In the last few years, tens of thousands of hydraulic fracturing wells from Pennsylvania to Texas to North Dakota have undertaken unconventional oil and gas production, becoming part of daily routine for many Americans.
This poses questions about the effects of this activity on local communities and human health. A study published in the journal Science has revealed that hydraulic fracturing can contaminate groundwater and lower surface water quality.
The study observes that hydraulic fracturing is related to small increases in salt concentrations of surface waters for many shales and watersheds across the United States. Huge effects have occurred during the early stages of production, where wells produce large amounts of flow back and produce water. But according to the U.S. Environmental Protection Agency, the highest levels lie well below the harmful status.
Our work provides the first large-sample evidence showing that hydraulic fracturing is related to the quality of nearby surface waters for several U.S. shales. Though we estimated very small water impact, one has to consider that most measurements were taken in rivers or streams and that the average fracturing well in our dataset was not particularly close to the monitors in the watershed.
Christian Leuz, Study Co-Author and Joseph Sondheimer Professor of International Economics, Finance and Accounting, Booth School of Business, University of Chicago
Leuz and his co-authors, Pietro Bonetti from the University of Navarra and Giovanna Michelon from the University of Bristol, merged surface water measurements with more than 46,000 hydraulic fracturing wells. This was to assess whether new drilling and developmental activities are linked with increased salt concentration (bromide, chloride, barium, and strontium) in 408 watersheds spanning 11 years.
They observed a small but constant increase in chloride, barium, and strontium. However, bromide increase was not detected in the watershed with new hydraulic fracturing wells.
Many studies support the correlation between the increased salt level and the nearby hydraulic fracturing activities. Considering when the highest levels occurred, salt concentration was also high for wells in regions where the deep formation showed increased salinity levels.
Furthermore, the levels were highest when traced within a year at monitoring stations located 15 km and probably downstream from a well.
Better and more frequent water measurement is needed to fully understand the surface water impact of unconventional oil and gas development.
Pietro Bonetti, Study Co-Author, University of Navarra
Bonetti also stated that the lack of water quality data posed a hindrance to the analysis.
Hydraulic fracturing fluids hold chemical substances with more dangerous properties than salts. However, those are not commonly included in public databases, which causes difficulty in making large-sample statistical analyses. Also, many monitoring stations in a watershed are not situated near wells or may be upstream from the well. This depresses the magnitude of the estimates.
Policymakers could consider more targeted water measurement. For instance, policymakers could place monitoring stations in locations where they can better track surface water impacts, increase the frequency of measurement around the time new wells are drilled, and more systematically track the other chemical substances found in fracking fluids.
Giovanna Michelon, Study Co-Author, University of Bristol
Bonetti, P., et al. (2021) Large-sample evidence on the impact of unconventional oil and gas development on surface waters. Science. doi.org/10.1126/science.aaz2185.