Estimating vulnerability of water body using Sentinel-2 images and environmental modelling: the study case of Bracciano Lake (Italy)

Due to the concomitance of several factors related to progressive climate changes and to increased water management for anthropogenic usage, drastic fall in level of Bracciano Lake, a volcanic lake, 30 km northwest of Rome, was reported. In November 2017 the water level decreased 1.98m below the hydrometric zero. Vulnerability to eutrophication was investigated by determination of the lake water volume and the related phosphorus concentration. At this purpose, the bathymetry layer of the water body and the application of supervised classification of Sentinel-2 images allowed to quantify the water body and to define the coastline shape. Once calculated the hydrometric reduction in water body after the hydrometric crisis, occurred in 2017, Vollenweider model allowed to estimate nutrient concentration (around 100.93 μg/l) and the relative increase of the eutrophication status (+2.3% per liter). According to the lake water quality classification proposed by the OECD, we classified the lake as a very eutrophic lake with a hypertrophic level in the period of water crisis. The proposed methodology represents an efficient monitoring tool for assessing the vulnerability of water bodies influenced by eutrophication.