Environmental repercussion of subsidence reservoirs reclamation

Subsidence basins filled with water are being formed above exploitation fields also in woodland areas leading to changes in water relations simultaneously affecting creation of environmental islands characterized by higher biodiversity in comparison with adjacent areas. Unfortunately, these types of water reservoirs from the legal point of view are considered mining damage and should thus be reclaimed. Reclamation usually consists in gravitational drainage and filling up with barren rock, appropriate relief forming and afforestation. So performed reclamation practices lead to negative effects both within the subsidence and in adjacent areas. The objective of this work was to determine the impact of reclamation based on filling subsidence with barren rock on changes in hydrology and biodiversity of nearby forest communities. For the purpose of the study two objects were selected: the existing water body and former water reservoir – at present filled with barren rock. Both are situated in Śląskie voivodship (the territory of Mysłowice and Katowice). Within the two objects, hydrological studies at two sampling points in each of the objects and vegetation sampling were performed. The DCA of 12 transects (6 in each object) and statistical analyses of vegetation showed differences between two objects in species composition, especially due to higher abundance and coverage of invasive and expansive species in reclaimed areas. Chemical analyses showed high contamination of surface waters (by e.g. SO4, Cl, Na) caused by waste deposition in barren rock and the negative effect of coal mine waters supplying the area of reclaimed reservoir.