ABSTRACT
During and after the process of artificial recharge by flooding of a former open pit, oscillations of the water level, caused by seasonal effects or management strategies are inevitable. These oscillations imply oxygen input by freshwater and air, which causes pyrite-oxidation in the surrounding sediments and leads to acidification of both groundwater and the flooded lakes. To quantify the volume of the aerated pyrite bearing sediment and the volume of freshwater input due to the predicted annual surface water oscillations of 5–8 m in the flooded lignite-mine Lohsa II, a two-dimensional vertical model was built up with PROCESSING MODFLOW. The strong lateral migration of the shoreline due to the low morphologic gradient was simulated by the reservoir package. The scenarios were evaluated with respect to the resulting volumes of infiltrated freshwater during rise of surface water levels and with respect to the resulting volumes of temporary inundated and dewatered sediments.
