The impact of forests on the evolution of water resources in the mid-altitude Alps from the middle of the 19th

Abstract

Since the Industrial Revolution, a substantial part of the land in mid-altitude mountain areas has been abandoned to woodland. The forest intercepts and retains a certain percentage of rainfall on its foliage, thereby reducing the amount of water actually reaching the ground. The gradual transformation of the landscape over recent decades has therefore had an impact on the transfer of atmospheric water into a form that can be used as a resource. The present study, conducted at the scale of the Chartreuse massif (Pre-Alps, France), examines annual precipitation, the role of the forest in intercepting this precipitation, and changes in the extent of the forest cover. The impact of the extension of the forest cover from the middle of the 19 th century on the amount of water lost through runoff and on groundwater reserves can thus be evaluated. The study shows that since the middle of the 19 th century the extension of the forest cover in the Chartreuse massif has increased water losses through interception by almost 100 mm per year. It also reveals that over this same period water losses have not been compensated for by an increase in precipitation. In short, the hydrological balance has been considerably modified, with the amount of water available for runoff and groundwater reserves being less than that generally calculated simply from meteorological data records. © Journal of Alpine Research.