Hillslope hydrology and runoff processes in a subarctic, subalpine environment

Abstract

<p>Within the subalpine zone of a subarctic basin, hydrological processes were studied on four hillslopes within 5 km2 in an attempt to determine the factors that cause the variability in the magnitude and timing of water balance components. The hillslope was chosen as the scale of study as it links process operating at the point with streamflow, and exhibits strong contrasts in microclimate, vegetation, frost and soils, providing an ideal natural laboratory. Hillslopes showed strong asymmetry in the timing and magnitude of processes during the melt and summer period. On slopes with well drained soils and seasonal frost, vertical hydrological exchanges predominate over the entire year and slopes rarely contribute runoff for streamflow. In contrast, hillslopes underlain with permafrost and/or poorly drained soils with a capping organic layer produce strong lateral fluxes. Water balance information highlighted the principal factors that lead to differences in process magnitudes and timing. This information is important in understanding basin hydrology, as streamflow is a summation of lateral fluxes from slopes. The presence of ice-rich layers blocking soil interstices encourages runoff by restricting drainage. Runoff exhibits a two-layer flow system consisting of quickflow (pathways in the porous organic layer, pipes, rills, and interconnected depressions) and slowflow (pathways in underlying mineral soils and highly decomposed and compacted peat). Quickflow controls the shape and timing of the runoff hydrograph, which is influenced by properties of hillslope wetness and organic layer thickness. Recession analysis revealed variable source areas for runoff generation and highlighted the role of wetness-controlled hydrologic connectivity of a slope segment. Results from this thesis have implications for water resource inventories and predicting hydrologic behaviour of subarctic, subalpine hillslopes.</p>