Vulnerability of Groundwater Resources Underlying Unlined Produced Water Ponds in the Tulare Basin of the San Joaquin Valley, California

The
San Joaquin Valley (SJV) in California is one of the most agriculturally
productive regions in the world relying in part on groundwater for
irrigation and for domestic or municipal water supply for nearly 4
million residents. One area of growing concern in the SJV is potential
impact to groundwater resources from ongoing and historical disposal
of oilfield-produced water into unlined produced water ponds (PWPs).
In this investigation, we utilized available information on composition
of produced water disposed into unlined PWPs and levels of total dissolved
solids in underlying groundwater to demonstrate that this disposal
practice, both past and present, poses risks to groundwater resources,
especially in the Tulare Basin in the southern SJV. Groundwater monitoring
at unlined PWP facilities is relatively sparse, but where monitoring
has occurred, impact to aquifers used for public and agricultural
water supply has been observed and has proven to be too expensive
to actively remediate. Results of this investigation should inform
policy discussions in California and other locations where disposal
of produced water into unlined impoundments occurs, especially at
locations that overlie groundwater resources.