Operation of the Freeman Diversion, located on the Santa Clara River in Southern California, requires a challenging balance of fisheries, withdrawal, and sediment management. Freeman redirects water to recharge the aquifer underlying the Oxnard Plain, combating saltwater intrusion associated with agricultural and municipal withdrawals. The Santa Clara River has a flashy hydrologic regime, carries a heavy sediment load, and contains anadromous Southern California steelhead. Dam operations must provide sufficient flows for fish passage and aquifer recharge, while also flushing the forebay of sediment. As part of ongoing redesign, the authors have developed a two-dimensional mobile bed model of the Santa Clara River reach immediately upstream of the dam using SRH-2D software. The numerical model is being used in concert with reduced-scale laboratory model studies to evaluate the ability of proposed design alternatives to effectively flush sediment while meeting fish passage and aquifer recharge requirements and to inform future operations and maintenance.
