ABSTRACT: Residence time characteristics for different runoff generation processes in a small forested headwater catchment, Southwestern British Columbia.

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Abstract

A clear method to use runoff generation for predicting hydrological behaviour such as varying water residence time both spatially and temporally at the watershed scale is still lacking. This study seeks to unify spatial and temporal scales of runoff generation processes and aid in the transfer of hillslope scale studies to the catchment scale to be able to better predict catchment behaviour and therefore stormflows and flooding based on physical measurements. The following questions are addressed by this study: (1) can we predict how long precipitation input water will reside in an area of interest? (2) what pathway does the water falling on that area follow? (3) What are the first order controls on the run-off dynamics (pathways and residence time) for the dominant runoff generation process identified in the area of interest? Artificial tracers including Potassium Bromide and fluorescent dyes Rhodamine-WT and Uranine were applied to three areas chosen based on topographic and soil depth characteristics to represent different dominant runoff generation processes. Tracers were applied equally over the designated areas during a 3 hour period prior to the onset of a rainfall event to mark a pulse of water and hence directly measure residence time. Breakthrough was measured at a v-notch weir locate at the bottom of the catchment using automated probes, water samplers and water level recorders. Rainfall was measured below the canopy and in a nearby clear-cut. In addition 2 weirs measured input above the study area and a number of piezometers fitted with automatic water level recorders were placed within the study catchment. The first round of tracer applications occurred on January 4th 2006. Intense data collection has shown little or no difference in the residence time associated with different runoff generation mechanisms during wet initial conditions followed by high rainfall input.

Bibliography of Canadian Geomorphology