Groundwater plays a vital role in California’s water supply, accounting for a significant portion of the Central Valley’s annual water budget and even more so in dry years. However, prolonged drought conditions and persistent aquifer overdraft have led to steady declines in groundwater levels over the past two decades. The 2014 passage of the Sustainable Groundwater Management Act marked a turning point, mandating sustainable groundwater management and allowing state intervention where necessary. Since then, six basins have come under state oversight, with one more added this year.
At Tuesday’s meeting, the State Water Board provided an update on its intervention efforts and the current status of these basins. The update was given by Brianna St. Pierre, Assistant Director for the State Water Board’s Office of Sustainable Groundwater Management; Amanda Howrey, engineering geologist; and Eric Holmes, analyst. Deputy Director of DWR for Sustainable Groundwater Management, Paul Gosselin joined the panel to discuss the Department’s efforts to support SGMA implementation, periodic evaluations, and the development of a BMP and a regulation to address land subsidence.
SGMA BASICS
To address or avoid the overconsumption of groundwater in medium-high and critically overdrafted subbasins, SGMA requires groundwater sustainability agencies or GSAs to create groundwater sustainability plans (GSPs) that clearly define the groundwater issues in the subbasin and strategies to correct them; submit annual reports that demonstrate progress towards achieving sustainability goals; and to periodically evaluate and update GSPs. The plans are to achieve sustainability within 20 years.
SGMA defines sustainability as operating a groundwater basin within its sustainable yield without causing undesirable results. Undesirable results are defined as significant and unreasonable occurrences of six indicators caused by groundwater conditions:
- Groundwater level declines
- Storage reduction
- Seawater intrusion
- Degraded water quality
- Land Subsidence
- Surface water Depletions
The GSAs define what is significant and unreasonable in their GSPs.
THE STATE WATER BOARD’S INTERVENTION PROCESS
The flow chart outlines the process for GSP review under SGMA. The responsibility of SGMA implementation oversight is divided between the Department of Water Resources (DWR) and the State Water Board. DWR conducts initial and periodic evaluations of GSPs and manages GSP and GSA information. Once a GSP is adopted, DWR has two years to evaluate it. If the plan is approved, GSAs implement the plan and submit annual reports to DWR. If DWR determines the plan to be inadequate to achieve sustainability, the State Water Board’s role under SGMA is triggered.
The discretionary steps the Board can take are shown below. The State Water Board reviews the inadequate subbasin GSPs and determines if a probationary designation is necessary. Board staff prepare a report summarizing and recommending potential actions to remedy the identified deficiencies. If deficiencies are not corrected, the Board may hold a probationary hearing to determine if probation is warranted for the subbasin.
If the Board adopts a probationary determination, the GSA will have one year to correct the identified deficiencies. The Board may require meters and groundwater extractors to report their groundwater extractions to the Board and pay fees based on the amount they pump. If the deficiencies are not corrected after one year on probation, the Board may choose to develop an interim plan to manage groundwater temporarily. The Board would provide an opportunity for public input on the draft interim plan and hold a public hearing to consider adopting the interim plan.
The Board will only intervene when local efforts fail. State intervention temporarily protects the basin until the GSA can resume control, but it is not meant to replace local management under a GSP. State intervention ends when the State Water Board determines that GSAs have corrected deficiencies.
UPDATE ON THE SEVEN BASINS SUBJECT TO STATE INTERVENTION
This map shows the status of seven basins subject to state intervention by the State Water Board. On March 2, 2023, DWR determined that the revised GSPs for six critically overdrafted groundwater basins were inadequate: Tulare Lake, Tule, Kern County, Kaweah, Chowchilla, and Delta Mendota.
More recently, in February 2025, DWR determined that the Pleasant Valley subbasin in Fresno County has an inadequate GSP. The subbasin followed the others by about two years because there is a difference of two years for SGMA implementation for non-critically over-drafted subbasins. (Pleasant Valley is not discussed in the remainder of this presentation because that basin only recently came under the Water Board’s purview.)
Board staff evaluated more than 84 GSPs in the last two years for the six basins DWR initially referred to the Water Board. The GSPs reviewed had similar deficiencies in addressing groundwater level decline, groundwater storage reduction, and land subsidence.
Staff gave updates on the six subbasins:
- Tulare Lake: On April 16, 2024, the Board put the Tulare Lake subbasin under probation. All actions related to the Tulare Lake probationary designation are currently suspended due to ongoing litigation.
