Assessing climate change impacts on pristine glaciated catchments in the Alpine region using indicators of hydrological alteration

Glaciers sustain the global water cycle and preserve natural ecosystems by acting as reservoirs that release consistent freshwater during dry periods. This meltwater supports biodiversity, nutrient balances, river streamflow modulation, and human activities such as irrigation and water supply. Currently, accelerating glacier melt has become an alarming phenomenon, with global glacier mass loss of around 5% since 2000. This contributes to sea-level rise and threatens water supplies for over 2 billion people. In this context, this study aims to assess the impacts of climate change on pristine glaciated catchments in the Apline region, where accelerating ice loss threatens spring and summer river flows that are vital for ecosystems and societies. Using the ROBIN dataset, we calculated seasonal (i.e., spring and summer) indicators of hydrologic alterations (magnitude, timing, extremes) comparing pre-climate change (1931–1950) and post-climate change (1977–2012) baselines for 20 pristine catchments with areas ranging between 22 Km2 -981 Km2.

Results in spring and summer reveal high variability in key flow indicators (including mean monthly and seasonal flows, rise and fall rates, In addition to  seasonal minimum and maximum flows) especially across the six largest catchments in the study area (> 345 Km2). Comparing the post-climate change period (1977–2012) to the pre-climate change baseline, results indicated increased interquartile ranges and greater uncertainty of mean values associated with seasonal flow rates. Additionally, they showed irregular occurrences of extremes regarding their timing, frequency, and duration of high and low pulses, as well as flow reversals, for all catchments. These findings indicate increased dispersion, extremes, and instability associated with a meltwater buffer zone.

These results highlight that climate change has a strong impact on pristine Alpine glaciated catchments with limited human intervention, showing how increased glacier melting rates trigger hydrological fluctuations with pivotal implications on water resources management. This situation requires effective adaptation measures concerning increased ice melting rates.