Use of a groundwater flow model to assess the location, extent, and hydrologic properties of faults in the Rialto-Colton Basin, California

Faults within a groundwater basin can greatly influence the direction of groundwater flow and contaminant migration. Existing steady-state and transient groundwater flow models were used to assess the location, extent, and hydrologic properties of two alternative fault configurations within the Rialto-Colton basin. Adjustments were made to the hydrologic properties of the faults and the location of the interface between the model cells that define the fault locations. The first configuration tested was the reorientation of Barrier H, a mapped fault that has been subject to various interpretations. The second configuration tested included the redefined Barrier H and a single composite of two previously unmapped faults. Steady-state and transient simulations for both alternative models produced good overall fits to the measured data and are similar to those of the existing model. However, the second alternative fault configuration better represents the available data.