Identifying land use changes and coal mining impacts on water quality: A case study across time and space
The spatial and temporal variability of water chemistry complicates the process of observing and identifying changes to water quality, particularly in catchments where data are spare. In this study, the effect of coal mining on water quality was assessed for the New River and upland, sub-catchment Indian Fork, in eastern Tennessee. Through the use of fragmented water quality and discharge records, hydrochemical trends were identified and compared between catchments and across time. Concentration-discharge relationships were characterized and recursive time-series modeling was completed to quantify long and short term hydrochemical trends. The inability of the New River 2007 time-series model to accurately perform under 1980 low-flow conditions suggests the basin wide shift in reclamation practices during the 1980s affected hydrologic pathways. Little temporal change was anticipated for the Indian Fork as mining ceased prior to available data, however hydrochemistry shifted from chemostatic to dilution response, likely due to spatial heterogeneity of the stream. The hydrochemical spatial disparity between the catchments is likely attributable to the percent of mining disturbed area within the New River (~7%) and Indian Fork (23%). Alternating c-Q loop rotation in the New River was found to be dependent on peak flows above (CW) or below (CCW) 25 m3/s discharge. Due to the magnitude of disturbance, the Indian Fork is conceptualized as a two component system: (1) impacted (i.e. spoil water) and (2) non-impacted water. The New River is conceptualized as a three component system: (1) impacted water, (2) non-impacted water, and (3) event water.