Planowana kopalnia odkrywkowa na złożu węgla brunatnego „Oczkowice” zagrożeniem dla gospodarki wodnej i środowiska południowo-zachodniej Wielkopolski

The "Oczkowice” brown coal deposit composed of Neogene sediments was documented between 2011-2014 in SouthWest of Wielkopolska region. The lignite deposit, located between Miejska Górka and Krobia communities, occur 110-140 m below the surface. The designed open-pit mining requires the Quaternary and the Neogene-Paleogene aquifers to be drained and depleted up to the depth of 115-165 m for at least 50 years. The article is based on a hydrogeological expert report (Dąbrowski et al., 2015) and presents both analytical and model calculations as well as potential risks to the environment and water management of south-western Wielkopolska region. According to the expert estimation, the initial output resulting from draining of sector I would reach 4930 m3/h (81.7 m3/min). Thereafter, it would be reduced to 3520 m3/h (58.7 m3/min) at the end of sector I mining. The radius of depression cone of the Quaternary structures would be up to 3-10 km far away from the open-pit but it would be widespread by ca. 20-25 km in the Neogene-Paleogene basins. According to the calculations the groundwater losses caused by the "Oczkowice” open-pit draining would attain 59% resources of the Quaternary structures and 92% of the Neogene-Paleogene basins in the Gostyński district and 45% and 62%, respectively, in the Rawicki district. Reducing the piezometric pressure of the Neogene-Paleogene basins would result in increasing the chloride water ascension of the underlying basement and consequently its discharge to rivers.