Creating a More Perennial Problem? Mountaintop Removal Coal Mining Enhances and Sustains Saline Baseflows of Appalachian Watersheds

Abstract

Mountaintop removal coal mining (MTM) is a form of surface mining where ridges and mountain tops are removed with explosives to access underlying coal seams. The crushed rock material is subsequently deposited in headwater valley fills (VF). We examined how this added water storage potential affects streamflow using a paired watershed approach consisting of two sets of mined and unmined watersheds in West Virginia. The mined watersheds exported 7-11% more water than the reference watersheds, primarily due to higher and more sustained baseflows. The mined watersheds exported only ~1/3 of their streamflow during storms, while the reference watersheds exported ~2/3 of their annual water yield during runoff events. Mined watersheds with valley fills appear to store precipitation for considerable periods of time and steadily export this alkaline and saline water even during the dry periods of the year. As a result, MTMVFs in a mixed mined/unmined watershed contributed disproportionately to streamflow during baseflow periods (up to >90% of flow). Because MTMVFs have both elevated summer baseflows and continuously high concentrations of total dissolved solids, their regional impact on water quantity and quality will be most extreme and most widespread during low flow periods.

Spatial Convergence in Major Dissolved Ion Concentrations and Implications of Headwater Mining for Downstream Water Quality

“…All others, including TDS are mg/L. The water chemistry and hydrology of streams draining MTM/VF operations tend to be more stable than unmined forested streams due to increased storage in fill materials and presence of sediment ponds below fills that dampen stormflows (Griffith et al 2012;Zegre et al 2014;Nippgen et al 2017). Our findings further demonstrate that headwater streams are more variable in water chemistry, both spatially and temporally, than downstream waters.…”

“…As a result, dissolved ion concentrations, measured as stream conductivity, are often more than 100 times greater in MTM/VF streams than in unmined streams of the region (Bryant et al 2002;Fritz et al 2010;Johnson et al 2010). Numerous studies have now demonstrated adverse impacts of elevated conductivity from MTM/VF activities to stream biota (e.g., Merricks et al 2007;Pond et al 2008;Pond 2010), water chemistry (Griffith et al 2012), hydrology (Ferrari et al 2009;Zegre et al 2014;Nippgen et al 2017), and other environmental consequences (Palmer et al 2010;Bernhardt and Palmer 2011). Numerous studies have now demonstrated adverse impacts of elevated conductivity from MTM/VF activities to stream biota (e.g., Merricks et al 2007;Pond et al 2008;Pond 2010), water chemistry (Griffith et al 2012), hydrology (Ferrari et al 2009;Zegre et al 2014;Nippgen et al 2017), and other environmental consequences (Palmer et al 2010;Bernhardt and Palmer 2011).…”

Excess Nitrate Export in Mountaintop Removal Coal Mining Watersheds

“…All settlement ponds at Ballard Fork had been filled in by the time of the study. The Reference watershed is a forested 118‐ha tributary to the nearby Left Fork Mud River and was selected for its comparable size and geology to the Laurel Branch watershed (Nippgen et al, ). Unfortunately, there are no other long‐term watershed studies in this region to provide additional estimates of NO 3 − flux; however, mean NO 3 − concentrations for our Reference site (0.24 mg N L −1 ) are similar to mean concentrations at unmined watersheds reported in other studies in the region: 0.22 mg N L −1 (Lindberg et al, ) and 0.4 mg N L −1 (Pond et al, ).…”

“…The resulting landscapes are regraded, but resulting watersheds are significantly flatter and more porous than before mining (Miller & Zégre, ; Ross et al, ). The resulting changes in topography, subsurface structure, and porosity alter hydrologic flow paths and can turn intermittent headwaters into perennial streams (Evans et al, ; Nippgen et al, ). These alterations coupled with the increased surface area of mine spoils drive high mineral weathering rates, leading to shifts in stream chemistry that propagate downstream of the mine permit boundaries as alkaline mine drainage (AlkMD) (Lindberg et al, ; Ross et al, ).…”

A Review of Fine-Scale Land Use and Land Cover Classification in Open-Pit Mining Areas by Remote Sensing Techniques

“…Miller and Zégre [100] provided insights into the complexity of catchment hydrology in a mountaintop removal-mining region. Nippgen et al [101] examined saline baseflows of the Appalachian Watersheds affected by mountaintop removal coal mining. Brooks [102] evaluated the impact of mountaintop mining on the watershed and regional scale nitrogen exports.…”