Groundwater resources decline in Apennine Mountain areas (central Italy): climate change or hidden consumer?

The study aims to investigate the role of intensive forest growth, which began around the middle of the 20th century in northern Apennines (central Italy), in the decline of groundwater resources. The method, based on the crop evapotranspiration, considers different land use categories and their areal changes over time. Few studies in this sector of the Apennines have assessed the impact of forest growth on groundwater resources in mountain areas, mainly due to the difficulty of estimating crop coefficients in this type of contexts. Two model approaches, one of which also considers snow storage and melting, were used to quantify the impact of forest cover on groundwater recharge in the study area. The results suggest for the first time that forest growth over the last 60 years has negatively impacted the availability of groundwater resources by reducing groundwater recharge; specifically, the analysis performed during the last decades within one test site yielded average values of annual water loss between 6% and 16% of the annual spring discharge, via a lumped-parameter model and by water budget, respectively. However, the influence of forest growth could be even more significant when considering other parts of the study region. The developed approach is particularly flexible and generally applicable to other contexts.