Assessment of Regional-Scale Freshwater Availability Towards Sustainable Management in the Context of Climate Change

Freshwater availability is a key indicator of climate change in areas like the Mediterranean with growing water crises. The Umbria region in central Italy, experiencing rising temperatures and declining rainfall, is a prime local case study for assessing the impact of climate change on freshwater. In this study, we exploit two well-established, spatially distributed datasets (BIGBANG v8 and ERA5-Land) to compute net freshwater (NF) available in the region as the difference between water input (precipitation) and consumption by evapotranspiration. Both datasets show a declining regional NF trend from 1951 to 2023, with −2.03 mm/year and −1.30 mm/year rates, respectively. The decline is more marked in areas with higher average NF such as mountainous areas. Despite differences in spatial resolution, spatially averaged magnitudes from the two datasets are highly correlated (r = 0.84). They both successfully capture major drought events observed in the region since the 2000s. In addition, the study compares amounts of freshwater potentially available against anthropogenic uses to develop sustainable water management policies. Information on different water uses and estimates from modelling platforms were collected in the region. This study aims to be a proof of concept for a reliable approach serving to develop policies for sustainable water use.