Numerical modeling was used to examine the character of aquifer systems in alluvial basins in south-central Arizona. The report documents the modeling approach, design and calibration procedures, and results of simulations made by using specific and general models. Transferability of geohydrologic information among basins was tested and generally proved successful. Extensive sensitivity testing was done on all models. Sensitivity to specific properties is related to geologic environment and the magnitude of predevelopment flow quantities.