- Tule: On September 17, 2024, the Board put the Tule Subbasin under probation. Over the last year, staff has met with GSAs to discuss fixing deficiencies and review the five new GSAs and three new GSPs. Non-exempt extractors began measuring extractions on January 1, 2025. Staff are looking into tracking the implementation of GSA management actions. Planning has already started on an effort to support extractors with submitting their first reports, which are due February 1, 2026.
- Delta Mendota: The adopted 2024 Delta Mendota GSP shows significant progress toward sustainability and coordination. Staff continues to coordinate with the GSAs regarding the remaining concerns identified in the updated GSP. Staff expects to produce a recommendation to the Board in late 2025.
- Chowchilla: The recently updated 2025 Chowchilla GSP shows significant progress towards protecting drinking water users and slowing subsidence. Staff continues coordinating with the GSAs, and a recommendation to the Board will likely be released this spring.
- Kern: The Board is set to continue the Kern County probationary hearing on September 17, 2025. Staff is reviewing GSA outreach and engagement plans, proposals for GSA monitoring networks, and well mitigation plans for groundwater quality and levels. A revised GSP is due to board staff on June 20, 2025
- Kaweah: The Kaweah probationary hearing originally set for January 7, 2025, was canceled. Staff are reviewing the amended 2024 GSPs, which show significant progress towards sustainability. A potential board action is anticipated this summer.
The six basins are all managed by multiple groundwater sustainability agencies and, in many cases, under multiple groundwater sustainability plans, which adds complexity when developing basin-wide descriptions of water budgets and sustainability goals.
Across all six basins, agriculture remains the predominant use of groundwater. The long-term shift from planting annual crops, which can be fallowed during dry years, to permanent tree crops has significantly reduced the flexibility of these basins to adjust water use in response to drought conditions, making groundwater when surface water is limited.
A relatively small number of landowners make up most of the irrigated land in the six basins; the basins are also home to many smaller farmers. While larger growers have more resources to adapt to changing conditions and increased fees, smaller growers may have more trouble keeping up with decision-making processes and new requirements.
SUCCESS STORIES
Kern County: Addressing CA Aqueduct Subsidence
In the Kern subbasin, the West Side District Water Authority GSA contains a portion of the California Aqueduct, which has historically been impacted by subsidence. Both groundwater and other factors, such as oil and gas extraction, likely drive the subsidence.
The GSA has implemented several features to minimize future subsidence. All wells within the GSA must be registered and equipped with a flow meter. De minimis wells are excluded from metering requirements.
The GSA established a monitoring corridor that extends two and a half miles from either side of the California Aqueduct in which no new wells are allowed, except replacement wells and de minimis wells. Most extractions are prohibited, and the allowed extractions must be reported to the GSA. The GSA also commits to continue working with the California Aqueduct subsidence program and other beneficial users to minimize the impacts to the aqueduct.
Chowchilla: Addressing land subsidence
In the Chowchilla subbasin, Triangle T Water District has taken actions to address lower aquifer pumping in western Chowchilla, which has caused subsidence impacts to infrastructure within the adjacent Delta-Mendota subbasin.
These actions include the Triangle T Water District GSA landowners forming an agreement for roughly 14,000 acre-feet per year with surface water purveyors and Delta-Mendota to stop subsidence impacts, encourage recharge, and allow a transition to upper aquifer pumping for irrigation demand. Triangle T Water District, GSA, landowners agreed to limit lower aquifer pumping to an estimated safe yield of half an acre-foot per acre.
Kaweah: Domestic well mitigation program
In developing the Kaweah subbasin’s well impact mitigation programs, the GSAs hosted multiple public meetings to receive feedback on the mitigation program, developed an alert system to notify well users of potential impacts, and are providing communications in various languages.
The program includes a $5.8 million annual budget fully funded by the GSAs for drinking water well impacts, groundwater quality impacts, and critical infrastructure impacts due to groundwater pumping and management. This well mitigation is implemented in partnership with Self Help Enterprises. Commitments include 24-hour emergency bottled water service, and 72-hour tanked water service if a domestic well is impacted.
The programs consider both short-term water supply needs and options for longer-term solutions, including deepening wells, drilling a new well, or connecting households to nearby water systems.
