Orange County Water Agencies Prevail in Major Groundwater Rights Case, Safeguarding Water Equality for 2.5 Million Residents

Costa Mesa, Calif. – July 9, 2025 — In a major victory for water justice and regional collaboration, several Orange County water agencies, including Mesa Water District (Mesa Water®), have successfully concluded a multiyear legal dispute that ensures the continued protection of the Orange County Groundwater Basin (Basin) — the primary source of drinking water for 2.5 million residents.

Five Orange County water departments and special districts joined forces as cross-complainants in the case of Irvine Ranch Water District (IRWD) v. Orange County Water District (OCWD). Mesa Water and fellow cross-complainants have now received payments from IRWD to cover litigation costs. These agencies united to defend the public’s access to a vital water supply and to prevent legal maneuvers that could have unfairly shifted costs and water rights in IRWD’s favor. A summary of the multi-phase litigation and outcomes is posted at www.mesawater.org/about-us/orange-county-groundwater-basin/orange-county-water-district-ocwd-prevails-irvine-ranch.

“This is more than a legal win — it’s a win for every family, business, and community that depends on this local water supply,” said Marice H. DePasquale, Board President of Mesa Water. “The Court of Appeal’s decision affirms the principles of fair and transparent groundwater management and reflects our commitment to protecting ratepayers from unnecessary and unfair costs.”

The case, filed by IRWD in 2015, sought changes to the longstanding management of the Basin. Had it succeeded, the lawsuit would have allowed IRWD to extract more water from the Basin while paying less than the other 18 Groundwater Producers, disrupting long-standing cooperative management of the Basin and potentially increasing costs for millions of customers.

Instead, the courts sided with OCWD on 16 of 17 claims — a resounding affirmation of the OCWD’s stewardship of the Basin. The decision, upheld in October 2024 by the California Court of Appeal, ensures that the Basin continues to be managed fairly for the benefit of all.