Large-sample evidence on the impact of unconventional oil and gas development on surface waters

Lightly salted surface waters Hydraulic fracturing uses a water-based mixture to open up tight oil and gas formations. The process is mostly contained, but concerns remain about the potential for surface water contamination. Bonetti et al . found a small increase in certain ions associated with hydraulic fracturing across several locations in the United States (see the Perspective by Hill and Ma). These small increases appeared 90 to 180 days after new wells were put in and suggest some surface water contamination. The magnitude appears small but may require that more attention be paid to monitoring near-well surface waters. —BG