40 Years of Salt Management in the Orange County, California Groundwater Basin

This presentation discusses achievements and challenges with managing salt concentration in the Orange County Groundwater Basin, located in coastal southern California.  Source water for managed aquifer recharge of the groundwater basin includes Santa Ana River flows and recycled water.  The primary mechanism to remove salt from the basin is groundwater pumping.  Over the last 40 years, the salt concentration has been managed through: (1) improvements in the quality of water discharged to the Santa Ana River by treatment agencies in the upper Santa Ana River Watershed, (2) wetlands treatment of Santa Ana River water, (3) groundwater desalters, and (4) recharge of low salt concentration recycled water.  The quality of water discharged by treatment agencies is regulated by the State of California pursuant to the Porter Cologne Water Quality Control Act and the federal Clean Water Act.  Improvements in the quality of water discharged to the Santa Ana River, for example, in nitrate concentration, have helped protect groundwater quality in the Orange County Groundwater Basin because the Santa Ana River is the primary source of water used to replenish the basin.  The Orange County Water District has funded treatment wetlands and groundwater desalters in cooperation with local stakeholders to improve water quality.  The production of recycled water through reverse osmosis treatment has provided water with a total dissolved solids concentration of approximately 50 milligrams per liter.  Recharge of this recycled water provides a significant salt concentration benefit to the groundwater basin.  The primary challenges associated with these efforts regard the cost and time period required for implementation.  These challenges include who pays for the project, funding availability, and regulatory issues that extend the time required to plan and implement projects.