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Runoff generation in a steep snow-dominated watershed in Alberta's southern Rocky Mountains
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- Author / Creator
- Spencer, Sheena A
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Star Creek is a snowmelt-dominated, steep mountain watershed with shallow soils, deep glacial till, and fractured sedimentary bedrock in the eastern slopes of Alberta’s Rocky Mountains. Measurements of streamflow quantity and chemistry at variable scales, water table dynamics, and precipitation were used to describe the first order controls on runoff generation in Star Creek watershed and its sub-watersheds. Specifically, 1) precipitation-runoff relationships and watershed storage were quantified; 2) timing and drivers of hydrologic connectivity were identified; and 3) source water contributions to streamflow were estimated. Multi-year precipitation patterns changed from dry (2008-2012) to wet (2013-2014) conditions and caused an increase in unit area discharge for all but one sub-watershed. Despite a change in annual flow contribution and total discharge, event-scale rainfall-runoff responses did not change. The annual snowmelt pulse saturated the landscape, created the main period of hydrologic connectivity in the watershed, and controlled the magnitude of event-scale rainfall-runoff responses. Streamflow contributions did not correlate with upslope accumulated area. Rather, the overall watershed structure, groundwater upwelling, and the distribution of snowmelt processes influenced the quantity of streamflow contributions. Two locations of subsurface storage were identified: shallow subsurface storage and bedrock storage. Shallow subsurface storage includes the soil and glacial till layers and influences event runoff, hillslope connectedness, and the carry-over of precipitation effects from fall to the next water year. Bedrock storage influences annual discharge because of the dominance of vertical percolation and groundwater recharge and high annual groundwater contribution to streamflow.
An initial displacement of old water stored in the hillslope over winter occurred at the onset of snowmelt before the stream responded significantly. This was followed by a dilution effect as the main snowmelt freshet streamflow pulse was generated by large volumes of snowmelt in the upper elevations and alpine zone. Late summer streamflow was dominated by either soil drainage or groundwater that was recharged in the alpine zone. In Star East, fall baseflows were dissimilar from all measured sources, but groundwater seep temperatures suggest that it was likely from a deeper groundwater source. This conceptualization of runoff generation can be used to anticipate how watersheds in the front-range Rocky Mountains may respond to disturbance (wildfire and logging) and climate change. These results can also be used to understand other watershed processes such as the potential sources of dissolved organic carbon and the flow pathways to the stream. -
- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.