Abstract
Bracciano Lake is one of the major water bodies of Lazio region and the eighth lake in Italy by area. Similarly to other water bodies located on the Tyrrhenian side of the Italian Peninsula, Bracciano Lake has a volcanic origin. This water body is a strategic resource for both the emergency and ordinary water supply of Rome megacity, thanks to the short distance (about 30 km). During the last years, the concurrence of climate change and anthropogenic activities led to important water level drops of the lake: the last and worst in 2017, when the lake faced the most important water crisis of its entire history, with a critical impact on the ecological system and the consequent interruption of water supply. This paper, using the inverse hydrogeological water budget (HWB) method in a GIS environment, aims to define the water budget of Bracciano Lake on a 15-year time series (2008–2022), providing a framework of climate change and human impacts on lake water levels. The outputs have been used for the simulation of lake water levels during the same period, with a focus on the drought of 2017. The variation between simulated and observed level is, on average, 2 cm and in any case never more than 28 cm. Results show the fragile balance between inputs and outputs, highlighting the need for sustainable management of both surface water and groundwater withdrawals from the surrounding aquifer.