Changes in the water surface area of Lakes Udzierz and M?tasek in the light of cartographic materials

摘要

The paper presents the changes in the water surface area of Lakes Udzierz and M?tasek located in the headwaters of the catchment of the River M?tawa (tributary of the River Vistula). The assessment of the rate of changes was based on Polish and German topographic maps as well as orthophotomaps. The analysed lakes turned out to be two of the fastest disappearing Polish lakes. In the last century (1910-2010) the water surface area of Lake Udzierz decreased from 148.87 to 69.60 ha and that of Lake M?tasek from 29.5 to 0.64 ha. The average rate of loss of the lake surface area during this period was from 0.53 to 0.98% per annum. Such drastic morphometric changes in the studied lakes are, on the one hand, mainly due to poorly conducted drainage and, on the other hand, the eutrophication of the lake waters intensified by the anthropogenic impact.