Detection of lake shoreline active zones and water volume changes using digital lake bottom model and water level fluctuations

The article presents an assessment of water level fluctuations in eight lakes located in the Bory Tucholskie National Park (Poland). Mann-Kendall and Sen tests were applied to analyze the extent and direction of lake water level changes. For the purpose of detection of shoreline active zones, digital lake bottom models were developed based on bathymetric measurements. They were integrated with catchment digital terrain model, developed based on data from Airborne Laser Scanning. In analysed period, water levels in the majority of lakes showed a decreasing tendency, as a result of climate change. An increasing tendency was only observed for two lakes caused by the activity of beavers (castor fiber). The study permitted the identification of active shoreline zones with long-term exposure to drying and flooding. These zones are of the highest importance from the point of view of the functioning of water and water-dependent ecosystems, particularly protected species.