Landscape and Hydrological Controls on Organic Matter and Surface Water Chemistry in the Niaqunguk (Apex) River Watershed, Nunavut
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Authors
Nguyen, Lee
Date
2025-05-02
Type
thesis
Language
eng
Keyword
water chemistry , Organic matter , Arctic river , Watershed processes
Alternative Title
Abstract
Anthropogenic warming in the Arctic is causing shifts in hydrological cycling and permafrost thaw, with implications for water quality and availability in northern communities. In the capital of the Canadian Territory Nunavut, the city of Iqaluit reports declining water levels, further evidence of the challenges many northern and Indigenous communities face in accessing clean, potable water. The Niaqunguk (or commonly known as Apex) River watershed (63° 45' 20" N, 68° 27' 37" W) has been selected to supplement the city’s main reservoir, Lake Geraldine. However, it is uncertain how the water quality of the river will change with further warming. The objectives of this research were to 1) investigate the landscape controls on spatial and temporal stream water chemistry trends and 2) determine the factors influencing dissolved organic matter (DOM) composition and quality.
To address these research objectives, stream water samples and discharge measurements were collected several times weekly at three sub-catchments of varying dominant surficial geologies and three sites at the main stem during the warm period (Jun – Aug 2022). Stable water isotope signatures, major ion concentrations, dissolved organic carbon (DOC), total dissolved nitrogen (TN), and DOM absorbance and fluorescence properties were derived from these samples. The rise in geogenic (Ca2+, Mg2+, SO42–, and HCO3–) solutes over the study period suggests enhanced subsurface flows contributing to stream water chemistry. Further, the spring freshet is a significant driver of DOC and terrestrial DOM export. The decline in fluorescence intensity downstream and over the study period indicates photodegradation or microbial decomposition of fluorescent DOM. The results from this study indicate this watershed will be sensitive to changes in the permafrost under a warming climate, with implications for increases in solute and inorganic nutrient export as consequence of permafrost thaw. These results improve our understanding of the controls on stream water chemistry in Arctic catchments, which is critical for strengthening community resilience and adaptation capacity with regards to climate change.
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Attribution-NoDerivatives 4.0 International