On the role of hydrological processes on the water balance of Lake Bolsena, Italy

Lakes or reservoirs are complex environmental systems, and the sustainable management of their water resources requires advanced hydrological modelling techniques of the main state parameters (water levels and volumes, temperature, pollution level, etc.) to forecast the impacts of human activities on their natural context. Bolsena Lake in northern Lazio is a typical Italian lake environment, being a source of both environmental and economic wealth for the neighbouring area, drawing tourists and providing drinking and irrigation water. The complexity of this hydrogeological and anthropogenic system, and the current technical/scientific relevance of the several water emergencies that have occurred at the lake over the past decade, highlighted the need for a solid plan to manage the possible extreme scenarios that can affect the lake basin, including mitigation of decreases in the lake levels and for controlling lake water quality and water flow rates. The objective of this study was to assess the water budget of Lake Bolsena, accounting for the various jointly involved components, in order to model the lake levels, and to examine possible future scenarios that consider both natural and anthropogenic basin factors. Hydrometeorological data are analysed for setting such scenarios. An open-source computational model (CEQUEAU) was calibrated with the available data and then used to evaluate possible outcomes. The model simulation results demonstrated the developed hydrological model is capable of predicting water-level fluctuations with a good accuracy for both drought and flood events, identifying it as a valuable tool for basin/lake and lake/river management and simulations.