Low-flow behavior of alpine catchments with varying quaternary cover under current and future climatic conditions

Arnoux, M., Brunner, P., Schaefli, B., Mott, R., Cochand, F., & Hunkeler, D. (2021). Low-flow behavior of alpine catchments with varying quaternary cover under current and future climatic conditions. Journal of Hydrology, 592, 125591. https://doi.org/10.1016/j.jhydrol.2020.125591

Alpine environments are particularly vulnerable to climatic warming, and long term observations suggest a shift
of snow-influenced river discharge towards earlier periods of the year. For water resources management, the
seasonal patterns of discharge in alpine areas are particularly relevant, as the shift to lower flows in summer and
autumn combined with increased water demand could lead to water shortage in downstream catchments. The
storage of groundwater in alpine catchments could significantly modulate how changing climatic conditions
influence the annual streamflow regime. However, groundwater storage and its buffering capacity in alpine
areas remain poorly understood. Moreover, studies on how climate change will impact water resources in alpine
areas rarely consider the influence of geology.
In this paper, catchment geology is used as a basis for the classification of future summer low flows behavior
of several alpine catchments in Switzerland. Based on the analysis of the relationship between low-flow indicators and geology, the role of unconsolidated quaternary deposits is explored. We show that quaternary
deposits play a critical role in the seasonal storage of groundwater, which can contribute to rivers during lowflow periods. Three climate change simulations based on extreme RCP 8.5 scenarios are fed into a conceptual
hydrological model to illustrate the buffering role of groundwater. Past and future low flows normalized by
mean past and future streamflows appear correlated with the percentage of unconsolidated quaternary deposits.
These results highlight that catchments with high groundwater contribution to streamflow relative to precipitation will have a slower decrease in future summer discharge. Therefore, we propose two indicators that can
be used to anticipate the response of future summers low flows in alpine areas to climate change: the current
winter low flows and the percentage of unconsolidated quaternary deposits of the catchments.