Mountaintop mining makes streams saltier and more perennial, study in W.Va. watershed finds

Map shows mined areas in red and a star on study area.

Mountaintop-removal coal mining has made the streams of West Virginia's Mud River basin run saltier but more regularly, researchers at Duke University and the University of Wyoming have found.

It has long been known that excavation of rock around coal seams, which is then placed into engineered fills at stream headwaters, releases salty substances into streams. But the study also confirmed something that has long been surmised, that "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 stream flows during the drier months that make up about 80 percent of the region's calendar year, says a UW press release published in Science Daily.

3-D map and chart in study compare streamflow in mined and non-mined areas.

The more frequent flows in ephemeral streams mean that the Mud River and its tributaries, "the site of extensive mountaintop mining in recent years . . . run consistently saltier for up to 80 percent of the year," the release says. That "has implications for farming, urban water use and the environment, as well as degradation of streamwater quality," says Matthew Ross, a Ph.D. student at Duke's Nicholas School of the Environment. His co-author is Fabian Nippgen, assistant professor of ecosystem science and management at UW. Their study was published this week in the journal Environmental Science & Technology. "It is among the first studies to document mountaintop-removal coal mining's long-term impacts on watershed, and to show how mined areas contribute to local and regional stream flow," the release says.