Bakersfield is where California’s two biggest industries — agriculture and oil — meet in the same aquifer. Kern County produces more petroleum than any other county in the lower 48 states and simultaneously ranks as one of the nation’s top agricultural counties by crop value. Both industries depend heavily on water, and both have left deep marks on the groundwater that 400,000 Bakersfield-area residents rely on.
Two Industries, One Aquifer
The Kern County Sub-basin of the San Joaquin Valley Groundwater Basin underlies Bakersfield and the surrounding agricultural and oil-producing areas. This aquifer system provides the majority of the region’s drinking water — the city operates dozens of municipal wells drawing from varying depths.
The problem is that both agriculture and oil production have been contaminating this aquifer from above for over a century. The contamination comes from different sources but converges in the same groundwater that supplies taps across the metro area.
California Water Service (Cal Water) and the City of Bakersfield’s water departments operate the municipal systems, treating groundwater with varying levels of technology depending on the specific well and its contamination profile. Some wells have needed advanced treatment; others have been shut down entirely.
Oil Production: A Century of Groundwater Impact
Kern County’s oil fields — including the enormous Kern River, Midway-Sunset, and South Belridge fields — have been in production since the early 1900s. The environmental practices of that era were, to put it diplomatically, different from today’s.
Produced water — the brackish, often toxic fluid that comes up with oil — was for decades disposed of in unlined surface ponds or injected into shallow formations with minimal oversight. This produced water typically contains elevated levels of naturally occurring arsenic, boron, barium, and benzene, along with treatment chemicals added during the extraction process.
The State Water Resources Control Board has documented cases where oil field produced water migrated into or contaminated freshwater aquifers in Kern County. A 2015 investigation revealed that the state’s Division of Oil, Gas, and Geothermal Resources (DOGGR, now CalGEM) had permitted injection wells that were operating in or near protected aquifer zones — essentially allowing waste disposal into drinking water sources.
The fallout from that revelation led to emergency orders, well closures, and enhanced monitoring requirements. But the legacy contamination — potentially decades of produced water disposal into or near freshwater zones — is in the ground and moving slowly through the aquifer.
Agricultural Contamination: Nitrate, DBCP, and 1,2,3-TCP
Bakersfield is surrounded by some of the most productive agricultural land in the world. Almonds, pistachios, grapes, citrus, carrots, potatoes — the list goes on. Irrigating these crops in a semi-arid climate requires enormous volumes of water, and the associated fertilizer and pesticide applications have consequences for groundwater.
Nitrate is the most widespread agricultural contaminant in the Bakersfield area. Decades of synthetic nitrogen fertilizer application, combined with dairy and feedlot operations in Kern County, have pushed nitrate levels in the shallow aquifer well above the EPA MCL of 10 mg/L as nitrogen in many areas. The UC Davis Center for Watershed Sciences has identified the Tulare Lake Basin — which includes Kern County — as the most nitrate-impacted groundwater region in California.
DBCP (dibromochloropropane), the banned soil fumigant, remains detectable in wells throughout the southern San Joaquin Valley. Bakersfield-area wells have required treatment or closure due to DBCP, and the contamination will persist for decades given the chemical’s slow degradation rate in groundwater.
1,2,3-TCP (trichloropropane) is a particularly pernicious contaminant in the Bakersfield area. An impurity in soil fumigant products used heavily in Kern County agriculture, 1,2,3-TCP is a probable human carcinogen with California’s MCL set at an extremely low 5 parts per trillion. At that detection threshold, contamination is widespread — multiple Bakersfield-area water systems have had to install granular activated carbon treatment or take wells offline.
The responsible chemical companies — Shell and Dow, primarily — have faced extensive litigation over DBCP and 1,2,3-TCP contamination in the Central Valley. Legal settlements have funded some treatment infrastructure, but the scale of contamination far exceeds what litigation alone can address.
Drought and SGMA: The Sustainability Reckoning
Kern County’s groundwater has been in overdraft for decades — more water pumped out than is replenished naturally. During California’s severe droughts (2007-2009, 2012-2016, and 2020-2022), agricultural pumping intensified as surface water deliveries from the State Water Project and Central Valley Project were curtailed.
The consequences are visible: land subsidence of 1-2 feet in parts of Kern County, falling water tables, increased pumping costs, and — critically for water quality — the drawing of deeper, often naturally contaminated water into production wells. Deeper groundwater in the southern San Joaquin Valley tends to have elevated arsenic and uranium concentrations.
The Sustainable Groundwater Management Act (SGMA) requires the Kern County Sub-basin to achieve sustainability by 2040. The Groundwater Sustainability Plans developed by local agencies call for demand reduction, managed aquifer recharge, and significant fallowing of agricultural land. The implications for Bakersfield are enormous — less agricultural pumping could stabilize the aquifer but also means economic disruption in a region that depends on farming.
Chromium-6 and Arsenic: Natural and Industrial
Bakersfield-area groundwater contains naturally occurring chromium-6 (hexavalent chromium) and arsenic at levels that concern health advocates even when they fall below current federal MCLs. California had proposed a state MCL for chromium-6 of 10 ppb in 2014, withdrew it after legal challenges, and has been working on a revised standard.
The federal arsenic MCL of 10 ppb is met by Bakersfield’s municipal systems, but some private wells and small community systems in the area exceed it. Arsenic in Kern County groundwater is primarily natural — derived from the mineral composition of the aquifer sediments — but can be concentrated by over-pumping and drought conditions.
What Bakersfield Residents Can Do
Bakersfield’s municipal water meets federal standards, but the concentration of contamination sources in the region warrants active engagement:
- Review your CCR — know which contaminants are detected in your water and at what levels.
- Private well owners: comprehensive testing is essential — test for nitrate, DBCP, 1,2,3-TCP, arsenic, chromium-6, and uranium at minimum. Annual testing is recommended.
- Point-of-entry or point-of-use treatment — reverse osmosis removes the full spectrum of Central Valley contaminants. GAC systems address 1,2,3-TCP and DBCP specifically.
- Watch SGMA implementation — groundwater sustainability decisions will affect water quality, availability, and cost for decades.
- Stay informed on oil field injection — CalGEM’s Underground Injection Control program database tracks active and recently closed injection wells near your area.
If you’re concerned about your water quality, a certified water treatment professional can help you test your water and recommend the right solution for your home.