STREAM RESPONSE TO CHANGING WEATHER PATTERNS IN SOUTHWESTERN PENNSYLVANIA

Tenmile Creek, a tributary of the Monongahela River, is the boundary between Greene and Washington Counties in southwestern Pennsylvania, with headwaters of the North and South Forks near the border with West Virginia. The stream is an important freshwater resource for the region. Situated in the heart of coal country and the shale gas footprint of western Appalachia, the stream has a legacy of challenges to its flow and water quality. Over the past two years, but particularly during the spring and summer of 2018, the region has experienced wetter conditions than previous years going back to 2010. In fact, 2018 has been the fourth wettest year on record for the Pittsburgh region, just to the north. Since late 2016, Tenmile Creek has experienced six flow events of more than 7000 cfs and two events measured over 11000 cfs. In the six years prior, there are only two events that approached the 7000 cfs threshold. Additionally, discharge has only dropped below 10 cfs one time since late 2016, though not uncommon in prior years. As a result, concerns about enhanced erosion and mass wasting and the corresponding impacts to infrastructure and near-stream property have risen. Impacts to water quality are dubious. Conductivity values have been trending lower, possibly due to dilution of the groundwater that has historically elevated the stream’s dissolved load. Most streams in the area, and Tenmile is no exception, tend to respond quickly to rain events due to steep topography and clay-rich soils. Facing the uncertainty of changing weather patterns due to climate change, the region must reassess water management to account for more consistently high flows.