SURFACE COAL MINING IMPACTS ON CONCENTRATION-DISCHARGE RELATIONSHIPS: IDENTIFYING SPATIAL AND TEMPORAL CHANGES IN THE NEW RIVER, TENNESSEE

Surface mining for coal substantially alters land-use and subsequently perturbs pre-established hydrologic pathways within a watershed. On the Appalachian Plateau, decades of coal mining have produced large volumes of spoil for which various reclamation practices have been implemented. For watersheds with circumneutral pH, sulfate and specific conductivity are efficient proxies for evaluating the influence of coal mining on water chemistry and, concentration-discharge (C-Q) relationships prove a useful tool for identifying spatial and temporal changes. We examined C-Q relationships for the New River watershed and Indian Fork tributary, located in eastern Tennessee, using historic (1975-1982) and recent (2007-2009) water chemistry and streamflow data. Long term C-Q relationships were explored by linear regression of log-transformed concentration and discharge data. C-Q plots also were used to examine episodic relationships. A significant change in slope of the regression lines from historic to recent time periods in the Indian Fork indicates a decrease in available sulfate with time because mining ceased in 1972. Episodic C-Q plots indicate that below a 25 m³/s peak flow the response of solute concentration in the New River is to increase with discharge whereas the opposite (dilution) occurs for peaks above that threshold. Based on different reclamation methods and the percent of mining-disturbed area the New River (7%) and Indian Fork (23%), two and three component mixing models are presented, respectively. Solute concentrations in the Indian Fork are conceptualized as the mixing of: (1) impacted (i.e. spoil water) and (2) event water; the New River has an additional component (3) of non-impacted water.