Computation of Groundwater Balance Using Numerical MLPG Method (Case Study: Birjand Unconfined Aquifer)

Having a pervasive knowledge about the groundwater balance conducts the engineers and managers to have an optimal management about these resources. In the present study, with using meshless local Petrov-Galerkin, one of the meshless methods in the field of fluid dynamic, groundwater balance is computed for a real field aquifer. The independency of this method from meshing the domain, removes the drawbacks and errors come from meshing state and improves the accuracy of results. The case study is Birjand unconfined aquifer located in South Khorasan province, east of Iran. After groundwater flow simulation and model calibration in one year 2011-2012 with monthly time step, the groundwater head is computed for each month and compared with the results of finite difference method (FDM). RMSE, MAE and ME criterion are calculated for both methods. They are 0.757m, 0.573m, -0.08m for MLPG method and 1.197m, 1.434m, 0.159m for FDM, respectively. The higher results of MLPG shows more correspondence of this method to real condition of aquifer. Finally, the input and output volume of water are computed for the aquifer. They are almost 91 and 88 MCM respectively. Therefore, the value of groundwater balance is computed. It was 3 MCM with minus sign which indicated the higher amount of output regarding to inputs.