Development of energy and mineral resources in the Powder River structural basin in northeastern Wyoming and southeastern Montana (fig. 1) includes coalbed natural gas, conventional oil and gas, and coal mining. A common byproduct of coalbed natural gas (CBNG) development is discharge of groundwater that commonly is saline or unsuitable for irrigation of crops and has unknown effects on the aquatic communities inhabiting streams that receive the water (Bureau of Land Management, 2009).