Investigation of quantitative changes in the groundwater table of Miandoab plain affected by surface and groundwater resources management using the MODFLOW-NWT mathematical model

Need for groundwater in recent decades has led to the development of various strategies for managing surface water resources and proper use of groundwater. In this study, the groundwater aquifer model of Miandoab plain was prepared by MODFLOW-NWT model. After calibration and validation, three scenarios were investigated. In the first and second scenarios, increase of 10 % and 20% of irrigation efficiency in the plain and reduction of pumping from groundwater was applied, respectively. In the third scenario, preventing pumping water by pump engine from rivers of Siminehrood and Zarinehrood and providing water requirement from groundwater resources was applied. In the first and second scenarios, with increasing efficiency, total water consumption can be reduced from 924 MCM in current situation to 776 and 664 MCM, respectively. By providing 642 MCM of surface water, pumping water from groundwater could be reduced by 148 and 282 MCM relative to the current situation, respectively. The results showed that from amount of water that is no longer pumped, the amount of 34 and 41 MCM are exited as underground flow from downstream toward Lake Urmia, respectively, amount of 40 and 51 MCM are discharged into surface water resources, respectively, and the rest is stored in the plain. With continuing this approach after 5 years will lead to swamp in middle of plain. The amount of agricultural return water in current situation is 33% and in the first and second scenarios are 28% and 20%, respectively, which relative to the current situation have been decreased by 5% and 13%, respectively. In the third scenario, by increasing pumping from groundwater, the average level of groundwater went down by 1.5 and 3 meters after 1 and 5 years, respectively, but it provided 495 MCM to restore Lake Urmia after 5 years.