RIDGECREST, Calif. (July 10, 2026) — After taking evidence and hearing several days of testimony from expert hydrogeologists and groundwater modelers, the Indian Wells Valley Groundwater Basin Adjudication Court has concluded that it will appoint an independent groundwater expert, called a Special Master, to assist the Court in the review of the complex scientific evidence. Initially, the Court sided with the Indian Wells Valley Water District, Searles Valley Mineral, and Meadowbrook Dairies (Large Pumpers) opposition to the appointment of an independent expert to assist the Court. However, after some pointed questioning of experts for the Large Pumpers and expert testimony showing fatal flaws in the Larger Pumpers analysis, the Court concluded that an independent expert review assistant was necessary to ensure the Court’s decision is based on a thorough evaluation of the scientific evidence.
During this Phase, the Court is tasked with the incredibly important duty of determining the Indian Wells Valley Groundwater Basin’s (Basin) “safe yield.” While there are some nuanced differences, safe yield is the functional equivalent of what the Sustainable Groundwater Management Act (SGMA) calls “sustainable yield” and both generally refer to the volume of water that can be withdrawn from the Basin each year without causing harms, such as worsening water quality and the loss of wells due to declining groundwater levels. Importantly, these yields cannot exceed the Basin’s historical average annual recharge—the amount of water that naturally replenishes the groundwater supply each year—but these yields will be lower if the Court’s determination accounts for water that is naturally used by plants and other environmental processes, a process known as evapotranspiration.
Experts for the United States Navy’s used two sophisticated 3-D groundwater models to estimate that the Basin’s safe yield is 7,650 acre-feet per year (AFY). The Indian Wells Valley Groundwater Authority adopted this estimate for use in its 2020 Groundwater Sustainability Plan (GSP) which the California Department of Water Resources approved and found to be based on the best available science. During the trial, independent experts for the Navy and the Authority both testified in support of the 7,650 AFY estimate, while the Large Pumpers advanced several higher safe yield estimates. A hydrogeologist for the Water District presented an estimate as high as 18,200 AFY but the Large Pumpers principal trial estimates clustered around 14,300 to 15,400 AFY, which testimony revealed to be roughly 170% higher than the average estimate of 15 studies since 1989.
In the coming weeks, the parties will draft their closing trial briefs, and the Court will ask the California State Water Resources Control Board for a list of qualified experts to act as a Special Master.
An obvious focus of closing briefs will be several courtroom exchanges that drew considerable attention.
Early on, the Water District called Timothy Parker, a hydrogeologist who has worked for the Water District for nearly 15 years on groundwater supply issues. Parker was the lead coordinator of the Technical Working Group formed by the Large Pumpers to support their litigation efforts and his firm developed the Water District’s groundwater model that was in turn used by all the Large Pumpers. During cross-examination, questions arose regarding Mr. Parker’s groundwater modeling qualifications and after he acknowledged that he was not a modeler and could not fully explain certain empirical modeling techniques, Judge Claster struck Mr. Parker’s groundwater modeling testimony in its entirety.
Another notable moment occurred during the testimony of Dr. Matthew Tonkin – groundwater modeler hired to testify for the Large Pumpers after Mr. Parker’s firm had developed the Water District’s groundwater model. The Large Pumper’s safe yield calculation relies heavily on a ten-year period (2014 through 2023) that included two of the wettest years on record for the Basin. During cross-examination, Dr. Tonkin was handed a calculator and asked to perform the same safe yield calculation using a longer 25-year period. After completing the calculation, Dr. Tonkin acknowledged that the Large Pumpers estimated safe yield analysis dropped dramatically—from more than 14,000 AFY to roughly 8,000 AFY.
The impacts of the Large Pumpers base period selection resurfaced in their next witness hydrogeologist Eddy Teasdale. Mr. Teasdale testified that the historical period used by the Large Pumpers had been selected before the safe yield calculations were performed. However, during cross-examination, attorneys introduced an internal email in which Teasdale wrote to an attorney for the Large Pumpers, “We’ll see how this base period safe yield value compares with 2016 to 2021 and can share preliminary results with you next week.” When Teasdale testified that he did not compare different time periods before selecting the final base period, Judge Claster directly questioned the apparent inconsistency, asking, “So what does that word ‘compare’ mean in the e-mail, if not that?” The exchange highlighted the Court’s focus on how the Large Pumpers selected their base period and how that choice affected calculations that Dr. Tonkin testified could nearly double their safe yield estimate.
In another dramatic twist Mr. Teasdale’s testimony was further impeached when he was confronted with a prior comment letter wherein, he asserted that a groundwater model such as the one used by the Navy “would be the most robust tool to determine” safe yield. Mr. Teasdale also asserted that the Basin’s historic recharge estimates should be bookended at 4,100 – 7,700 acre feet per year.
The last witness to testify was the Navy’s expert Dr. Sean McKenna – an expert with nearly 40 years of experience in groundwater research and modeling who has authored approximately 100 peer-reviewed publications. Dr. McKenna testified that the Navy’s estimate of 7,650 acre feet per year was supported by two well calibrated 3-D groundwater models. In contrast, Dr. McKenna testified that the Water District’s Parker Model simulates a non-existent wet lake covering roughly 20 square miles. Dr. McKenna further testified that the non-existent wet lake was a fatal flaw in the Water District’s Parker Model, stating that it indicated the model was being manipulated by forcing physically impossible amounts of recharge into the Basin. This testimony was consistent with an earlier concession made during cross-examination by Dr. Tonkin, who acknowledged that the model simulated groundwater levels in the Rose Valley area more than 1,000 feet above the land surface. He agreed that, if those model results were accurate, drilling a well in that location would produce a 1,000-foot-high geyser—an outcome that illustrates the physically unrealistic nature of the model’s predictions.
In the coming weeks, the Court will appoint the Special Master and the Special Master’s review period will begin. Given the volume of evidence and the complexity of the scientific issues, the Special Master’s review is expected to take several months before the Court issues its long-awaited ruling—a decision that will play a critical role in shaping the future management of groundwater resources in the Indian Wells Valley.
“The trial is proceeding, and the evidence is before the court,” said Scott Hayman, chair of the Indian Wells Valley Groundwater Authority. “What we know for certain is that this basin is in critical overdraft and that time is not on our side. Our work to bring this basin into balance will continue in the courtroom and beyond it.”
About the Indian Wells Valley Groundwater Authority
The Indian Wells Valley Groundwater Authority (IWVGA) is the groundwater sustainability agency for the critically overdrafted Indian Wells Valley groundwater basin. The basin spans portions of Kern, Inyo, and San Bernardino Counties. It is home to the City of Ridgecrest and the U.S. Naval Air Weapons Station China Lake, a critical low-flight, weapons development, and testing facility. The groundwater basin serves approximately 38,000 residents.
IWVGA is a joint powers authority that includes representatives from Kern County, the City of Ridgecrest, Inyo County, San Bernardino County, and the Indian Wells Valley Water District. Two federal agencies, the United States Navy and the Bureau of Land Management, are also represented as ex-officio members of the IWVGA Board.
