Assessment of Aquatic Communities in Northeastern Wyoming and Southeastern Montana

The Powder River Structural Basin (PRB) in northeastern Wyoming and southeastern Montana is an important source of energy resources for the United States. Resources developed from the basin include coal, oil, uranium, conventional natural gas, and within the last decade coal-bed natural gas (CBNG) which often is referred to as coal-bed methane. As of 2008, about 20,000 CBNG wells had been drilled in northeastern Wyoming (Wyoming Oil and Gas Conservation Commission, 2010). An estimated 50,000 to 60,000 CBNG wells could be drilled and put into production in the PRB by 2012. Throughout the PRB large volumes of groundwater are removed from coal-bed aquifers and discharged on the surface in order to recover CBNG. This groundwater, which can be slightly to moderately saline, is discharged to perennial, intermittent and ephemeral streams as well as to surface impoundments. It is currently unknown what potential impacts these discharges will have on aquatic communities (fish, macroinvertebrates, and algae) and their habitats.