The potential for impacts on water resources is often recognized as an important issue when shale gas development is discussed. Potential and significant impacts on groundwater and surface water resources might arise by wellbores traversing drinking-water aquifers, the use of significant water inputs, and the generation of large wastewater streams. Water withdrawals for energy development could reduce instream flows in rivers and streams, or reduce groundwater levels, diminishing ecosystem services—such as species habitat, recreation, and pollution assimilation— and reducing water available for other diverted uses. Water pollution from shale gas development could reduce or degrade the quality of available resources for uncompensated downstream users who divert water from shared rivers and streams, or users of a common aquifer. Accidental releases are one avenue for these impacts. Liquid waste treatment and disposal is another. Recent research is beginning to shed more light to better inform public concerns.