Predicting the effects of overuse on Zarandieh plain aquifer (Markazi province, Iran) using GMS software

The studied aquifer is located in Zarandieh Plain of Markazi Province with an area of about 1200 square kilometers. Therefore, in order to identify and protect the optimal use of groundwater resources, a mathematical model of the aquifer was constructed using the MODFLOW code under the 7.1 GMS interface. For this purpose, first a conceptual model is prepared and then a numerical model based on it, based on water level changes using water table statistics of 14 piezometric wells in the region, in a time step of one month for steady state (October 2010) and a period of 12 months (November 2010 Until October 2011) for unstable state, was calibrated manually and automatically. During this stage the initial values of hydraulic conductivity (K) was optimized. At the end of calibration, in the steady state, the RMS amount reached 1.265 meters and in the unstable state, the RMS amount reached 2.145 meters, which is less than the allowable error value of ± 2.5 meters and is acceptable. Also, the validity of the model was performed in another period of 12 months (November 2011 to the end of October 2012) that at the end of validation, the RMS value was calculated to be 2.46 m. Due to the appropriateness of the RMS values of the simulated model, it has the ability to predict the future status of the aquifer. Then, after confirming the accuracy of the model in the validation phase, the future conditions of the aquifer were predicted and the results showed that in the next 3 years, with the continuation of the current trend of harvesting from exploitation wells, in some parts of the aquifer will decline.