Kern Subbasin earns a break

This time last year, there was a lot of concern to be had in Kern County. The Department of Water Resources (“DWR”) had reviewed the Groundwater Sustainability Plans (“GSP”) prepared by Kern Subbasin Groundwater Sustainability Agencies (“GSA”) and referred them to the State Water Resources Control Board (“State Board”) for potential probationary action. The Tule Subbasin was then placed on probation, and the tone from the State Board was not positive. Farmers and water agencies were concerned that probation would mean increased costs and a breakdown of trust between locals and the state. Locals not directly tied to agriculture were also unsure what this all meant for them, particularly when Kern has several areas with water quality problems. In February of this year, things started to look a little better, as the State Board saw greater progress and issued a continuance rather than opting for probation. More work was needed, but positive change was already underway.

Last week, the State Board voted to return the Kern Subbasin back to DWR. The most recent plan represents a massive amount of coordination by over 20 different GSAs working to implement the Sustainable Groundwater Management Act (“SGMA”). The subbasin is also the largest in the state at approximately 1.8 million acres. The Tule, Kaweah, and Tulare Lake subbasins to the north could all fit within the Kern Subbasin. The scope of developing GSPs for such a large and diverse area presents numerous challenges, but the Kern subbasin team successfully addressed the concerns of the State Board. While the process of returning the basin to the DWR begins, it does not mean that there still isn’t work to be done or concerns. The issues of communication, water levels and quality, as well as subsidence, will be key in the work the subbasin has to do as it transitions back to DWR oversight.

Working Together

In 2020 and 2022, several different GSPs were submitted by the various GSAs. After reviewing each of these plans, they were deemed “inadequate”. In the initial review of the GSPs for the Kern Subbasin, DWR staff noted that one significant deficiency was that they were "fragmented and Byzantine" in their approach. The 2024 GSP went a long way to addressing that concern. One of the major changes between the 2022 GSPs and the 2024 GSP was that the basin became coordinated. Rather than many independent plans, the subbasin coordinated to develop a single plan, and GSAs that wanted to provide extra details about their areas were allowed to include Blue Pages, highlighting specific management actions or projects. In addition to the subbasin agencies developing better coordination, at the February 2025 meeting, the State Board sought to increase public outreach. The subbasin began hosting public events, conducting informational sessions both in person and online, and expanding its social media presence. This was all in addition to the monthly public meetings that each GSA regularly holds. One of the themes of the most recent hearing by the State Board was that both the coordination and public outreach events need to continue. SGMA and its implementation are complex issues that many in the community lack a thorough understanding of. State Board members emphasized the importance of improved communication between the GSAs and the community in the subbasin. This could help bridge the gap between GSA activities and community concerns, such as those related to groundwater quality.

Groundwater Levels and Quality

The 2025 GSP implemented a more uniform approach to methodology and setting groundwater levels. In the earlier plans, GSAs largely set Minimum Thresholds (“MT”), the lowest tolerable groundwater levels, or Measurable Objectives (“MO”), which are stable groundwater levels. These are important for several reasons. First, when groundwater falls below an MT, it could trigger an Undesirable Result (“UR”). Keeping groundwater levels above the MT and ideally working towards the MO is one of the broad goals of SGMA. The State Board was generally pleased with the Subbasin efforts, requesting changes in a limited number of monitoring wells.  The State Board was also keen to ensure that there were sufficient monitoring wells to not only track water levels, but also to monitor water quality. Several small water systems and cities in Kern Subbasin have ongoing water quality concerns ranging from nitrates to arsenic to 1,2,3-TCP. There is some nuance here because SGMA only applies to conditions that occur after the law was passed in 2015. Many of these water quality concerns predate SGMA, but the GSAs are accountable for any GSA-related actions that might contribute to URs relating to both groundwater levels and water quality concerns. Most of these are being well-managed, but if we were to experience another prolonged drought, water levels could fall, and we might see a greater need to avoid those URs around groundwater levels and water quality. In previous GSPs, groundwater levels were the main proxy for several other URs, but something like water quality or subsidence requires more factors, which is why they were given much additional attention in the new GSPs.

Managing Subsidence

Kern County also benefits from not having extreme subsidence issues, unlike those present in the Tule, Kaweah, or Tulare Lake subbasins. When examining even the most recent DWR report on the issue, it is evident that subsidence continues in those areas. Within Kern Subbasin, two areas along the aqueduct are of concern, and both of these also have oil and gas fields that are likely contributing to land subsidence. As SGMA is one of the few tools to address subsidence, more work will be needed to understand why subsidence is present in these areas. Along the northern area of concern, the Westside Water Authority GSA has instituted a pumping moratorium. The most significant areas of subsidence in Kern are mostly in the northern part of the subbasin, which borders the Tule and Tulare Lake subbasins. These two subbasins are facing probation. In Kern, there are other areas of subsidence concern that extend down into the Kern Friant canal or further south into the southern parts of the subbasin. As with groundwater levels and water quality concerns, subsidence will be a third area of concern being monitored; however, it is unlikely to be the issue in the Kern Subbasin that it is just to the north.

The Kern Subbasin GSA teams should be very proud of the work they have done in addressing the concerns of the State Board staff and board members. Board member Sean Maguire noted that, even a year ago, he would not have imagined that the Kern Subbasin would be in this position. The return to DWR is surely seen as a win, but we should not forget that GSP implementation is an ongoing process. Each year presents new hydrological conditions that require management to stay in line with SGMA. For now, GSAs in Kern will have a little time to breathe, implement plans and management actions, and hope that precipitation conditions remain normal or above average.