NEW LAND SUBSIDENCE BMP AND REGULATION COMING
Paul Gosselin, Deputy Director at DWR for Sustainable Groundwater Management, noted that the two drivers that caused SGMA to be enacted in 2014 were high subsidence rates and thousands of wells that went dry during the drought exacerbated by poor groundwater management. He said it was surprising that those were not seriously addressed in the initial plans.
Land subsidence is a major issue, affecting not just canals but also roads, gas lines, and other infrastructure. “A lot of this isn’t even apparent to the infrastructure owners; it’s just buried in O&M repairs,” said Mr. Gosselin. “It’s becoming apparent in some areas that this is just the way things are, and it’s just a cycle of state, federal, and local public dollars cycling back to mitigate something that’s continually not being addressed. So the time is now. We will be issuing best management practice document and likely regulations to accompany that in the second quarter of this year.”
There will be ample opportunity for public comment as documents will be circulated for review, and the legislation requires at least three workshops and a presentation to the California Water Commission.
To stop subsidence, groundwater levels need to be brought back up to the point when groundwater levels are high enough to stop subsidence; in some places, that may be 50-100 feet. “Whether it’s practical or impossible, it’s going to be very difficult, but we need to start that process now,” Mr. Gosselin said. “It’s going to cause a significant ask on land transition. So there will have to be a considerable state effort in these areas because you are dealing with a lot of ag transition, jobs, and community impacts, but we’re also dealing with a very serious problem that is affecting infrastructure, wells, and water conveyance.”
Vice Chair De De D’Adamo noted that SGMA specifically says GSAs are not responsible for impacts from before 2015, so how will subsidence regulations fit in with the requirements enacted by the legislature?
Mr. Gosselin said there are not going to be new requirements; it will be clarifying the intent of SGMA. He noted the language for subsidence was different then the other indicators: it said the intent of SGMA is to minimize or avoid subsidence.
“That is different than any of the other indicators; it gave a clear directive about subsidence,” he said.
The way the law is written, the GSAs are responsible for identifying undesirable results. The Department feels it would be a step over the line for DWR to state what those undesirable results are, or even what the critical infrastructures are.
“This is why comments are very helpful for us,” he said. “We’ve had entities write into us, and in this case, owners of infrastructure, whether it’s levees or conveyance, and they’ll say, you’re going to let this subside X number of feet, and with our freeboard, that’s not going to work. So we’ll pose the question: can you justify that not being undesirable when the owner of the infrastructure says that? Explain that to us.“
The same thing was done with drinking water. “There’s no way we could mandate a GSA to mitigate wells. The law does not give us the authority to do that. So the way it was done was, you’re going to let wells go dry; explain to us how that’s not an undesirable result.”
DWR’S FOCUS MOVES TO PERIODIC EVALUATIONS
DWR will continue to review plans as necessary, but will be shifting more of the emphasis on whether basin conditions are improving, project management actions are actually being implemented, and recommended corrective actions are being carried out. “The periodic evaluation and annual reports provide a means for us to evaluate progress, real progress on the ground, empirical progress, not what’s written on paper or what a model may show,“ said Mr. Gosselin.
If the Department starts to see significant problems, such as basins not improving, or out of compliance, then the Department may deem a basin inadequate and send it back to the Board, even the basins that were initially approved.
“We will be looking at their interim milestones, whether they are on track and in a real-world basis on what the data shows, projects and management actions proceeding, and if the plans are amended or revised, we’ll be looking to see if those changes are in compliance, and if they made the changes to our recommended corrective actions,“ he said. “In the end, all plans will adapt and change.”
As implementation continues, land repurposing will continue to be a challenge, so the Multibenefit Land Repurposing Program and other programs will be critical. “Whether that’s half a million acres of ag or a million, what can be done to achieve sustainability but lessen the economic impacts is really a moral obligation. We have to try to do what we can to achieve the goal, but help communities through this transition.”
SAFER FUNDING
Board member Laurel Firestone noted that the Board’s SAFER funding and public funding has been and continues to be used to mitigate drinking water impacts, including hauled water for domestic wells. “It continues to be a strain on the limited funding we have for ensuring all Californians can have access to safe and affordable drinking water. So I’m excited for these mitigation programs in the critically overdrafted basins, in particular, where a lot of wells continue to rely on hauled water and use public financing for impacts after 2015. … I’m hopeful that through this process of periodic review, it’s an opportunity to make sure that those mitigation programs in those areas can start to take that on.”
