• San Bernardino Valley Water Conservation District

*A Century of Stewardship: Modeling the Effects of Managed Recharge on the San Bernardino Basin Aquifer from 1912–2023* examines the long-term benefits of managed aquifer recharge conducted by the San Bernardino Valley Water Conservation District. Prepared by GEOSCIENCE Support Services, Inc. in June 2025, this technical memorandum draws on 112 years of operational records to evaluate how diversions from the Santa Ana River and Mill Creek have influenced groundwater storage, groundwater levels, and regional water supply reliability.

The study uses the updated Integrated Santa Ana River Model, which combines watershed and groundwater modeling, to compare historical conditions with a scenario excluding the District’s local surface water diversions for recharge. Between 1912 and 2023, the District diverted and recharged more than 1.7 million acre-feet of local surface water. Compared with the scenario without these operations, modeling indicates an average annual groundwater storage benefit of approximately 7,570 acre-feet. By December 2023, modeled groundwater levels were more than 25 feet higher across approximately 75 square miles of the basin. The analysis also estimates that 188 production wells would have been partially or fully dewatered without the District’s recharge activities.

The report documents model updates, historical water budgets, groundwater-level comparisons, and benefits extending to neighboring groundwater basins and riparian vegetation. It also discusses model limitations and uncertainty associated with estimated hydrologic inputs and pumping records.

For water managers, recharge practitioners, and planners, this case study illustrates the cumulative value of sustained local surface water capture, gravity-fed recharge basins, and long-term monitoring. It offers a practical example of how historical operational data and integrated modeling can help quantify recharge benefits and inform groundwater sustainability planning.

• Land Use Planning and Management
• People and Water
• Recharge and Extraction Methods and Measurement