Alpine Groundwater – Pristine Aquifers Under Threat?

Abstract:

Glacier and permafrost retreat are prominent climate change indicators. However, the characteristics of climate and hydrology in mountain areas remain poorly understood relative to lowland areas. Specifically, not much is known about alpine groundwater, its recharge and water quality variations, as these remote reservoirs are rarely monitored. As global temperatures rise, glaciers and permafrost will continue to retreat forming new sediment deposits and changing infiltration conditions in high alpine terrain. Climate change impacts the hydro-chemical composition of alpine waters, accelerates weathering processes, and potentially triggers mobilization of pollutants. Accordingly, we monitored groundwater quantity and quality parameters of an alpine porous aquifer near the Tiefenbach glacier in the Gotthard Massif in Switzerland. The goal of this research was to assess quality and seasonal storage dynamics of groundwater above the timberline (2000 m).

To translate hydrological science into an ecosystem service context, we focused on four attributes:

1. Water quantity: observations of groundwater level fluctuations combined with analysis of contributing water sources based on stable isotope analysis to give a quantitative understanding of origin and amount of water,
2. Water quality: groundwater level, groundwater temperature and electrical conductivity were used as proxies for sampling of hydro-chemical parameters with automated water samplers during primary groundwater recharge periods (snowmelt and rainfall events),
3. Location: Alpine terrain above the timberline, especially recharge into/out of an alpine porous aquifer at a pro-glacial floodplain and
4. Date of annual melt (albedo effect) and timing of flow (snow- and icemelt from May to September) and groundwater recharge during the growing season.

The study found that the summer groundwater temperatures depend on the date of annual melt and are more sensitive to climate forcing than lowland groundwater temperatures. Furthermore the groundwater level determines the groundwater composition as indicated by the electric conductivity. These two observations taken together help form a better understanding of the hydrochemistry of the system, and provide useful parameters for understanding the impact of climate change on alpine groundwater.