Researchers at the Idaho Department of Environmental Quality are seeing more phosphorous in Lake Coeur d’Alene, and recent state funds could help determine why the trend is happening and how to slow it down.
The department estimated that, on average, more than 180 tons of phosphorous enter the lake each year, a number that shows a definite increase from data collected in the 1990s, said Craig Cooper, limnologist at the department of environmental equality.
More phosphorous levels can lead to lower oxygen in the Coeur d’Alene water basin area, which could then add to the risk of toxic green-algae blooms and metal contamination, Cooper said.
Though they don’t know what caused the uptick, Cooper said he believes changes over time to the landscape – clearing trees, pavement, increased construction – contributed to the recent rise in phosphorous.
Research has shown, among other things, that the volume of phosphorus flowing into the lake has roughly doubled since the 1990s. That’s a troubling development for a lake that has roughly 75 million metric tons of sediment polluted with lead and other heavy metals, the toxic legacy of more than a century of mining in Idaho’s Silver Valley.
“We don’t really understand how much of what is causing the phosphorous to go up,” Cooper said. “We can say in general … that, yes, phosphorous is going up. Yes, humans have influence that we can assess and measure.”
All of which matters because oxygenated water acts like a cap on the metals, keeping them locked in the sediment.
The next step is now in the hands of a Coeur d’Alene Lake Advisory Committee that will choose and fund projects aimed at phosphorus reversal and other water pollution sources. Projects that prove to be timely and have the biggest reduction in phosphorous will be given priority, according to a news release from the Idaho Department of Environmental Quality.
Idaho Gov. Brad Little announced Aug. 20 he directed $2 million for projects that would attempt to reduce the amount of nutrients in the Coeur d’Alene Basin, according to a news release.
Cooper, who will offer advice to the committee, said some solutions could be to fund better storm water management and restore original stream flows, both of which proved to be factors in the amount of nutrients sent into water sources.
Though the committee does not have any researchers from the department of environmental quality, Cooper said it will work with researchers and the community to determine how to prioritize the projects while balancing what residents want.
“The science we’ve done has told the community that nutrients are increasing in the lake, there is a long-term threat that’s taking us in a direction we don’t know,” Cooper said. “We’re driving the wrong way on the road … when you’re going the wrong way, you don’t keep going the wrong way. You stop and turn around.”
The committee’s first meeting focused on the biological and ecological structure of Lake Coeur d’Alene as well as how phosphorous levels will affect the future health of the lake, according to a news release from the department. The committee will have its second meeting on Oct. 20.
The National Academy of Sciences started a review of years of water-quality data from Lake Coeur d’Alene this year.
The information in question has shown a continued deterioration in the lake’s health and spurred calls for more drastic action to protect the North Idaho gem, although some question the validity of the data.
Local journalism is essential.
Give directly to The Spokesman-Review's Northwest Passages community forums series -- which helps to offset the costs of several reporter and editor positions at the newspaper -- by using the easy options below. Gifts processed in this system are not tax deductible, but are predominately used to help meet the local financial requirements needed to receive national matching-grant funds.
Subscribe to the sports newsletter
Get the day’s top sports headlines and breaking news delivered to your inbox by subscribing here.