The spatiotemporal variability of runoff generation and groundwater dynamics in a snow-dominated catchment

Abstract

Summary The intricacies of hydrometeorological process interactions with basin physiography in snow-dominated catchments may only be acknowledged through the recognition and study of the spatiotemporal heterogeneity of runoff generation and groundwater dynamics. Subsurface flow mechanisms have a direct influence on stream runoff generation. In order to better understand the coupling of these processes, the linkages between stream runoff generation and groundwater dynamics need to also be considered. This study collectively examines the spatiotemporal variability of stream runoff generation and groundwater dynamics in a snow-dominated catchment in south-central British Columbia by monitoring basin outlet flow, continuous groundwater fluctuations at 9 locations, and instantaneous flows at 42 locations throughout the stream network. Observed groundwater levels were found to be more responsive to inputs in the upper hillslopes with flow accumulation in the lower slopes, and strong groundwater level correlations with stream runoff generally decreased with increasing distances from streams. The specific discharge of reach contributing areas was found to be significantly correlated to various physiographical parameters including contributing area, an index of average hillslope flow velocity, reach length, elevation, and slope. Nested subcatchment stream runoff scaled positively in a power law relation with contributing area ( r 2 = 0.74–0.88), and sub-basin discharge was found to scale near linearly with drainage areas ranging 0.9 ha–4.74 km 2 . The findings of this study are in general agreement with the concept of the transmissivity feedback mechanism; lateral inflows to streams contributed relatively new water during periods of greater runoff contribution, whereas during the low-flow summer period, hillslopes in a hydrologically dry state produced waters that experienced longer mean residence times. In order to better understand the coupling of subsurface flow mechanisms and stream runoff generation, it is suggested that future work should emphasize spatially-intensive continuous measurements of stream network flows in combination with comprehensive groundwater level monitoring.