UBC Theses and Dissertations
Stream-catchment connectivity and streamflow dynamics in a montane landscape Szeftel, Pascal
The concept of hydrologic connectivity provides a temporally dynamic aspect to an otherwise static description of streamflow generation processes. The research presented in this dissertation focuses on the linkages between slopes, riparian zones and streams – the three main constitutive landscape elements of steep montane catchments – and the ways in which hydrologic connectivity affects hydrological processes. The research was conducted in Cotton Creek Experimental Watershed (CCEW), a snow-dominated meso-scale catchment located in the Kootenay Mountains, south-eastern British Columbia, Canada. First, the controls on slope water delivery to the stream were examined across a range of flow regimes. The spatial patterns and their dominant controls shifted from high to low flow. Catchment contributing area and slope length were good predictors of streamflow generation during high flow periods. At low flow, a new topographic index reflecting the spatial organization of flow pathways within a catchment was the dominant control on streamflow generation. Second, the dynamics of coupling between slopes, riparian zone and stream were examined through analysis of streamflow diel fluctuations. Periods representing high, intermediate and low baseflow were selected to investigate the dominant controls on diel fluctuations at nine stream gauges arranged in a nested design. Streamflow diel fluctuations were generated by evapotranspiration, the diurnal pattern of which was represented using vapour pressure deficit measured at a weather station within the catchment. Response times between climatic forcing and the various stream gauges revealed that both in-stream wave advection and dispersion processes, and transient storage processes in the riparian aquifers needed to be accounted for to explain spatio-temporal patterns of streamflow diel fluctuations. Last, the influence of slope water contributions to the stream on modelled solute transient storage and in-stream transport was examined. It was found that calibrated parameters representing transient storage vary systematically with the assumed magnitude and location of water fluxes to and from the stream.
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