title: Environmental flows in the context of unconventional natural gas development in the Marcellus Shale.
abstract: Quantitative flow-ecology relationships are needed to evaluate how water withdrawals for unconventional natural gas development may impact aquatic ecosystems. Addressing this need, we studied current patterns of hydrologic alteration in the Marcellus Shale region and related the estimated flow alteration to fish community measures. We then used these empirical flow-ecology relationships to evaluate alternative surface water withdrawals and environmental flow rules. Reduced high-flow magnitude, dampened rates of change, and increased low-flow magnitudes were apparent regionally, but changes in many of the flow metrics likely to be sensitive to withdrawals also showed substantial regional variation. Fish community measures were significantly related to flow alteration, including declines in species richness with diminished annual runoff, winter low-flow, and summer median-flow. In addition, the relative abundance of intolerant taxa decreased with reduced winter high-flow and increased flow constancy, while fluvial specialist species decreased with reduced winter and annual flows. Stream size strongly mediated both the impact of withdrawal scenarios and the protection afforded by environmental flow standards. Under the most intense withdrawal scenario, 75% of reference headwaters and creeks (drainage areas <99 km2) experienced at least 78% reduction in summer flow, whereas little change was predicted for larger rivers. Moreover, the least intense withdrawal scenario still reduced summer flows by at least 21% for 50% of headwaters and creeks. The observed 90th quantile flow-ecology relationships indicate that such alteration could reduce species richness by 23% or more. Seasonally varying environmental flow standards and high fixed minimum flows protected the most streams from hydrologic alteration, but common minimum flow standards left numerous locations vulnerable to substantial flow alteration. This study clarifies how additional water demands in the region may adversely affect freshwater biological integrity. The results make clear that policies to limit or prevent water withdrawals from smaller streams can reduce the risk of ecosystem impairment.
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York, 14853, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Buchanan
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14853, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Auerbach
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: McManamay
authors.affiliation: Water Quality and Ecology Research Unit, USDA-ARS National Sedimentation Laboratory, Oxford, Mississippi, 38655, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Taylor
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14853, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Flecker
authors.affiliation: Department of Civil and Environmental Engineering, Seattle University, Seattle, Washington, 98195, USA.
authors.forename: Josephine A
authors.initials: JA
authors.lastname: Archibald
authors.affiliation: Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia, 24061, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Fuka
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York, 14853, USA.
authors.forename: M Todd
authors.initials: MT
authors.lastname: Walter
mesh_terms: D000818:Animals; D001061:Appalachian Region; D058448:Biota; D005399:Fishes; D000067071:Hydraulic Fracking; D062070:Hydrology; D059206:Natural Gas; D000066388:Oil and Gas Industry; D045483:Rivers; D014872:Water Movements
chemical_list: D059206:Natural Gas
keywords: Appalachia; Marcellus Shale; environmental flows; fish; flow regime; hydraulic fracturing