The Occurrence of Water Reservoirs as an Indicator of the Development of Water Resources Under Conditions of Varied Anthropopressure

The research was conducted in the Upper Silesian Anthropogenic Lake District, which covers an area of 6766 km2 in the central part of southern Poland. Within the anthropogenic lake district, there are water bodies in former mineral workings, reservoirs impounded by dams, water bodies in subsidence basins and hollows, levee ponds, various types of industrial ponds, as well as water bodies created as a result of river regulation. In 2025, an inventory identified 11,589 water bodies (including 5556 with a surface area greater than 0.1 ha; total area 200.28 km2), with a cumulative water surface area of 202.61 km2, i.e., significantly more than in earlier surveys from the 1960s (3097 water bodies with an area greater than 0.1 ha; total area 113.4 km2) and the early 21st century (4773 water bodies with an area greater than 0.1 ha; total area 185.4 km2), which demonstrates a rapid increase in both the number and area of water bodies as a result of anthropogenic pressure, in the complete absence of natural lakes. The volume of anthropogenic reservoir storage, determined at 614.14 million m3 of water (442 million m3—a value calculated on the basis of measurements of 116 water bodies; another 170 million m3—a value estimated for 11,473 water bodies with a very high computational uncertainty), corresponds to a water layer with a thickness of 90.8 mm across the entire Upper Silesian Anthropogenic Lake District and is comparable to 12.6% of the mean annual precipitation within its boundaries for the 1991–2020 multi-year period. These values and parameters in general can certainly be put forward as indicators of anthropogenic environmental changes, since water bodies, as an integral part of the cultural landscape, can be considered an indirect measure of the intensity of human activity.