SWAT- based Recharge Estimation in Inverse Groundwater Modeling

SWAT- based Recharge Estimation in Inverse Groundwater Modeling

In arid and semi-arid environments, the amount of recharge received by aquifers is far more critical to the sustainable use of water than it is in humid regions. Reliable estimates of recharge, while directly affecting the accuracy of a groundwater model, are often unavailable or costly to obtain. This study explores how recharge estimation and its zonal patterns could affect the performance of a groundwater simulation model. For this purpose, Soil and Water Application Tool (SWAT), a semi-distributed hydrological model, is used to estimate recharge and its spatio-temporal distribution. The groundwater model is calibrated by using a two-step procedure where hydraulic conductivity is estimated first in a steady-state mode and is used then in a transient mode to calibrate the parameter of specific yield. The methodology was applied in Dehloran Plain located in west of Iran using the MODFLOW modular flow simulator in which the PEST method is used for auto-calibration. Results indicated that when SWAT was used for recharge estimation, the model did relatively well in simulating monthly water table in observation wells. Also, the effective recharge rates estimated by SWAT were the best estimates of the long-term recharge rates in validation stage.