OCWD basin storage increase could trigger higher pumping limits next year
Orange County Water District, California · Meeting date: September 9, 2026 · Published: September 10, 2026
Above-average rainfall and optimized stormwater capture at Prado Dam added 21,000 acre-feet to Orange County's groundwater basin storage in water year 2025-26. With the basin's overdraft now sitting comfortably within its target range, utility staff indicated that a wet winter could lead to a recommendation to increase the basin production percentage.
Key points
- Basin storage increased by 21,000 acre-feet, bringing the accumulated overdraft to 162,000 acre-feet, well within the target range of 150,000 to 200,000 acre-feet.
- The district captured 168,600 acre-feet of Santa Ana River base and storm flow, aided by 16.1 inches of rainfall and Forecast-Informed Reservoir Operations (FIRO) at Prado Dam.
- Groundwater Replenishment System (GWRS) recharge was 15,800 acre-feet lower than budgeted due to maintenance and product water pump refurbishments.
- Staff noted that if the upcoming winter is wet, they may recommend increasing the basin production percentage to allow producers to pump more groundwater.
Full report
The Orange County Water District (OCWD) recorded a 21,000 acre-foot increase in groundwater basin storage for the 2025-26 water year, placing the basin's accumulated overdraft at 162,000 acre-feet.
The positive storage update, presented at the September 9 Water Issues Committee meeting, keeps the basin squarely within the district’s target overdraft range of 150,000 to 200,000 acre-feet. According to staff, the favorable conditions could lead to operational shifts if the wet trend continues.
"The groundwater basin storage levels are really getting up there," a staff member noted during the meeting. "If we're sitting here next January and February and it is a wet winter, staff could recommend increasing the basin production percentage next year."
The storage gains were largely driven by above-average rainfall and optimized stormwater capture. The district recorded 16.1 inches of rain at its field headquarters, roughly 20% above the historical average. This contributed to 168,600 acre-feet of Santa Ana River base and storm flow recharge—22,600 acre-feet more than originally budgeted.
Staff attributed the successful stormwater capture to favorably distributed rainfall events and the implementation of Forecast-Informed Reservoir Operations (FIRO) at Prado Dam. The FIRO program, conducted in cooperation with the Army Corps of Engineers, allowed the district to hold a higher conservation pool elevation of 508 feet. Staff noted that only an estimated 2,000 to 3,000 acre-feet of water was lost to the ocean during the water year.
While river recharge exceeded expectations, recharge from the Groundwater Replenishment System (GWRS) fell 15,800 acre-feet short of the budgeted amount. Staff explained that the shortfall was due to reduced influent during maintenance by the Orange County Sanitation District, as well as periods of reduced GWRS production while OCWD refurbished product water pumps. Additionally, high groundwater levels in the forebay and at the Talbert Barrier limited injection and percolation rates during the winter.
In other business, the committee approved a $6.7 million construction contract to Big Ben Inc. for the Fullerton Well 10 PFAS Treatment Project. During the meeting, staff clarified that the project's higher-than-average cost is due to extensive pipeline work required to convey raw water from Well 10 to the Kim 2 well site for consolidated treatment, rather than building a standalone treatment facility at Well 10.
This summary was generated by AI based on the source document and may contain errors.
Source: Water Issues Committee Meeting, Orange County Water District