Permafrost thaw-induced forest to wetland conversion: potential impacts on snowmelt and basin runoff in northwestern Canada

• Main Author: Haughton, Emily
• Format: Text
• Language: English
• Published: Scholars Commons @ Laurier 2018
• Subjects: hydrology; permafrost; snowmelt; SWE; Other Environmental Sciences; Water Resource Management; Canada; Northwest Territories; Peat
• Online Access: https://scholars.wlu.ca/etd/2022; https://scholars.wlu.ca/context/etd/article/3135/viewcontent/auto_convert.pdf

In the discontinuous permafrost zone of northwestern Canada, snow covers the ground surface for over half the year, thus snowmelt constitutes a primary source of ecosystem moisture supply and strongly influences stream hydrographs. The peat landscapes along the southern limit of discontinuous permafrost are dominated by forested permafrost plateaus (“forest”), and treeless, permafrost-free wetlands (“wetland”). Permafrost-thaw induced transformation of this landscape has changed water flow and storage processes and therefore introduced new uncertainties on the region’s water futures. Here, I a) characterize forest and wetland water storage and flow from snowmelt, and b) evaluate how permafrost thaw-induced wetland expansion at the expense of forest might affect the proportion of snowmelt that can contribute to basin runoff during the spring freshet of a 152-km2 watershed in the southern Northwest Territories. Analysis of historical imagery suggests that wetland coverage within a 0.14-km2 area-of-interest increased by approximately 7 % between 1977 and 2010. Over the 34-year period, total areal SWE decreased by 1.5 %, but the amount of SWE made available as runoff increased by 25%. The increased proportion of the snow cover that contributes melt water to streams may be a factor contributing to the rising steam flows observed across the study region in the mid-1990s and early 2000s, given that there has been no concomitant increase in winter-time precipitation.