Conjunctive simulation of surface water and groundwater using SWAT and MODFLOW in Firoozabad watershed

One of the most essential groundwater model components is accurate information about the recharge values within the input data, often introduced to a groundwater model as a percentage of rainfall on aquifers. Recharge values are influenced by many temporal and spatial factors. This paper suggests the use of a SWAT model for surface water simulation and the estimation of recharge rates. In this research, sensitivity analysis, calibration, validation and uncertainty analysis of results were performed by SWAT-CUP software. Due to the semi-distributed features of SWAT and the difficulty of calculating groundwater distributed parameters, recharge values estimated by SWAT were used in a MODFLOW model for groundwater simulation at steady and unsteady states. This method was applied in the Firoozabad basin, which is one of the most suitable agricultural basins for modeling surface water and groundwater in Iran. After MODFLOW model calibration, hydrodynamic coefficients of the aquifer were determined and the sensitivity of the model was checked for hydraulic conductivity and discharge rate of wells. In order to prove confidence, the model was validated. SWAT and MODFLOW models were successfully tested and the results of the combination of the two models were found to be acceptable.