DOI: 10.5593/SGEM2014/B12/S2.135


R. Machowski, M. Rzetala
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-08-7 / ISSN 1314-2704, June 19-25, 2014, Book 1, Vol. 2, 1059-1066 pp

The Silesian Upland (southern Poland) is an area where underground coal deposits as well as zinc and lead ores are mined (in the past, iron ores were exploited there as well). Subsidence basins form in places where minerals are mined below the ground surface. Purposes of the study included assessing the impact of underground mining on the rate of surface subsidence, examining the conditions in which water bodies form in subsidence basins and determining the role of such basins in shaping habitat conditions and biodiversity. Within the framework of field work, detailed geomorphological and hydrological mapping was carried out, floristic composition was determined and the animals present in the area were characterised. Cartometric analyses were carried out based on the cartographic material collected. Laboratory tests were also conducted with respect to both water (using the potentiometric, spectrophotometric, turbidimetric and flame photometry methods) and sediments (using sieve analysis, the combined areometric-sieve method, INAA and ICP). The study revealed that in the region, a total area of more than 1000 km2 is threatened with ground deformation and the depth of some basins exceeds 30 meters. Water bodies at the bottom of subsidence basins exhibit morphometric parameters that depend on the size of the subsidence and their shorelines are most often oval in shape. Very small and small water bodies prevail. A vast majority of them have areas which do not exceed 10 hectares. They are also fairly shallow (usually up to 2–3 metres) and greater depths are very rare. Water bodies in subsidence basins alter the local water cycle significantly. These hydrographic phenomena are undoubtedly a new element that contributes to changes in the direction of water migration in the area in question. The water bodies examined were subject to transformations at each stage of the development of the subsidence zone. It has been found that they set a new erosion base level and act as local sedimentary basins. The bottom sediments accumulated in such water bodies are significantly contaminated, particularly with heavy metals such as lead, zinc and cadmium. The studies conducted have demonstrated that these water bodies may fulfil functions similar to natural lakes. The changes triggered by land subsidence affect the evolution of vegetation, and in the final stage, aquatic and land vegetation ecosystems are shaped. In the wake of these changes, many new animal species, both vertebrates and invertebrates, migrate into the area.

Keywords: lakes, water reservoirs, water body, subsidence basins, bottom sediments, human impact, Silesian Upland