Last month, the California Regional Water Quality Control Board, Central Valley Region (“Central Valley Water Board”) published a Food Safety Project White Paper (“White Paper”) on the use of oil field produced water for food crop irrigation. The White Paper did not find any evidence that using produced water for irrigation creates an elevated threat to human or crop safety.
When oil is extracted from the ground by oil wells, a portion of the fluid extracted generally consists of water. This portion is called produced water. According to the Central Valley Water Board, approximately 150 million barrels of oil are produced in California each year. One barrel contains 42 gallons of oil, and 10 to 15 gallons of produced water are extracted with each gallon of oil in the Central Valley.
The quality and suitability for irrigation of produced water depends on the area from which it is extracted. In Kern County, produced water has been used to irrigate crops for over three decades. The produced water is typically blended with other irrigation water before use. The Central Valley Water Board regulates use of produced water through waste discharge requirements, which include monitoring and reporting programs. Only five water management companies currently receive produced water for irrigation.
The White Paper is the culmination of a five-year study into the potential health risks of using produced water to irrigate food crops. The Food Safety Project received input from a volunteer panel of experts commissioned to provide technical guidance and recommendations. Public comments were also received during public meetings where the Food Safety Project’s work and findings were presented.
The White Paper summarizes three studies—denominated Tasks 1, 2 and 3—that were carried out by a neutral, third-party consultant. Task 1 identified chemicals potentially present in produced water and conducted a preliminary hazard evaluation of the chemicals to produce a “chemicals of interest” list for further evaluation. Task 2 conducted a comprehensive literature review of the identified chemicals of interest to evaluate the potential threat to human and crop safety. Task 3 compared the chemical composition of crop samples taken from crops irrigated using produced water with crop samples taken from conventionally irrigated crops over a three-year period. Central Valley Water Board staff, the expert panel, and a science advisor reviewed the reports for Tasks 1 through 3.
Among the findings presented in the White Paper were the following:
- Crop sample analyses indicated that the chemicals of interest that were measured in crops were all within the normal range of concentrations for food.
- The current monitoring requirements for produced water used for irrigation by the Central Valley Water Board is sufficiently rigorous.
- Tasks 1 through 3 did not yield any evidence that the reuse of produced water for irrigation poses an elevated threat to human health or crop safety.
The White Paper also identifies certain data gaps and includes findings and recommendations from the expert panel.
Implications and Conclusions
The Central Valley is home to one of the most productive agricultural regions in the world, irrigating more than 6.5 million acres. The Central Valley’s ability to meet its future water demand is impacted by both periods of severe drought and a growing population. According to a U.S. Bureau of Reclamation (“Reclamation”) report on the Sacramento and San Joaquin River Basins issued earlier this year, the three-year period from 2012 to 2015 was the driest period in the Central Valley’s recorded history. The Reclamation report also anticipates that the Central Valley’s population will almost double to 12 million by the year 2040. Future water supplies will thus be stressed by an increasing urban water demand.
California’s extended drought conditions and growing population will continue to impact the available irrigation water resources in the Central Valley and other areas of the state. As these conditions persist, produced water has the potential to become an important source of irrigation water. The White Paper indicates that the proximity of some oil and gas fields to agricultural lands and the quality of some produced water extracted from these fields makes produced water an ideal source of unconventional water for agricultural use. While the White Paper identified data gaps that require further research, its initial findings are promising. Indeed, given that 10 to 15 gallons of produced water are typically extracted per gallon of oil in the Central Valley, the potential benefits of further research into the viability and long-term effects of using produced water for irrigation purposes are self-evident. The White Paper paves the way for the Central Valley Water Board and other agencies and entities to conduct further studies into the expanded use of produced water for edible crop irrigation.
The reports for Tasks 1 through 3 and the expert panel’s recommendations are summarized in the White Paper and available in detail on the Central Valley Water Board’s website.
Reclamation’s report on the Sacramento and San Joaquin River Basins can be accessed here.