Mining and residential development interact to produce highly impaired stream conditions in an intensively mined Appalachian watershed

Large scale surface mining in southern West Virginia causes significant alteration of headwater stream networks.  It is unclear, however, the extent to which mining interacts with other stressors to determine conditions in aquatic systems downstream.  Through a watershed scale assessment, the specific objectives of this study were to:  1) develop landscape-based indicators of mining and residential development; 2) quantify the interactive effects of mining and residential development on in-stream conditions; and 3) identify landscape-based thresholds above which biological impairment occurs in intensively mined watersheds.  Analyses indicate that mining resulted in more acute changes in water chemistry, whereas residential development had a stronger impact on both physical habitat and macroinvertebrate community structure.  The combined effects of mining and development on in-stream conditions were additive.  The degree of impairment observed at a given level of mining was directly proportional to the intensity of residential development and vice versa.  Impairment thresholds were observed at ~25% total mining (conductivity of ~100µS/cm) and at parcel densities of ~5 and 14parcels/km².  Our results provide a tool that can be used to predict ecological response to proposed levels of mining given pre-existing landscape conditions.  Furthermore, effective management in these systems must address the prevalence of non-mining related impacts.