Mountaintop-removal coal mining causes many streams and rivers in Appalachia to run consistently saltier for up to 80 percent of the year, a new study by researchers at the University of Wyoming and Duke University finds.
The scientists examined water quality in four watersheds that flow into southern West Virginia’s Mud River basin, the site of extensive mountaintop mining in recent years. In mountaintop-removal mining, underground coal seams are exposed by blasting away summits or ridges above them. Any leftover debris and crushed rocks are deposited in neighboring valleys, creating “valley fills” that can stretch for long distances and bury entire streambeds.
“Over time, alkaline salts and other contaminants from the coal residue and crushed rocks in these valley fills leach into nearby streams and rivers, degrading water quality and causing dramatic increases in salinity that are harmful to downstream ecosystems,” says Fabian Nippgen, assistant professor of ecosystem science and management at UW.
To compound matters, the porosity of the crushed rocks increases the water storage capacity of the valley fills. This decreases natural storm runoff during high-flow winter months while contributing proportionately more water to streamflows during the drier months that make up about 80 percent of the region’s calendar year.
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