| Summary: | The objective of this thesis is to quantify seasonal source water contributions to the Athabasca River in Alberta Canada. A secondary objective was to evaluate a novel method for reconstructing the isotopic composition of streamflow over the ice-on period and utilize this data to quantify source water contributions to winter streamflow. Quantifying source water contributions to streamflow is important because the Athabasca is a large, snow-dominated catchment where climate change is expected to impact the quantity and timing of source waters. The water resources in the Athabasca River Basin (ARB) are essential in supporting communities, the economy and ecosystems in the province of Alberta. This includes water needs of municipalities, oil sands operations and sensitive ecosystems, such as the Peace Athabasca Delta, an internationally recognized protected area. While the lower reaches of the Athabasca has been the subject of many studies, stable water isotope analysis has been limited in the upper portion of the ARB leaving a knowledge gap around existing snow and glacial melt water resources. This research focuses on the Upper and Middle reaches of the Athabasca and includes a subset of data for the McLeod catchment, which is nestled in the Middle Athabasca. To assess source water contributions three synoptic studies were undertaken to collect stable water isotope samples over a hydrological year from August 2016 to August 2017. This dataset was supplemented by winter streamflow data calculated using a novel method that reconstructs the isotopic composition of winter streamflow using river ice stratigraphy. The reconstruction of streamflow in the ARB produced accurate results as validated against streamflow sampling obtained over the same time period. This method also resulted ice-water fractionation values that were in alignment with the existing literature. While these results support the future use of this emerging methodology, additional studies will be required to better define the limitations to this ...
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