Zmiany powierzchni jezior Pojezierza Dobrzyńskiego w świetle materiałów kartograficznych
Changes in lake surface areas in the Dobrzyń Lake District in the ligth of cartographic materials

Summary/Abstract: This paper presents the results of the analysis of changes in the surface area and number of lakes in the Dobrzyń Lake District over the past 110 years. In the analysis cartographic materials from three periods were used : 1900 – 1915, 1980 – 1985 and 2009, making it possible to capture changes in the surface area of lakes and determine their trend. The results indicate a decrease in the surface area of the studied lakes in the mentioned period of time. The biggest changes occurred in the case of the smallest lakes of surface area less than 5 hectares. It was found out that the decrease in lake surface area in specific parts of the Lake District was uneven. The largest decrease occurred in the southern, north-eastern and particularly south-eastern parts of it. Changes in the surface area of individual lakes ranged from a few to several tens of percent (in the case of lake disappearance it was one hundred percent). The most common consequence of these changes was an increase in the lakeshore length due to the creation of peninsulas and bays. In several cases, the emergence of small islands was also observed. The trend of lake surface area decreasing indicated in the paper is consistent with the results obtained by other authors in other parts of Poland.

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