Location: Water Quality and Ecology ResearchTitle: Environmental flows in the context of unconventional natural gas development in the Marcellus Shale Author
|Walter, M. Todd|
Submitted to: Ecological Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2016
Publication Date: 8/29/2016
Publication URL: http://handle.nal.usda.gov/10113/63166
Citation: Buchanan, B.P., Auerbach, D.A., McManamay, R.A., Taylor, J.M., Flecker, A.S., Archibald, J.A., Fuka, D.R., Walter, M. 2016. Environmental flows in the context of unconventional natural gas development in the Marcellus Shale. Ecological Applications. doi:10.1002/eap.1425. Interpretive Summary: Increased access to natural gas supplies through unconventional natural gas development will enhance national energy independence, but may impact water availability for ecosystem needs if not properly managed. Resource managers need quantitative relationships between measures of stream flow alteration and ecosystem health to develop strategies for balancing environmental and energy needs for water. To address this need an ARS scientist in conjunction with researchers from Cornell University and the DOE examined relationships between fish communities and existing stream flow alteration across a 4 state region overlying the Marcellus Shale, an important natural gas bearing rock formation. Several measures of fish community health responded negatively to reductions in key components of stream flow. Evaluation of a range of surface water withdrawal scenarios stratified across stream size classes, suggest that larger streams will not be significantly impacted by water demands of unconventional natural gas development. However, headwater streams are at significant risk to flow impacts and associated declines in fish community health. These results confirm that shifting reliance of unconventional natural gas development on water from small to larger streams will help maintain high quality fish communities within the region.
Technical Abstract: Quantitative flow-ecology relationships are needed to evaluate the threat of water withdrawals associated with unconventional natural gas development to aquatic ecosystems. Addressing this need, we assessed current patterns of hydrologic alteration in the Marcellus Shale region by comparing observed stream flow attributes to those predicted under reference conditions. We then associated the estimated flow alteration with fish community metrics calculated from survey data. Finally, we evaluated scenarios of surface water withdrawal stratified across stream size classes and within the context of alternative environmental flow rules and observed flow-ecology relationships. Reduced high flow magnitudes, reduced rate of change, and increased low flow magnitudes were consistent regionally, but alteration in many of the flow metrics related to withdrawals varied substantially across locations. We found a number of significant relationships between flow alteration and ecological measures, including a decline in fish species richness with diminished annual runoff, winter low flow, and summer median flow. In addition, the relative abundance of intolerant taxa and cold headwater species decreased with reduced baseflow. The impact of withdrawal scenarios and the protection afforded by environmental flow standards were strongly related to stream size. Under the highest withdrawal scenario, approximately at least 90% of small streams showed a 30% reduction in summer flow, whereas little change is predicted for larger rivers. In addition, even under the lowest withdrawal scenario, summer flows were still reduced by 30% for at least 35% of headwaters. Observed flow-ecology relationships indicate that such alteration could reduce potential species richness by 40% or more. Variable passby flow standards and high fixed minimum flows limited alteration in the greatest number of streams, while common minimum flow standards resulted in substantial flow alteration in numerous streams. While further research is essential to understanding the effects of human water demands in the region, this study constitutes clear empirical support for measures to protect freshwater ecosystems by limiting or preventing water withdrawals from smaller streams.