Changes in the surface area of lakes in the Gwda River basin

摘要

This paper presents lake surface area changes that have taken place in the Gwda River basin. The studies were conducted on the basis of the cartographic materials released since the beginning of the twentieth century until the present times. The starting point was the area of all lakes greater than 1 ha which are present on the MPHP map from 2010. The assessment of the changes in the surface area of lakes in the Gwda River basin during approximately the last 100 years was possible thanks to the use of German topographic maps, so called Messtischblatt, at a scale of 1: 25 000 released between 1919 and 1944. The area of all the studied lakes has decreased by 465.09 ha (from 12783.62 ha at the beginning of the twentieth century to 12318.53 ha at the present time). Despite the general trend of lake atrophy, in particular cases one may observe an increase in the water surface area. This is the result of hydrotechnical works leading to river and lake damming, which in turn hampers the pace of atrophy.