This paper demonstrates the application of a groundwater quantity and quality model to large-scale groundwater basin management. The model employs a finite difference formulation of groundwater flow to compute the groundwater elevations at the node points of a two-dimensional homogeneous aquifer. A compatible groundwater quality model uses a control volume or mass balance approach to compute the concentration of a conservative constituent at each node. The model was calibrated to a 1200 mi2 groundwater basin in central California. Over 300 nodes were used in a symmetrical network. Water and waste water management alternatives are input to the model: amounts of pumping, natural infiltration, surface water use, and waste water recharge at selected future dates are specified. The impact of five alternatives on the groundwater basin over a simulated 45 years of operation is shown. Thus the evaluation of alternative water resource management schemes was based, in part, on model performance. This type of groundwater model shows promise as an integral tool in planning and managing the development of groundwater basins.