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Algae Monitoring in Lake Pend Oreille

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LAKE PEND OREILLE- A plan to reduce nutrient pollution in the shallow shoreline areas of Lake Pend Oreille will be developed over the next year by the Tri-State Water Quality Council.

    The Tri-State Council has been awarded a grant from the Environmental Protection Agency (EPA) to conduct algae monitoring, to develop a TMDL (or Total Maximum Daily Load) for the nutrients nitrogen and phosphorus, and to create an on-the ground management plan for the Lake’s near-shore areas.

    The non-profit Tri-State Council--a diverse partnership of citizens, business, industry, tribes, government and environmental groups--works to improve and protect water quality throughout the Clark Fork-Pend Oreille watershed in Montana, Idaho and Washington.

    Due to increasing amounts of nutrients, Lake Pend Oreille has been listed as impaired since 1994 under the federal Clean Water Act.  The listing process requires the State of Idaho to identify sources of pollution and develop a TMDL for recovery of the Lake’s water quality.  Settlement of a lawsuit between the Idaho Sportsmen’s Coalition and the EPA established a 1999 deadline to develop the Lake’s TMDL, which is now overdue.

   “We see this as a tremendous opportunity for people in the Lake’s communities to work together and develop an effective lake management plan that is locally driven,” said Ruth Watkins, Executive Director of the Tri-State Council.    

   A 1993 water quality study, conducted by the three states and EPA throughout the watershed, identified local sources of nitrogen and phosphorus pollution that are likely affecting algae growth in the Lake’s near-shore areas.  Sources identified include discharges from the Cabinet Gorge Dam, the Cabinet Gorge Fish Hatchery, the Clark Fork Fish Hatchery, and the Kootenai-Ponderay Sewer District.  

   Residential development, both around the Lake’s shoreline and in its tributaries, was also identified as a significant source of nutrients.  Among the Lake’s tributaries, Pack River, Sand Creek and Lighting Creek contribute the largest loads of nitrogen and phosphorus.  Additional sources of Lake nutrients cited in the study include logging, agriculture, grazing, septic systems and stormwater.  Generally, the 1993 study found the highest near-shore algae growth in areas adjacent to shorelines with significant residential development.

    While the study also revealed that 80% of the Lake’s nutrient load originates from the Clark Fork River, it concluded that nutrients from the River have more effect on the deeper, open waters of the Lake than on near-shore areas.

    “For the past eight years the Council has focused on reducing nutrient pollution in the Clark Fork River, thereby protecting the Lake’s open water quality,” said Watkins.  “Those efforts resulted in an agreement by the major dischargers along the River to reduce nutrients by 80%, and a pact between the states of Montana and Idaho to allocate nutrient loading at the states’ border,” she added, continuing, “Now its time to focus our efforts on protecting the Lake’s near-shore areas and preventing further degradation of water quality.”

    Excessive nutrients can cause increased growth of algae and other aquatic weeds, which deplete oxygen in the water, impact fish, and reduce aesthetics and recreational uses.        

For more information contact Ruth Watkins, Tri-State Water Quality Council -208.265.9092

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