NAS to prepare water quality study for Lake Cd'A
The Our Gem Coeur d’Alene Lake Collaborative is a team of committed and passionate professionals working to preserve lake health and protect water quality by promoting community awareness of local water resources through education, outreach and stewardship.
COEUR d’ALENE — The Idaho Department of Environmental Quality, with the co-sponsorship of Kootenai County, has contracted the National Academy of Sciences to analyze available data and information and determine future water quality conditions in Lake Coeur d’Alene. The study is endorsed by the Coeur d’Alene Tribe, and the United States Environmental Protection Agency has communicated potential financial support.
Idaho Gov. Brad Little directed IDEQ to secure an independent report to provide confidence to policymakers, stakeholders and the public on future lake management and resource allocation decisions. The governor recognizes the ecological, economical and cultural value of Lake Coeur d’Alene, and is committed to evidence-based, collaborative management.
Historical mining activities (primarily based in the Silver Valley) deposited an estimated 75 million tons of metals-contaminated sediment, including zinc, cadmium and lead, into Lake Coeur d’Alene and its tributaries. Toxic metals are currently settled on the lakebed but may be released under hypoxic conditions (i.e., a water environment low in dissolved oxygen). Oxygen levels in the lake may be altered by increased nutrient loads related to development and land use changes.
The study will assess the near-term risk of toxic metals release, specifically focusing on the following research objectives:
• Evaluate the current water quality in the lake, lower rivers and lateral lakes, with a focus on observed trends in nutrient loading and metals concentrations.
• Consider how changes in temperature, precipitation and streamflow could affect trends.
• Consider the impacts of current summertime anoxia on the fate of the metals and nutrients.
• Consider whether reduced levels of zinc entering the lake as a result of the upgrade to the Central Treatment Plant and other upstream activities are removing an important control of algal growth.
• Discuss whether metals currently found in lake sediments will be released into the lake if current trends continue; if sufficient data are not available to result in a high level of confidence in its conclusions, the NAS will identify the additional data that are required to achieve an appropriate level of confidence.
• Discuss the relevance of metals released in the lake to human and ecological health.
The NAS convened an initial meeting of project sponsors on Dec. 3, and the study will proceed over the next 18 months. The final report is expected in the summer of 2022.
For more information, contact IDEQ Coeur d’Alene Lake Management Supervisor Jamie Brunner at jamie.brunner@deq.idaho.gov or 208-946-0174.