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Abstract:

The aim of the research presented in this paper was the recognition of potentials and drawbacks of visible light photos taken by the Sentinel-2 satellites as a source of data for hydrodynamic issues regarding dammed reservoirs located in the Polish Carpathian foothills. The authors analyzed the photos of five reservoirs: Goczałkowice, Tresna, Dobczyce, Czorsztyn and Solina. Depending on the object’s geographic location, one can expect one or two photos taken during each 5-day period. No more than 1/5 of the taken photos of the given locations contain a non-obscured view of the water bodies. Visibility varies throughout the year along with the expected clear sky percentage; and the probability of obtaining a clear picture is lower than this value. In the Polish Carpathians, the best visibility occurs in August, while the worst in December. The chance of getting a clear view is lower during high discharge periods than in low discharge ones. In the clear photos the authors identified density currents of different nature: turbidity, reverse turbidity (i.e. clear water entering a turbid area), eutrophic and thermal. The currents can also be seen as sub-glacial ones. The shapes of the visible currents can be used for calibration and validation of hydrodynamic numerical models of the reservoirs. The authors obtained a good accordance between the shapes of the currents visible on the photos and the water velocity field predicted by a numerical simulation with the FESWMS model for the hydrological and meteorological input variables set to follow the actual conditions that day.