California citrus growers and other farmers in the Bakersfield area may feel vindicated with the result of a new study by researchers at Duke University and RTI International. As reported in the California Department of Food and Agriculture Planting Seeds blog, the study finds that reusing oilfield water that’s been mixed with surface water to irrigate farms in the Cawelo Water District of Kern County does not pose major health risks, as some opponents of the practice have feared.
“We did not find any major water-quality issues, nor metals and radioactivity accumulation in soil and crops, that might cause health concerns,” said Avner Vengosh, professor of water quality and geochemistry at Duke’s Nicholas School of the Environment, whose lab led the new study.
Faced with increasing droughts and water shortages, some farmers in the Cawelo district have used diluted oilfield produced water (OPW) for irrigation for their fields for more than 25 years, as permitted under California Water Board policy.
A study released in 2016 by the Cawelo Water District showed no uptake of the organic elements found in OPW into fruit. A third-party environmental toxicologist conducted the study.
While the oilfield-mixed water contains slightly elevated levels of salts and boron relative to the local groundwater, those levels are still below the standards set by the state for safe drinking water and irrigation in the Cawelo district, Vengosh said.
Boron and salts from the OPW have, however, accumulated over time in the irrigated soil. The district’s farmers will need to plant boron-tolerant crops and keep mixing the OPW with fresh water to avoid boron toxicity and salinity buildup in their fields and to remain within state guidelines. “But all things considered, this is good news,” Vengosh said.
The researchers explained that the study only applies to OPW produced in the study’s area. There are significant differences between Kern OPW and the OPW produced at other oilfields around the country.
“The OPW produced in Kern County is much more diluted and low-saline than common OPW from other parts of the country. So, it can be used for irrigation if it is mixed with surface water,” said Andrew Kondash, a research environmental scientist at RTI International, who led the study as part of his 2019 doctoral dissertation at Duke.
Determining whether it is safe to use OPW for irrigation in other locations would require water and soil testing, Kondash said. “You can’t assume that the results in this study could be applied to OPW from other oilfields, where the salinity is typically much higher.”
The researchers published their peer-reviewed findings May 18 in the journal Science of the Total Environment. The study was part of a research project funded by the U.S. Department of Agriculture National Institute of Food and Agriculture.
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