Anthropogenic change in water bodies in the southern part of the Silesian Upland

The paper analyses the anthropogenic change in water bodies in the southern part of the Silesian Upland as exemplified by the town of Knurów. The assessment was based on topographic maps from the years 1827-1828, 1928-1936, 1960 and 1993, and on a 2011 orthophotomap. The cartographic materials used were processed as required for analysis purposes. Maps were calibrated in the Quantum GIS program on the basis of map corner coordinates and using the common points method. In Knurów, four main types of water bodies were distinguished with respect to their origins: reservoirs impounded by dams, flooded mineral workings, industrial water bodies and water bodies in subsidence basins and hollows. Historically, the first water bodies to appear were reservoirs impounded by dams, which dominated until the 1930s. They later fell into disuse and were completely dismantled. Water bodies in mineral workings formed in the early 20th century and were associated with the excavation of raw materials for producing bricks. The period of their greatest significance were the 1960s, when they constituted slightly more than 46% of water bodies in total and accounted for nearly 40% of overall surface area. At the end of the 19th and at the beginning of the 20th century, industrial reservoirs began to appear. Within the town of Knurów, those were sedimentation tanks that held mine water, washery effluent, backfill and cooling water, fire-fighting water pools and tanks, tanks at sewage treatment plants, industrial water tanks and others. Presently, these account for 41.4% (29) of the total number of water bodies and have a total surface area of 32.0 ha (25,2%). Within the study area, water bodies in subsidence basins and hollows only began to form in the second half of the 20th century. In 2011, such water bodies numbered 38 (54.3%) and occupied an area of 90.4 ha (71.2%).