Modeling spatial and temporal streamflow dynamics in a high-mountain catchment using the SWAT-GL model

In glacierized high mountain catchments, streamflow generation is strongly influenced by snow and glacier melt, processes especially sensitive to rising temperatures and ongoing climate change. These vulnerabilities make mountain headwater catchments a research priority; However, limited observational data and complex glacier-snow interactions often challenge conventional hydrological modeling in high-mountainous areas. Although several models have been developed to simulate streamflow dynamics in glacierized settings, many either lack comprehensive glacier representations or oversimplify them, failing to incorporate critical processes such as glacier evolution over time (e.g., glacier retreat).

To address these limitations, we employed the recently developed SWAT-GL model, which integrates a mass balance module and a glacier evolution parameterization to more accurately track changes in glacier volume and extent. Using a degree-day approach and ∆h-parameterization for glacier adjustment, SWAT-GL provides a robust framework for simulating spatiotemporal streamflow dynamics in glacierized catchments.

We applied SWAT-GL to the Valsorey catchment in the canton of Valais, Western Swiss Alps, calibrating the model with in-situ meteorological and streamflow data collected over the past decade. Our analyses revealed pronounced interannual variability in flow intermittency between climatically contrasting years, underscoring the distinct influences of glacier-fed and non-glacier-fed sub-catchments on overall runoff patterns. In particular, we identified notable differences in no-flow occurrences and seasonal streamflow recessions. Glacier-fed streams exhibited prolonged baseflow during warmer periods, while non-glacier-fed streams experienced an earlier onset and more frequent episodes of low or no-flow conditions.

Ongoing work applies future climate change scenarios to explore how continued glacier retreat will reshape these flow regimes and flow intermittency patterns. These findings will provide valuable insights into the resilience and adaptability of alpine hydrological systems.