| Coeur
d'Alene Lake, Idaho's second largest, has undergone several studies
to evaluate water quality and determine the need for remedial actions
to protect the lake against degradation. Studies have focused primarily
on nutrient and metals concentrations. The lake has been the recipient
of trace-element-enriched mining and smelting wastes that were produced
over 100 years by mining and ore-processing activities in the Coeur
d'Alene River drainage basin.
A nutrient loading study
conducted in 1975 classified Coeur d'Alene Lake as mesotrophic,
or moderately productive, and recommended that additional studies
of the sources and magnitudes of nutrients be performed prior to
development of a lake management plan. Nutrients promote growth.
In excess, nutrients in water bodies may accelerate algae growth,
reduce swimming and boating opportunities, create a foul taste or
odor, and kill fish by reducing the amount of dissolved oxygen in
the water and increasing the pH.
Subsequent to the 1975 study, various water quality studies of Coeur d'Alene Lake were conducted by the U.S. Geological Survey (USGS), Idaho Department of Environmental
Quality (DEQ), and the Coeur d'Alene Tribe. A 2002-03 study
revealed that as a whole, Coeur d'Alene Lake exhibits relatively high water quality, while some specific geographical areas of the lake are experiencing specific water quality problems. Based upon a review of the results of that study, it was determined that the best approach to protecting the lake's water quality would be to develop strategies for addressing water quality problems in four different lake zones: nearshore, shallow southern lake, lower rivers, and deep, open water.
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