Investigation of the Effects of Garmsiry Water Transfer Project on the Behavior of Mehran Aquifer using GMS Software

The aim of this study was to investigate the effects of the Garmsiry water transfer project (97 MCM per year from Sirvan River) on the behavior of the Mehran aquifer. For this purpose, the Groundwater Modeling System (GMS 7.1), which is one of the most suitable tools to simulate the groundwater level, was used. To develope the GMS model, input data including; aquifer boundary, Digital Elevation Model (DEM), bedrock level, groundwater level, groundwater withdrawal from wells, hydraulic conductivity, and groundwater recharge layers were prepared by ArcGIS 10.4. These layers were used to conceptual model construction using the MODFLOW codes in GMS interface. For steady and transient state calibration, and validation of the model, groundwater level changes resulting from the model are compared with piezometric measurements for the period Oct-2016, 2016-2017, and 2017–2018, respectively. The results showed a good accuracy in calibration and validation model, respectively, between the simulated and observed groundwater levels (ME=0.12, RMSE=0.84) and (ME=0.57, RMSE=1.4). Three scenarios including, 10, 15, and 20 percent of agricultural water return were conducted to evaluate the effects of Garmsiry water transfer project. The results showed that the groundwater level of Mehran aquifer will be increased 1.43, 2.22, and 3 meter per year in scenarios 1 to 3, respectively. This issue is very important along with the low storage coefficient of the Mehran plain aquifer, and can be a warning for severe drainage problems in the near future. The results of this study showed that the central and southern parts of the plain would have drainage problems less than ten years after the operation of the irrigation network.