Orange County Water Districts Managed Aquifer Recharge System: Where It Has Been and Where It Is Going…

Since Orange County Water District (OCWD) began purchasing land for recharge in the Santa Ana River (SAR) channel in 1936, it has developed a large managed aquifer recharge (MAR) system that now covers over 1,500 acres and recharges an average of 230,000 acre-feet per year of water to the groundwater basin.  This MAR system has effectively doubled the yield of the groundwater basin and provides an average of 75 percent of the groundwater pumped from the basin every year. 

 Over the last 30 years there has been a transition in the recharge water source from imported supplies to locally derived supplies, primarily due to increased discharges to the SAR from upstream development.  Although the local supplies are not purchased, there is a cost associated with this water due to higher solids loading to the MAR system, which results in more rapid clogging of the MAR facilities.  Due to the high cost of land in the recharge area of the basin, it is becoming more important that OCWD find alternative methods to increase MAR system capacity.  Methods currently being explored include treating SAR flows to remove the suspended solids before they reach the recharge basins, thereby maintaining higher sustainable recharge rates and testing of subsurface recharge galleries that would be able to recharge water under parking lots and other public areas.  Research conducted by OCWD show that much of the clogging is caused by suspended particles less than 1 micron in diameter, which poses challenges to conventional treatment methods being tested.