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Li, Hongyi

University of British Columbia

Study of cross-site variabilities and similarities of catchment storage-discharge relation provides insights into the drivers and causes of such relation, generalizable to a wide range of climatic and physical settings. In this thesis, two studies were conducted using large-sample hydrology comparative analyses to enhance the understanding of the drivers and causes of the functional relations between catchment storage and discharge. Hydrograph recession analysis was the primary analytical tool in this thesis. It was applied to determine the catchment recession flow dynamics, and to build the mechanistic understanding of the cause of diverse storage-discharge relations observed in different climatic and physical settings. Findings suggest that the nonlinearities of streamflow recession (and that of storage-discharge relation) strongly depend on belowground attributes and slope in rain-dominated medium size catchments, and strongly depend on slope and snowmelt characteristics in snow-dominated medium size catchments. In large catchments (i.e., catchment area larger than 1000 square kilometers), the attributes related to magnitude and timing of input water (e.g., water surplus, aridity index, maximum snow water equivalent) have larger relative influences, than belowground attributes, on streamflow recession dynamics and storage-discharge relation. Meanwhile, the results show that at low flow condition, hillslope bedrock groundwater contribution to main stream may become a major source of low-flow, and its absence or presence determines the functional nonlinearity of recession dynamics and storage-discharge relation. With an increase in the contribution of hillslope bedrock groundwater—relative to riparian groundwater—to low-flow discharge, the nonlinearity of recession hydrograph increases, leading to a higher catchment-scale resistance to streamflow drought during dry periods. The findings expand the understanding of catchment-scale groundwater flow pathways generating low-flow, with implications to identify where and why catchments are vulnerable to drought under prolonged dry periods.

Text

2024-01-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83668

Geological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/