Clinch and Powell Valley Watershed Ecological Risk Assessment
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A watershed ecological risk assessment of the unique Clinch and Powell river system in southwestern Virginia strongly suggests that (1) coal mining activities and agricultural practices, past and present, are having adverse impacts on stream habitats, resulting in unacceptable losses of valuable and rare native fish and mussels and (2) prompt implementation of practical risk-lowering actions, such as reclaiming abandoned mines, spill prevention, excluding livestock from streams, and establishing riparian vegetation zones, can mitigate these adverse effects in the future.
The free-flowing Clinch and Powell Valley watershed, which drains into Norris Lake in northeastern Tennessee, has historically had one of the richest assemblages of native fish and freshwater mussels in the world. Nearly half of the species historically present are now extinct, threatened, or endangered. The U.S. Environmental Protection Agency's ecological risk assessment framework was used to structure a watershed-scale analysis of associations between land use and in-stream habitat and their effects on fish and mussels.
A pilot study of one of four subwatersheds determined that the fish Index of Biotic Integrity (IBI) was a useful surrogate for mussel species richness and found the optimal spatial scale to describe associations between land use, stressors, and biota. These findings were used to structure the watershed risk analysis of relationships between sources, stressors, and effects.
Percent pasture area, percent crop land, and proximity to active mining, urban areas, or major transportation routes accounted for more than half of the variance in fish IBI scores, with coal mining having the most impact. Native fish and mussel populations appeared to be at greatest risk as more stressors co-occurred. Our results indicate that a number of sources and stressors are responsible for the decline in native species in the Clinch and Powell Valley watershed, but naturally vegetated riparian corridors may help mitigate some of these effects.
- (161 pp, 8 MB, about PDF)