In 2017, the surface water resources of central Italy suffered from a combination of dry weather and increased human extraction. Specifically, the water level of the main surface drinking water reservoir supplying the City of Rome (Lake Bracciano) is currently low and the lacustrine ecosystem is in an unstable state. The aim of this study is to describe the current state of Lake Bracciano via a multidisciplinary approach in the light of the climate and hydrological variation over the past decade. The digital reconstruction of the lake cuvette made it possible to quantify the effects of oscillations in the level of the lake on the shoreline, while the potential impact of meteorological forcing on the lake-level oscillations was investigated by monitoring anomalies in precipitation and evaporation rates. The preliminary results indicate that the present Lake Bracciano crisis mainly results from below-average precipitation since 2015, compounded by significant water extraction. Indeed, in the past 3 years, there has been almost no winter recovery phase, resulting in a total water loss of 114 millions of m3, which has never been observed before. In November 2017, the lake level reached a historic low of - 198 cm with respect to the hydrological zero (corresponding to a 13.5% reduction in the area of the lake bed responsible for self-purification), considerably below the sustainable level of - 150 cm. We conclude that the persistent low precipitation (- 50% in 2017 with respect to the 1961-1990 baseline), intense evaporation (6.7 mm/day during summer 2017), and extraction have brought the ecological state and associated ecosystem services of Lake Bracciano to conditions of serious stress.
The present state of Lake Bracciano: hope and despair
Rossi D;Romano E;Guyennon N;Ghergo S;Parrone D;Scala A;
2018
Abstract
In 2017, the surface water resources of central Italy suffered from a combination of dry weather and increased human extraction. Specifically, the water level of the main surface drinking water reservoir supplying the City of Rome (Lake Bracciano) is currently low and the lacustrine ecosystem is in an unstable state. The aim of this study is to describe the current state of Lake Bracciano via a multidisciplinary approach in the light of the climate and hydrological variation over the past decade. The digital reconstruction of the lake cuvette made it possible to quantify the effects of oscillations in the level of the lake on the shoreline, while the potential impact of meteorological forcing on the lake-level oscillations was investigated by monitoring anomalies in precipitation and evaporation rates. The preliminary results indicate that the present Lake Bracciano crisis mainly results from below-average precipitation since 2015, compounded by significant water extraction. Indeed, in the past 3 years, there has been almost no winter recovery phase, resulting in a total water loss of 114 millions of m3, which has never been observed before. In November 2017, the lake level reached a historic low of - 198 cm with respect to the hydrological zero (corresponding to a 13.5% reduction in the area of the lake bed responsible for self-purification), considerably below the sustainable level of - 150 cm. We conclude that the persistent low precipitation (- 50% in 2017 with respect to the 1961-1990 baseline), intense evaporation (6.7 mm/day during summer 2017), and extraction have brought the ecological state and associated ecosystem services of Lake Bracciano to conditions of serious stress.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
