In this time-lapse by Sentinel-2 you can see the Kaunas Reservoir (lit. Kauno marios) in Lithuania. It is the largest artificial water body in Lithuania. This is a place where we often go swimming. The lagoon and its shores belong to the Kaunas Lagoon Regional Park. This beautiful park is rich in water birds listed in the Lithuanian Red Data Book, breeds various fish, and has unique and valuable plant communities. The length of the lagoon is 80 kilometers.

Water blooms are observed every year as a sign of eutrophication, making the water unsuitable for swimming. This could be due to a variety of chemicals entering the water that are changing the ecosystem. The chemicals are various detergents, washing powders, various cleaning products – they are full of phosphorus compounds, which, when entering water bodies, promote the growth of algae. This process is usually cyclical and can be repeated in spring, summer, autumn. Each year, depending on weather conditions and the amount of nutrients entering the water, the intensity of flowering varies, affecting the processes that adversely affect the water ecosystem, could be classified as pollution. We try to find when and where the problem originates, thanks to the Sentinel-2 images. In a time lapse of last year we tried to locate the focus where the algae proliferate and the exact starting date. Our aim is to investigate this going back in time, to find out the year in which it originated, relating it to human activities in the same area.