Modeling and predicting changes of TDS concentration in Varamin aquifer using GMS software

In this research, GMS 10.0.11 software was used to investigate the qualitative changes and modeling of variations in concentration and prediction of TDS in the Varamin aquifer. In this regard, after collecting geological, meteorological, hydrological and hydrogeological data, geophysical experiments and exploratory boreholes, rainfall statistics and groundwater levels in wells, a database in ArcGIS10.5 software was created and to build the conceptual model, transmitted this information into the GMS software environment. Then based on the conceptual model, the simulation, calibration and verification of groundwater level were done using the Modflow2000 code in GMS software. Calibration results indicate that the fitting is very suitable for observed and calculated head by the model at R2=0.99. After this stage, the solute transport model was developed to evaluate the changes in TDS concentration by the MT3DMS subsystem. The results of the study showed that if the condition of operation and the entry of sewage to the western and southwestern areas of the aquifer continue to be similar, at the end of the forecast period, then the concentration will even reach 7000 mg/l, and the inadequate condition in these waters areas will be used for drinking and farming purposes.