HYDROGEOLOGICAL EVALUATION AND MANAGEMENT OF SARVESTAN BASIN, BY UNGW MODEL

The alluvial plain of Sarvestan bears the sole source of potable water in Sarvestan county, Fars Province, Iran. In recent years, due to extended heavy pumping, the groundwater storage has been reduced continuously. The UNGWM (United Nation Ground Water Model) is used to evaluate the hydraulic characteristics of the Sarvestan aquifer and its future response to various regimes of recharge and discharge. The model is a finite difference solution of differential equations for the two-dimensional, isotropic, nonhomogeneous transient flow of water in a porous medium. The aquifer parameters are determined through a combination of visual and rational comparison of simulated and observed groundwater contour maps while adjusting the aquifer boundary inflow-outflow rates at the aquifer recovery period. To validate the parameter values several simulated isopotential maps are compared with observed ones by optimizing the infiltrated rainfall rate into the aquifer. Using the established parameters values, boundary inflow-outflow rates and infiltrated rainfall rate, the annual well hydrographs were simulated. A very good match was found between simulated and observed hydrographs in terms of trend, fluctuations and values. The response of the aquifer to some dictated regimes of discharge and recharge was predicted. The critical zones where pumpage must be prevented are specified and the location of production wells to be drilled in the future is also defined. The UNGWM is validated as a valuable tool for groundwater resource assessment.