Impact of mining activities in the upper silesian coal basin on surface water and possibilities of its reduction

Due to the deposits of quality hard coal, the area of the Upper Silesian Coal Basin (USCB) has been one of the most industrialised regions in Europe for centuries. One of the most significant issues in terms of environmental impact and risks related to mining activities are the discharged mine waters. Mine water is pumped to the surface in great amount from mine workings of active underground mines both in Czech and Polish part of the USCB. In the past, the mine waters used to be discharged to nearby watercourses without systematic control of their amount and quality. It resulted in uncontrolled impacts on quality of the main rivers in the USCB. This is why a technically and economically demanding solution was adopted: discharging of mine (but also waste) waters through an artificial channel - so-called "Olza Collector" - directly to the Oder River, i.e. away of the Olza River and its minor tributaries. Automated control and dosing of waters to the Oder River depending on quality of the discharged waters and quality and quantity of the Oder surface water ensures maintaining of the total content of chlorides and sulphates in Oder below 500 mg/dm3 with the efficiency of more than 90% of days in a year.