The analysis of the influence of planned increase of sand output from under water in Obora sandpit on water relations of neighboring areas is conducted in this paper. The bases for the performed simulations were mathematical models based on Boussinesq equations and hydrodynamic dispersion equations. The model includes all most important factors occurring in a given area influencing the hydroisohipses system and lines of chemical pollutant concentrations. Apart from typical hydrogeological elements such as water-courses, wells, and supplying from the aeration zone, the terrains depression caused by copper ore exploitation was also considered. As results from the carried out multi-variant simulation computations, the planned sand output will not cause the formation of depression hopper and will not significantly deteriorate the quality of underground water in the area surrounding the sandpit.