Changing the geometry of basins and water resources of Lakes Gop?o and Ostrowskie under the influence of anthropopressure

摘要

The paper presents the changes that have occurred in the morphometry of Lakes Gop?o and Ostrowskie, which are locatedin central Poland. The analysis covered the period characterised by increased human interference into the water cycle, which hasbeen taking place continually since the mid-eighteenth century. On the basis of available cartographic materials (aerial photographs,topographic maps, bathymetric charts of the lakes) and the authors’ own field measurements digital terrain models were developedfor the immediate environment of the surveyed lakes. These models, in turn, were used for measuring basic parameters characterisingthe external dimensions of the lakes (surface area, length and maximum width, shoreline length) and their underwater relief (volume,maximum and average depth). In addition, the selected indicators of the shape and form of the lake basins were determined. The resultsshowed a drastic reduction of water resources of the two lakes. The basin of Lake Gop?o covers only the deepest parts of the formerreservoir, accounting for only 23.3% of the lake before 1772, and 32.5% of its former volume. In the case of Lake Ostrowskie the surfacearea and volume decreased, respectively, by 23.5% (74.9 ha) and 21.3% (6 695 000 m3). Such large changes in surface area and volume ofboth lakes have contributed to significant changes in other morphometric parameters and indicators. In particular, significant changeswere observed in relation to such morphometric characteristics as length and maximum width, as well as average and maximum depth.