Assessment of hydrological baseline condition and its alteration in Athabasca River Basin, Canada

Abstract

Study regionAthabasca River Basin (ARB), Canada. Study focusThis study aimed to characterize the flow regime of the ARB, a basin with diverse hydroclimatic and geological characteristics. Forty-two different flow indicators from the Indicators of Hydrological Alteration (IHA) and Cold regions Hydrological Indicators of Change (CHIC) were employed. The natural range of these indicators was established for the baseline period (1961–1990), and subsequent alterations during the recent period (1991–2020) were systematically examined. Principal Component Analysis (PCA) was applied to identify pivotal indicators shaping the basin's flow regime. In addition, trends of key indicators were examined at eight distinct locations within the basin. New hydrological insights for the study regionThe findings indicate spatiotemporal variation between the basin's upper and lower parts. The upstream region exhibited an earlier peak flow (9 days), an earlier ice break-up (17 days), and a shorter ice cover duration (22 days) compared to the downstream region. Increased winter and spring flow have led to an augmentation of annual flow by 3.8 % in the upper region. In contrast, downstream flow experienced a decline throughout the year (11.38 %), which was found to be statistically significant at a rate of 3.24 m3/s/year. Alteration analysis revealed a shift toward the 'low category' (below their defined baseline range) for most indicators in the recent period, underscoring a transition towards a diminishing flow regime, with an overall alteration ranging at low to moderate levels (19–38 %). Late summer flow reduction (8–25 %) can have critical implications, given the rising water demand in the basin. The study identified eleven key indicators encapsulating the basin's flow regime variability range. It was found that ice cover, its break-up, and spring freshet significantly influence the flow regime of the basin. The findings from this study will assist decision-makers in making more informed decisions for the holistic management of water resources in the basin.