Kern County produces more oil than any other county in California and ranks among the top agricultural counties in the nation. It also has some of the most contaminated groundwater in the state. Those facts are not a coincidence.
The county’s roughly 900,000 residents — concentrated in Bakersfield and scattered across dozens of smaller communities — depend heavily on groundwater. And that groundwater has been under assault from both above and below for decades.
Two Industries, One Aquifer
Kern County sits atop the southern end of the San Joaquin Valley’s vast aquifer system. The same geological formations that hold water also hold oil, and the boundary between the two isn’t always as clear as you’d hope.
Oil production in Kern County has been ongoing since the late 1800s. The county contains some of California’s largest oil fields, including the Kern River, Midway-Sunset, and South Belridge fields. Oil extraction generates enormous volumes of produced water — wastewater that comes up with the oil. This produced water contains salts, heavy metals, naturally occurring radioactive materials, and petroleum hydrocarbons.
For decades, produced water was disposed of in unlined surface ponds or injected underground. Some of it ended up in aquifer zones that connect to drinking water supplies. The state has been tightening regulations on produced water disposal, but the legacy contamination remains.
Agriculture is the other major source. Kern County farms grow almonds, grapes, citrus, pistachios, carrots, and cotton — all of it irrigated. The fertilizers, pesticides, and animal waste that come with large-scale agriculture have pushed nitrate levels in the aquifer to dangerous concentrations.
The Nitrate Crisis
Nitrate contamination is arguably the most widespread and immediate threat to Kern County’s drinking water. The fertilizers applied to millions of acres of farmland leach nitrogen into the soil, where it converts to nitrate and percolates into the aquifer.
The federal MCL for nitrate is 10 mg/L (milligrams per liter). In many parts of Kern County — particularly the rural communities between Bakersfield and the Tehachapi Mountains — well water regularly exceeds that limit. Some wells have tested above 20 mg/L.
Nitrate is particularly dangerous for infants. High nitrate levels can cause methemoglobinemia, commonly known as “blue baby syndrome,” which interferes with the blood’s ability to carry oxygen. For adults, long-term exposure has been linked to increased cancer risk.
Small community water systems and private well owners in rural Kern County are disproportionately affected. Many of these systems lack the resources to install nitrate treatment, and private wells have no regulatory requirement for testing.
The 1,2,3-TCP Problem
1,2,3-Trichloropropane (TCP) is a legacy pesticide fumigant that has contaminated groundwater across the San Joaquin Valley. California set an MCL of 5 parts per trillion in 2017 — one of the strictest standards for any contaminant in the state.
TCP is persistent, meaning it doesn’t break down easily in groundwater. It’s also difficult and expensive to treat. Some small water systems in Kern County have had to shut down wells or invest in granular activated carbon treatment to meet the standard.
Groundwater Status Changes
In February 2025, changes to the designation of certain groundwater basins in Kern County under the Sustainable Groundwater Management Act (SGMA) raised concerns among longtime farm families. Reclassification of basin status can trigger additional regulations on pumping, monitoring, and water quality — which some agricultural operators worry will lead to restrictions on their operations while doing little to address the pollution already in the aquifer.
The tension between agricultural interests and water quality protection is central to Kern County’s water future. SGMA requires basins to reach sustainability by 2040 or 2042, depending on their priority level, but critics argue the timelines are too slow to protect current drinking water users.
What Kern County Residents Should Do
- Test your water. If you’re on a private well in rural Kern County, test for nitrates, TCP, and total dissolved solids at minimum. The Kern County Environmental Health Division can direct you to certified labs.
- Know your water system. If you’re on a community water system, request the most recent water quality report. Systems serving fewer than 10,000 people may have less treatment capacity.
- Consider treatment. Reverse osmosis systems are effective against nitrates, TCP, and most agricultural and petroleum contaminants. For well owners in high-nitrate areas, this is the most reliable protection available.
- Follow SGMA developments. Groundwater sustainability plans will shape Kern County’s water future for decades. Public comment periods and board meetings are your chance to weigh in.
If you’re concerned about your water quality, a certified water treatment professional can test your well or tap water and recommend a system that addresses Kern County’s specific contamination profile. Given the dual pressures of agriculture and oil production, proactive testing isn’t optional — it’s essential.
Related Reading
- Bakersfield CA Water Quality: Oil Fields and Agriculture
- Fresno Water Quality: Nitrate and 1,2,3-TCP Contamination
- Stockton CA Water Quality: Delta Water and Nitrate
- South Gate CA Water Quality: Industrial Legacy Contamination
Sources
- California State Water Resources Control Board groundwater quality data
- Kern County Environmental Health Division well monitoring reports
- USGS San Joaquin Valley groundwater quality assessments
- California Department of Conservation oil and gas production data
- Sustainable Groundwater Management Act basin priority designations