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Impacts of Marcellus Shale Natural Gas Development on Surface Waters


William Penn Foundation, US Forest Service and others

Principal Investigator(s):

Drs. Jerry Mead, Assistant Research Professor, Biodiversity, Earth and Environmental Science, Watershed and Systems Ecology, Academy of Natural Science of Drexel University

Dr. Richard Horwitz, Professor, Biodiversity, Earth and Environmental Science, Fisheries, Academy of Natural Science of Drexel University

Dr. David Velinsky, Professor, Biodiversity, Earth and Environmental Science, Biogeochemistry, Academy of Natural Science of Drexel University

Dr. Don Charles, Professor, Biodiversity, Earth and Environmental Science, Phycology, Academy of Natural Science of Drexel University 

IExE Cluster:

Energy, Environment and Society


In the next ten years, approximately 24,000 wells for mining gas from the Marcellus Shale formation could be installed in Pennsylvania and adjoining states. Growing a greener economy requires substitutes for energies that have a large impact on environmental quality, like coal. However, drilling for natural gas may have a large impact on aquatic ecosystems, and the services that aquatic ecosystems provide people. Specifically, mining gas from the shale could impact stream ecosystems through a) withdrawals of water from streams and rivers; b) decreasing the quality of surface water from leakage of toxic frac-water returned from drilling the well; and c) declines in surface water quality associated with deforestation from building roads, laying pipes, building the well pads, and other construction activities. In a pilot study, the Academy of Natural Sciences of Drexel University (ANSD) found that the diversity of sensitive aquatic invertebrates was much less in streams with a high density of wells in its watershed than those in reference streams that had no wells within their watersheds. Yet the diversity in streams with a low density of wells in the catchment was not significantly different from the reference streams. Our findings were both alarming in the potential for major degradation in stream health in high well density watersheds, and promising in that the streams with a low density of wells in their watersheds had fewer environmental impacts.

In 2011, ANSD expanded their pilot study to streams in forested, public lands. These new sites have more stringent standards for drill pad site selection and construction than sites on private lands examined in the pilot study. The majority of the new sites are in the West Branch Susquehanna River and Pine Creek basins. The sites were stratified into three groups based on well pad density (WPD), with 10 reference, 11 lower density (0.2-0.35 well pads/km2), and 10 higher density (0.35-0.6 well pads/km2) sites. The maximum drill pad density was relatively low in these watersheds, relative to those in the pilot study. Water quality studies indicate that six sites had some correlation to Marcellus gas drilling, two of which also had evidence of coal mining. Moreover, sulfate concentrations in stream water were strongly correlated to WPD, particularly in ranges from 0.33 to 0.65 well pads/km2. The percentages of the diatom community with dominate types was positively correlated and the Shannon-Weiner index of diversity was negatively correlated to WPD. In addition, the diatom indicator of calcium was also related to WPD. However, selected stream macro-invertebrate, crayfish, and fish metrics were not significantly correlated to WPD. ANSD continues to monitor the field sites to assess the potential impacts of Marcellus drilling activities on surface waters as development progresses.