The California Division of Oil, Gas and Geothermal Resources recently closed 12 oil wells in the Central Valley because water used in the extraction process was being re-injected into underground aquifers. In a time of drought, these closures show the need for change in the management of California’s groundwater.

Water is used to create pressure and push oil toward the surface for extraction. The resulting wastewater, sometimes mixed with various chemicals as well as oil, is then re-injected into the ground, above the aquifer. The wastewater is partially cleaned as it seeps back down to the aquifer.

These reinjections raise concerns about drinking water contamination, though no instance has yet been identified. These worries are not due to any lack of regulation. In California, more than 30 state agencies regulate oil wells, including the Division of Oil, the California Air Resources Board and the California Water Resources Control Board.

At the federal level, the Environmental Protection Agency, Bureau of Land Management and Bureau of Safety and Environmental Enforcement also regulate injection wells. Rather than regulatory overreach, a better solution to possible aquifer contamination is to fully define property rights over groundwater.

Most water basins in California lack well-defined property rights. Groundwater rights are correlative, meaning landowners are allowed to extract water in proportion to the amount of land overlaying the underground aquifer. If a farmer has land that covers 15 percent of an aquifer, the farmer is entitled to 15 percent of the groundwater.

California should adjudicate its groundwater basins through a process in which the role of the courts is to define and enforce sustainable water rights. Such a system might take years to create, but it would result in more equitable water distribution, better-defined rights to the aquifer and ultimately wiser resource use. Moreover, this process extends legal protections over the aquifer, placing a check on businesses that may be polluting or exploiting the water body.

One example already in place is the San Bernardino basin area. Adjudicated since 1969, it has managed to preserve water through property rights.

Under adjudication, the basin has accelerated programs to help rid the water basin of pollution from a Lockheed Martin facility. Adjudication would provide similar benefits and protections if contamination were later detected at the Central Valley sites.

The extraction of oil, meanwhile, remains water-intensive. The adjudication process would further serve to provide cities with legal recourse if, say, an oil company were to pollute the groundwater. Almost 85 percent of Californians derive some drinking water from groundwater.

The closure of oil wells is a reminder that California should better define property rights over groundwater basins, a vital part of California’s water use and water storage infrastructure. With snowpack levels low, rain scarce and existing water reserves in question, the time to start the adjudication process is now.