Investigation of the artificial recharge effect by injection well on the level of unconfined aquifer using the MODFLOW model (case study: Birjand plain)

According to the reduction of water level in many aquifers of Iran due to irregular extractions from these sources, implementation of the restoration and balancing plan for aquifer management is important particularly in arid and semi-arid regions. Artificial recharge by injection well is one of the management strategies available in this project that directly stores water in aquifers. The purpose of this study was to investigate the effect of injection wells on the unconfined aquifer of Birjand plain using MODFLOW-2000 numerical model in unsteady state conditions and based on injection of the annual runoff volume of the plain. In this regard, information about hydrodynamic characteristics of aquifer including hydraulic conductivity and specific yield, observation wells, extraction wells, aquifer surface recharge, top elevation of aquifer, bedrock and drainage was prepared then level of aquifer with The MODFLOW-2000 model was simulated in GMS 7.1 in steady state and saturated environment during 2010-2011. After simulation, the model was calibrated by manual calibration method and the results of steady state was entered as input of unsteady model and was validated in the 2011-2012 period. At the end, Artificial recharge management scenario was added to the model by injection well method with using 20 wells with discharge equal to 1909.61 m3/day for each well in one year. The validation results show the model's ability to simulate water level under unsteady conditions. Also, simulation of artificial recharge plan with injection wells showed that by applying this scenario, the level of water in all observation wells will increase on average 77 cm.