Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Geography & Environmental Studies

Faculty/School

Faculty of Arts

First Advisor

William Quinton

Advisor Role

Thesis Supervisor

Abstract

Permafrost degradation in the peat-rich southern fringe of the discontinuous permafrost zone is producing substantial changes to land cover with concomitant expansion of permafrost-free wetlands (bogs and fens) and shrinkage of forest supported by permafrost peat plateaus. Predicting discharge from headwater basins in this region depends on understanding and numerically representing the interactions between storage and discharge within and between the major land cover types, and how these interactions are changing. To better understand the implications of land cover change on wetland discharge, the hydrological behaviour of a channel fen in the headwaters of Scotty Creek, Northwest Territories, Canada, dominated by peat plateau-bog complexes, was modelled using the Cold Regions Hydrological Modelling platform for the period of 2009 to 2015. The model performance was evaluated against measured snow depth, snow water equivalent (SWE), evapotranspiration (ET), and water level. The model adequately simulated snowpack dynamics, with root mean square errors (rmse) not greater than 11.8 cm for hourly snow depth at a point and 37 mm for annual maximum SWE from snow survey transects. The model generally captured seasonal ET flux and water level fluctuation, with rmse less than 0.089 mm/hr and 50 mm, respectively. After model performance evaluation, a sensitivity analysis was conducted to assess the consequences of permafrost loss on discharge from the sub-basin by incrementally reducing the ratio of peat plateau to wetland area in the modelled sub-basin. Reductions in permafrost extent decreased total annual discharge from the channel fen by 2.5% on average for every 10% permafrost loss, due to increased surface storage capacity, reduced runoff efficiency and increased landscape ET. Runoff ratios for the fen hydrological response unit dropped from 0.54 to 0.48 after the simulated 50% permafrost area loss, with a substantial reduction from 0.47 to 0.31 during the snowmelt season. The reduction in peat plateau area also resulted in decreased intra-annual variability in discharge, with higher low-flows and small increases in subsurface discharge, and decreased peak discharge with large reductions in surface runoff. The current trend of increasing discharge observed in the Scotty Creek basin may not be permanent, as this model shows that a completely connected sub-basin results in decreasing channel fen discharge with further land cover change.

Convocation Year

2018

Convocation Season

Spring

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Hydrology Commons

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