Application of a Three-Dimensional Model to Assess Seawater Intrusion in the South San Diego Embayment

Huntley, David; ,

Application of a Three-Dimensional Model to Assess Seawater Intrusion in the South San Diego Embayment

by David Huntley,

Document Type: Proceeding Paper

Part of: North American Water and Environment Congress & Destructive Water

Abstract:

The San Diego Formation is a Pliocene through Quaternary age aquifer occupying the southwestern-most part of San Diego County. Though the formation is widespread, thicknesses of up to 800 m (2600 ft) exist only in the South San Diego Embayment, bounded on the east by the La Nacion and Sweetwater faults, on the south by the U.S./Mexico border, on the west by San Diego Bay and the Pacific Ocean, and on the north approximately by Mission Valley and the San Diego River. The aquifer is vertically and laterally heterogeneous, with measured hydraulic conductivities in screened, permeable intervals ranging from less than 0.3 rn/day (1 ft/day) to 75 m/day (250 ft/day), and averaging 12 m/day (40 ft/day). These large variations occur over 1.5 m (5 ft) intervals. This variation markedly affects the predicted performance of season aquifer storage and recovery (ASR) systems and the rates and distribution of seawater intrusion under periods of prolonged pumped. DSTRAM (Huyakorn et al, 1994) a finite element, three-dimensional, density-dependent, solute transport code was used to simulate seawater intrusion. Simulations utilized both vertically homogeneous and heterogeneous permeability distributions and demonstrate the importance of defining small-scale permeability variations on the analysis of seawater intrusion.

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