Managing Salinity in the Upper Santa Clara River System of California

The Santa Clara River in Southern California provides beneficial uses that include agricultural water supply, groundwater recharge, and rare and endangered species habitat. Significant urbanization has contributed to elevated chloride concentrations along portions of the river in the Santa Clarita Valley and downstream areas. The affected reaches of the Santa Clara River are included on California's list of impaired waters with respect to chloride. A total maximum daily load for chloride, which was originally adopted by the Los Angeles Regional Water Quality Control Board in 2002 and later amended in 2004 and 2006, required special studies to provide the technical basis for establishing appropriate chloride water quality objectives. As part of these studies, a fully integrated groundwater/surface-water numerical model was developed to facilitate the implementation of the chloride total maximum daily load. Modeling results indicated that implementation of expensive water treatment alternatives at two water reclamation plants would not likely lead to consistent compliance with existing chloride objectives in local streams or underlying groundwater basins. Accordingly, the model was used to develop a cooperative alternative water resources management approach. Once implemented, this approach could protect beneficial uses, aid in managing salinity (specifically chloride concentrations) in the Santa Clara River system, improve salt exportation from the study area, and provide enhanced water-supply benefits to water users in affected areas, while providing flexibility and more feasible chloride compliance solutions.