatic plants like Eurasian milfoil.
In 2011, Kootenai Environmental Alliance began piloting a technology called "floating treatment wetlands," launching three on the lake in areas like McLeans Bay. This summer, eight more are being launched at four other bays, and that work started Friday at Sportsman Park.
The floating wetland mats create a concentrated wetland effect.
"Every 1 square foot of surface area mimics 200 square feet of natural wetland," said Adrienne Cronebaugh, executive director of KEA. "It creates surface area for biofilm to grow."
The biofilm - green slimy looking stuff often seen on river rocks - digests nutrients in the water.
A buoyant matrix mat - made from recycled plastic bottles - is loaded with native wetland vegetation on top. The plants grow into the mats like they are soil and the roots reach into the water below, gobbling up nutrients.
This summer, KEA is working with the Hayden Area Regional Sewer Board, which is chipping in $23,000 for the wetlands and the expensive research into their effectiveness.
The money was set aside after HARBS had a re-use water spill in 2004 and didn't report it in time to the Idaho Department of Environmental Quality.
The DEQ and University of Idaho are helping with the launch and will study the effectiveness of the wetlands.
"HARBS was formed to protect the lake," said HARBS system administrator Ken Windram. Founders were concerned about septic tank drain fields polluting the lake.
"What better way to invest that money than into more research to help to clean up the lake?" Windram said.
Cronebaugh said the money makes expensive testing possible, which is important to show the effectiveness of the wetlands.
"That's really what we're trying to see: 'Are these a cost-effective way of attacking this problem?'" she said.
Hayden Lake will be a test case. Other lakes in North Idaho and Eastern Washington are degrading in the same way.
Marie Pengilly, UI's outreach specialist for the Community Water Resource Center in Coeur d'Alene, said study of the wetlands' effectiveness has been very limited.
"Mostly it's been on wastewater treatment systems," Pengilly said. "In those situations it's been very effective."
She said they will know exactly how much phosphorus is on each wetland when it's launched. The wetlands will all be collected at the end of the summer and the phosphorus will be weighed again to determine how much has been accumulated.
Kristin Larson, a watershed coordinator for DEQ in Coeur d'Alene, said the agency is anxious to see the data.
DEQ will also measure water quality from different distances and depths from the wetlands to determine the "zone of influence."
"We anticipate some sort of cone," Larson said. "We'll just see how far that goes out."
Todd Walker, Hayden Lake Watershed Improvement District lake manager, said he sees the wetlands being most useful on the southern shore where a lot of nutrients are washing into the lake from hills and development. He'd like to see wetlands anchored near culverts there.
Much of the shallower northern end of the lake near Sportsman Park covers what used to be a pasture for cows, so the nutrient loads are expected to continue there.
"Every lake is dying," said Walker, who has been living next to the lake for three decades. "We just want this one to go slowly."