Bakersfield, California is where two of California’s biggest industries collide underground. Kern County produces more oil than any other county in the continental United States and is simultaneously one of the most productive agricultural counties in the country. Both industries have been pumping water out of — and putting contaminants into — the same aquifer system for over a century.
The result is a groundwater quality crisis that affects hundreds of thousands of people.
Oil and Water Don’t Mix (But They Do in Kern County)
Kern County has been producing oil since the 1890s. The region’s oil fields — including the massive Kern River, Midway-Sunset, and South Belridge fields — have generated billions of barrels of oil along with enormous volumes of produced water. Produced water is the salty, often chemical-laden water that comes up with oil during extraction.
For decades, much of this produced water was disposed of in unlined evaporation ponds or injected underground. In some areas, injection occurred into formations that weren’t adequately isolated from freshwater aquifers. The California Division of Oil, Gas, and Geothermal Resources identified hundreds of injection wells that may have been operating in protected aquifer zones.
The result: contamination of freshwater aquifers with petroleum compounds, heavy metals, and naturally occurring radioactive materials (NORM) associated with oil-bearing formations. Several small community water systems in Kern County have had to shut down wells due to contamination linked to oilfield operations.
Nitrate: The Valley’s Chronic Problem
Agriculture in Kern County is enormous — grapes, almonds, citrus, cotton, and dairy operations blanket the landscape. All that farming means massive amounts of nitrogen applied to the land as fertilizer and generated as animal waste.
The nitrate contamination of Kern County’s groundwater is severe and widespread. The State Water Resources Control Board has documented dozens of community water systems in the county that struggle with nitrate above the 10 mg/L MCL. Many of these serve small, disadvantaged communities — farmworker towns with limited tax bases and aging infrastructure.
The City of Bakersfield’s larger system has more resources to manage the problem through blending and treatment, but some of its wells produce water with elevated nitrate that must be blended down. The situation is worse in unincorporated areas surrounding the city.
1,2,3-TCP and Pesticide Legacy
Like the rest of the San Joaquin Valley, Kern County has widespread 1,2,3-TCP contamination from historic soil fumigant use. California’s 5 ppt MCL — the only standard in the nation for this contaminant — has revealed the scale of the problem.
Several Bakersfield-area water systems have had to take wells offline or install expensive GAC treatment systems to address TCP. The contamination is persistent and mobile in groundwater, meaning it will be a challenge for decades to come.
DBCP (dibromochloropropane), another agricultural pesticide banned in the late 1970s, is also present in Kern County groundwater. It’s a known carcinogen with an MCL of 0.2 ppb. Like TCP, it’s a ghost of agricultural practices from 50 years ago that continues to haunt the water supply.
Arsenic
Parts of Kern County have naturally elevated arsenic in groundwater — a geological reality across much of the arid West. The EPA’s MCL for arsenic is 10 ppb, and some wells in the Bakersfield area have tested close to or above that limit.
Arsenic at low levels has been linked to increased cancer risk, cardiovascular effects, and developmental issues. Treatment options exist (reverse osmosis, ion exchange, and specialized adsorptive media), but they add cost for water systems already struggling with nitrate and TCP.
Subsidence and Aquifer Stress
Kern County has experienced some of the worst land subsidence in California due to groundwater overdraft. In parts of the county, the land surface has dropped more than 10 feet since the 1920s. This subsidence permanently reduces the aquifer’s storage capacity and can change groundwater flow patterns, potentially pulling contaminated water into previously clean zones.
California’s SGMA requires local agencies to develop plans for sustainable groundwater management, but implementation in Kern County has been contentious. Agricultural interests, oil producers, and municipal water providers have competing demands on a shrinking resource.
What Residents Can Do
- Test your water. Whether you’re on municipal or private well water, know what’s in it. Minimum: nitrate, arsenic, bacteria, TCP.
- Invest in treatment. For most Bakersfield-area groundwater, a reverse osmosis system provides the broadest protection against the contaminant mix present here.
- Baby formula caution. If you have an infant, use purified or RO water for formula preparation. Nitrate is particularly dangerous for babies under 6 months (blue baby syndrome).
- Private well owners: You’re on your own for monitoring. California’s GAMA program can tell you what’s been detected in your area, but testing your specific well is essential.
- Advocate for cleanup. Kern County’s water quality problems are partly a regulatory failure. Community advocacy has driven improvements — the Agua Coalition and other groups have been effective at pushing for solutions.
If you’re concerned about your water quality, a certified water treatment professional can test your water and help you choose the right treatment system for the specific contaminants in your area.
For more Central Valley coverage, see Stockton water quality and Fresno water quality.
Sources: City of Bakersfield Water Resources, Kern County Water Agency, California State Water Resources Control Board, EPA SDWIS, USGS GAMA, California DOGGR