The effects of surface coal mining on the water quality, sediment discharge, and aquatic biology of streams in the Stony Fork Basin in southwestern Pennsylvania were studied from 1978 through 1985. Data were collected at five stream sites and one mine discharge site. Field data included streamflow, temperature, specific conductance, pH, acidity, and alkalinity. Laboratory analyses included sulfate, aluminum, iron, manganese, zinc, and selected trace elements.
Annual streamflow at gaged sites was not substantially different, suggesting that mining did not affect the total volume of streamflow significantly. Comparisons of sediment yields of the upstream control site (site 5) to the downstream site (site 1) indicated that the sediment yield at site 5 was greatest in 1978, 1981-83, and 1985. The sediment yields at both sites in 1979-80 were about the same. Differences in the drainage area sizes and effective control of sediment in the mined areas may explain the lack of increased sediment yield at the downstream site.
As mining became more extensive throughout the basin in 1979-80 and later, several water-quality effects were observed downstream. Generally, specific conductance, sulfate, manganese, aluminum, and zinc increased; pH and alkalinity decreased. Acidity and iron typically increased immediately downstream of mined areas. No trace-element concentrations exceeded maximum contaminant levels established by the U.S. Environmental Protection Agency.
Surface mining in the Stony Fork Basin severely affected the stream invertebrate and fish populations. During 1977-84, the number of taxonomic groups of invertebrates at sites affected by mine drainage decreased by 45 to 71 percent; the number of fish species decreased by 81 to 88 percent.
