Exploring groundwater processes in Rocky Mountain headwaters

Abstract:

More than one-sixth of the Earth’s human population relies on freshwater originating in mountain headwaters, which is understood to be generated largely from snowpacks that melt throughout the spring and summer. Annual hydrographs in these regions are characterized by large peaks occurring in the spring, followed by slow recession towards winter baseflow conditions. However, atmospheric warming trends are found to coincide with earlier periods of snowmelt, leading to increased flows in spring and decreased flows in summer. This decreased ability of our ‘water towers’ to store snow late into the summer suggests that other mechanisms of storage and release may become more important in sustaining baseflows. In particular, subsurface processes leading to late summer and winter flow will become increasingly important earlier on, but are as yet poorly understood. By utilising historical data to inform a better understanding of late-season subsurface processes, we will be better prepared to predict how these mountains will temporarily store and release groundwater in a warmer climate. Here, we analyse long-term data sets from a small (Marmot Creek, Alberta ~10 km²) and a large (Bow River at Banff, Alberta ~1000 km²) basinwithin the Canadian Rocky Mountains, comparing observations with model outputs, to investigate late-season hydrological responses, and particularly the role of groundwater as a temporary storage mechanism.