The Appalachian Landscape Conservation Cooperative recently concluded a project with the New York Cooperative Fish and Wildlife Research Unit and Cornell University to assess the impact of hydraulic fracturing on streams. Hydraulic fracturing has been used in portions of Pennsylvania and West Virginia to increase production of natural gas and there are potential implications for portions of Ohio and New York as well. The study focused on the Marcellus Shale deposit, a geographically expansive shale gas reservoir estimated to contain over 13 trillion cubic feet of recoverable natural gas. The recent development of horizontal drilling and hydraulic fracturing has allowed for the rapid expansion of natural gas drilling in the Marcellus Shale region.

The development of a typical gas well requires millions of gallons of water often obtained from surface water withdrawal in nearby streams. Hundreds of gas wells have recently been drilled in the region with potentially thousands more in the relatively near future. To evaluate the impacts of these water withdrawals, the team of scientists developed models that predicted ecological responses to changes in stream flow and performed an analysis to evaluate the potential range of effects stemming from water withdrawals. They then predicted the relative risk of streams to alterations due to hydraulic fracturing withdrawals, and evaluated the effectiveness of various withdrawal restrictions.

The team determined that a considerable number of streams are at high risk of flow alteration due to withdrawals during the summer and fall seasons ? especially smaller streams in the southwestern (western portions of Ohio River Basin) and northern (headwaters of the Upper Susquehanna and Hudson River Basins) sections of the region.  Though these high-risk streams are individually small, combined they drain the majority of the study region. Additionally, they found conventional minimum flow standards either provided inadequate ecological protection or may prove overly restrictive in terms of meeting human water requirements. Flow standards that vary according to stream size and season appeared to provide the best balance between ecological and human water needs.

A complicated and largely inconsistent regulatory framework has taken shape in the region with existing laws and regulations created, monitored and enforced by a combination of state agencies and river basin commissions. The hope is this research will be used as a basis for the development of region-wide policies to protect stream ecosystems and enhance long-term management of the aquatic resources found there. A number of specific recommendations for managers were provided as a result of this research and include:

• Surface water withdrawals at the scale of individual streams, especially headwaters during the summer and fall, can be considerable and must be appropriately managed to ensure that human water needs are well balanced with those of aquatic ecosystems
• Environmental flow standards and monitoring campaigns should account for the fact that fish respond not just to alterations in low flows, but also to alteration in a variety of flow components (seasonal, low, median and high flows)
• Smaller watersheds should be prioritized for hydraulic fracturing related flow standards; and
• Flow standards that vary with stream size and season provide the best compromise between ecologic water requirements and water needs for shale gas development.

View more information on this project.