Water quality of post-mining lakes in the Lusatian lignite mining district

摘要

Extensive open-cast mining activities in the Lusatian mining district left approximately 100 mine pits, which have to be reclaimed according to ecological and economical requirements. Cessation of sump drainage causes the rise of groundwater. Depending on the mineralogy of the sediment passed by rising groundwater the quality of groundwater and water of the connected post-mining lakes develop, locally posing high acidification risks to lake waters. As a countermeasure mine pits are flooded using allochthonous slightly alkaline or neutral surface water of the rivers Spree and Schwarze Elster. Beneficial effects comprise the displacement, the dilution and the chemical compensation of acidic groundwaters. However, low specific discharges, competing utilization demands and climatic factors strongly restrict the amount of regional surface water available for flooding. As a consequence, each individual lake's flooding schedule has to be updated and continuously adjusted to new scientific knowledge, changing demands and availability of water.