Post-Optimization Scenarios for the Santa Barbara Groundwater Model, California

The city of Santa Barbara, in cooperation with the U.S. Geological Survey (USGS) California Water Science Center, developed a three-dimensional density-dependent groundwater-flow and solute-transport model (the Santa Barbara Flow and Transport Model; Paulinski and others, 2018; Nishikawa and others, 2018). The Santa Barbara Flow and Transport Model met the objectives of estimating the sustainability of Santa Barbara's groundwater basins by optimizing the total capacity for pumping while limiting drawdown and seawater intrusion.

In conjunction with the 2020 Enhanced Urban Water Management Plan, the city of Santa Barbara sought to evaluate the groundwater flow model sustainable use as defined by minimizing changes in storage. Because change in storage was not optimized as an objective for the Santa Barbara Flow and Transport Model, post-optimization assessment is required to effectively evaluate the pumping capacity and aquifer recovery in the basin. To accomplish this, the completed Santa Barbara Flow and Transport Model was coupled with a management optimization tool, in this case a multi-objective evolutionary algorithm, to determine optimal pumping strategies that maximize the water production and at the same time satisfy user-defined storage, drawdown, and chloride-concentration constraints.