Ojai Basin groundwater quality remains stable in 5-year GSP evaluation

Ojai Basin groundwater quality remains stable in 5-year GSP evaluationA recent analysis of seven constituents of concern in the Ojai Basin reveals stable or decreasing concentrations across most wells, though isolated increases in nitrate and total dissolved solids will require ongoing monitoring.

Consulting firm Dudek presented a 5-year evaluation of water quality data (2021-2025) for the basin's Groundwater Sustainability Plan.

Of 23 sampled wells, only three exceeded the secondary maximum contaminant level (MCL) of 1,000 mg/L for total dissolved solids (TDS).

A trend analysis of 21 wells showed only five with increasing constituent trends, though all remained well below regulatory limits.

The agency is preparing to impose fines and penalties on well owners who are delinquent in submitting their extraction statements.

Groundwater quality in the Ojai Basin has remained largely stable over the past five years, according to a periodic evaluation of the basin's Groundwater Sustainability Plan (GSP) presented to the Ojai Basin Groundwater Management Authority (OBGMA) on June 25, 2026. A representative from consulting firm Dudek detailed the results of the water quality analysis, which compared data collected between 2021 and 2025 against the 2010 to 2020 baseline established in the original GSP. The analysis tracked seven constituents of potential concern: total dissolved solids (TDS), sulfate, chloride, boron, nitrate, iron, and manganese. Overall, constituent concentrations were stable or decreasing across the majority of the basin's wells. Of the 23 wells sampled for TDS, concentrations decreased in 16 wells and increased in five, with only three wells exceeding the secondary maximum contaminant level (MCL) of 1,000 milligrams per liter (mg/L). Similarly, nitrate levels decreased in 11 wells and increased in 10, with the maximum increase measuring approximately 1.5 mg/L. Only one well in the eastern portion of the basin exceeded the primary MCL of 10 mg/L for nitrate. Manganese remains naturally elevated across the basin, with eight wells testing above the secondary MCL of 0.05 mg/L. Dudek also performed a Mann-Kendall trend analysis on 21 wells with sufficient historical data. Only five wells showed an increasing trend for constituents—two for chloride, two for nitrate, and one for sulfate. However, the consultant noted that the measured concentrations at these specific wells are currently at or below half of their respective MCLs, indicating that the increases do not pose an immediate regulatory concern. Dudek is currently evaluating correlations between the water quality data and other variables, such as precipitation, groundwater extraction, and well depth, to finalize the 5-year evaluation report. In separate administrative action, OBGMA is escalating enforcement against well owners who have failed to submit required extraction statements. General Manager Julia Aranda reported that the agency is "chipping away" at delinquent accounts and has recently issued notices to three well owners. If the issues are not resolved, the board may impose fines and penalties at its July meeting. Meanwhile, negotiations regarding the Ventura River Watershed Adjudication are progressing. Chair Richard Hajas noted that while local parties—including the City of Ventura, Casitas Municipal Water District, and the City of Ojai—are "very close" to an agreement, significant issues remain unresolved with the state. A hearing on the adjudication proceedings has been rescheduled for July 1.