Integrating Field-Based Knowledge of Alpine Aquifers in Basin-Scale Hydrological Models

Abstract

Talus and moraine serve as vital groundwater reservoirs, with their associated capability to modulate the baseflow of major rivers that originate in headwater environments. Recent field-based studies conducted in the Canadian Rocky Mountains have identified a nonlinear storage-discharge relationship expressed by these surficial alpine aquifers and the importance of their spatial positioning and extent in headwater environments. However, few studies have tried to upscale our current small-scale understanding of these surficial units, to better understand how their storage-discharge dynamics influence basin-scale (i.e. 10^3-10^4 km^2) hydrology. This study aimed to develop a means to integrate several representative features associated with alpine aquifers into a basin-scale hydrological model to potentially improve its capability to estimate and predict the baseflow of mountain rivers. Specifically, this study developed a simple object-oriented image classification workflow to map the spatial extent and distribution of talus and moraine, among other alpine landcover, in addition to validating the capability of a previously discerned simple exponential function to emulate the aforementioned groundwater storage-discharge relationship expressed by alpine aquifers. The resulting object-oriented workflow did well to capture the spatial variability of the aquifers present in the 2228 km^2 Upper Bow River Basin in Alberta Canada, yielding an overall accuracy rating of 90%, while providing an efficient means to extract the aquifer’s spatial characteristics. The exponential function was then tested in a small first-order watershed in the Canadian Rocky Mountains and simulated watershed’s groundwater storage-discharge dynamics to a similar accuracy compared to a distributed physically-based groundwater flow model implemented in the same area. This suggests that the function potentially has the capacity to be integrated as the new baseflow function in a basin-scale hydrologic model and likely improve its capability to accurately estimate and predict the baseflow of mountain rivers. The underlying framework of the Modélisation Environnementale communautaire (MEC) - Surface Hydrology (MESH) model, a basin-scale hydrological model widely implemented in alpine regions in Canada, is presented to demonstrate how these representative features associated with alpine aquifers could be integrated into such a model.