A groundwater model was set up for the aquifer system of the Zayandeh Rud Basin using the software FEFLOW. The main aim of the model is the volumetric description of the seepage water in dependency of the groundwater levels nearby the Zayandeh Rud River.
From the scarce geological data available, a hydrogeological model was set up. The groundwater extraction of more than 1300 springs, almost 1000 qanats and around 38,500 wells was included. Natural groundwater recharge was calculated by a SWAT model. The main recharge occurs on flat land as well as along the aquifer borders by additional mountain front recharge. Artificial recharge was included with respect to groundwater return flow from irrigation. The Zayandeh Rud River was defined as a Cauchy boundary condition.
The FEFLOW model was set up as an unsaturated and transient model with constant boundary conditions. The calibration was performed for the period from 1995 to 2009 and a statistical comparison of measured and simulated hydraulic heads was conducted for approximately 300 observation wells.
The simulation results indicate a drawdown of more than 60 metres in only 15 years, which was confirmed by the available measurements. The river leakage causes inflow into the FEFLOW model, which explains the fact that the groundwater heads near the river are less influenced by the over-exploitation. Nevertheless, without a significant decrease of groundwater extraction it is evident that the declining groundwater levels and increasing surface water leakage will continue.
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