FIELD-BASED UNDERSTANDING OF ALPINE AQUIFERS AND THEIR REPRESENTATION IN HYDROLOGICAL MODELS (Invited Presentation)

The headwaters of large mountain ranges are considered as ‘water towers’ because high precipitation (P) driven by orographic effects and low evapotranspiration (ET) due to the lack of extensive vegetation cover, combine to create a large moisture excess in these regions. This high moisture excess (= P – ET) can in turn recharge groundwater if there are aquifers with sufficient storage capacity present. Recent studies in mountain ranges around the world have shown that common alpine landforms consisting of coarse blocky sediments, such as moraine, rock glacier, and talus slopes, can function as surficial aquifers and further sustain the baseflow of first-order streams during the cold or dry season, when there is minimal snowmelt, glacier melt, or rainfall. An analysis of eighteen river basins in the Canadian Cordillera show that the winter baseflow in these rivers have not changed over the past several decades despite the changing climate in the region, hinting at the possibility of alpine aquifers providing a buffering mechanism against climate change. We will present a brief synthesis of field-based understanding of the hydrogeological functions of alpine landforms, and a roadmap for representing these functions in practical hydrological models to help guide water resource management policies under the present and future conditions.