Chino Basin faces historic safe yield reduction to 117,500 acre-feet

Chino Basin faces historic safe yield reduction to 117,500 acre-feetThe Chino Basin Watermaster anticipates the largest safe yield decrease in its history due to climate and regulatory pressures, with a final reevaluation report expected in May 2026.

Initial technical results project the basin's safe yield will drop from 131,000 to 117,500 acre-feet per year.

The reduction is driven by climate conditions, state conservation regulations, and the need to prevent land subsidence.

A final Safe Yield Reevaluation Report is scheduled for completion in May 2026 following an October 2025 peer review.

IEUA continues to offset supply pressures through local capture, recording 11,450 acre-feet of stormwater and 11,552 acre-feet of recycled water year-to-date.

The Chino Basin is bracing for the largest safe yield decrease in its history, with preliminary projections indicating a drop from 131,000 to 117,500 acre-feet per year. Todd Corbin, General Manager of the Chino Basin Watermaster, presented the mid-cycle reevaluation update to the Inland Empire Utilities Agency (IEUA) board on March 4, 2026. The safe yield—defined as the amount of groundwater that can be safely extracted without causing undesirable results like land subsidence or water quality decline—is undergoing a critical adjustment to account for evolving regional conditions. Corbin noted that the basin's safe yield was originally set at 140,000 acre-feet in 1978. It was subsequently reduced by 5,000 acre-feet for the 2010 period, and dropped further to 131,000 acre-feet for the 2020 to 2030 cycle. The current projected decrease to 117,500 acre-feet reflects prospective estimates of future water budgets, driven by changing climate and precipitation patterns, shifting development, and new state conservation regulations. Following an independent peer review of the initial technical results published in October 2025, the Watermaster is finalizing its technical work through April. The final Safe Yield Reevaluation Report is expected to be completed in May 2026, at which point the Watermaster board will consider subsequent policy actions. To mitigate groundwater depletion and manage the basin's complex hydrology, IEUA continues to partner with the Watermaster on the Optimum Basin Management Program. The strategy encompasses 1,100 monitoring wells, extensive recharge operations, and a dry-year yield storage and recovery program with the Metropolitan Water District. Highlighting the agency's ongoing reliance on local supply optimization, staff reported during the meeting that IEUA has successfully captured 11,450 acre-feet of stormwater and 11,552 acre-feet of recycled water in the current fiscal year to date.