MODELING SAFE AND SUSTAINABLE YIELDS FOR A GROUNDWATER BASIN UNDERGOING DEVELOPMENT

The rapid growth of human population is increasing the demand on groundwater; management of such demand requires a better understanding of the impacts of groundwater withdrawals on traditional cultural and biological values of aquifers. Management decisions should be coupled with appropriate hydrogeological methods to understand how to sustain dependent cultures and ecosystems. A rapidly developing groundwater basin in Central Arizona was used as a case study to investigate the impacts of management under safe yield and sustainable yield. A three-dimensional groundwater flow model was constructed and calibrated to measured steady-state and transient conditions. The calibrated model was used to make 100-year simulations of the basin with different water-use scenarios and to compare these scenarios to the concept of sustainable yield. Sustainable yield was defined as yield that would not significantly affect the availability of the groundwater system to sustain riparian habitat and perennial springs. The results of the model indicates that current levels of groundwater extraction do not exceed a sustainable yield for biological thresholds. Some of the water-use scenarios that represent regulatory limits as well as potential future water use in the study area did exceed the biological thresholds of a sustainable yield criteria.