Groundwater Response to Snowpack Changes

Rivers with headwaters in the mountains supply freshwater to over half of humanity. Rising global temperatures, however, severely alter these sensitive systems, causing not only a loss of critical mountain ecosystems but also represents a considerable risk for local and downstream populations by affecting a myriad of industrial sectors such as agriculture, forestry, hydropower production, transportation, tourism and water supply.

Within recent years, a growing body of research has shed light on some aspects of the changes caused by global warming. These changes include an anticipated decrease in snow water equivalent (SWE); the amount of water contained within the snowpack, a shortening of the snow season, a general shift towards more rain-driven regimes, and an increase in evapotranspiration that can lead to groundwater depletion and reduced runoff. All of these changes are known to alter stream discharge, thereby affecting the water supply of downstream regions.

Stream runoff is predominantly generated by a combination of precipitation, snowmelt and groundwater discharge. Groundwater discharge is particularly important during dry seasons without snowmelt. Thus, groundwater can act as a buffer against climate extremes (such as droughts) and enhance the resilience of downstream regions.

Despite this critical importance of baseflow (that is, the assumed fraction of streamflow originating from groundwater and/or other sources such as the slow drainage of soils) in sustaining streamflow, only a few recent studies have investigated how sensitive groundwater is to changes in the cryosphere. This knowledge gap hampers our ability to evaluate the vulnerability of groundwater storage and release to global warming, with broad economic and environmental implications.

To hone the understanding of the response of groundwater to changes in the snowpack, this thesis will employ a combination of remotely sensed data, (existing) field data and modelling of a snowmelt-dominated catchment in Norway (Finse). Depending on the student's interests, this thesis will have either a focus on modelling or fieldwork.

This project can potentially be extended to other sites within or beyond Norway.

Potential research questions include:

• can we employ a mass balance approach to quantify dynamic groundwater storage?
• is there a link between groundwater storage (and baseflow), and snow accumulation and melt?