ABSTRACT: Hydrology of two Hillslope Streams, Polar Bear Pass, Nunavut, Canada.

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Abstract

Polar Bear Pass (PBP) is a large low-gradient wetland which spans east-west across the central part of Bathurst Island, in the Canadian High Arctic (75o44'N, 98o25'W). It is about 20 km long and about 4 km wide, dotted by ponds, two large lakes and is bordered by low-lying hills with an elevation of about 90 m. Valleys and incised streams ranging from single order to higher dissect the hills and act to channel meltwater, rainwater and nutrients into the low-lying wetland. While the biology of PBP is well known, its hydrology and future sustainability in response to climate warming is not clear. In 2007, we investigated the hydrology of channel snow in a single-order stream near base camp and in 2008; we expanded our study to include a 2nd order hillslope stream. In this study, we investigate the seasonal hydrology of two hillslope streams (small-0.2 km2, large-4.2 km2) from the end of winter to freeze-back. Eventually, we want to assess the importance of these lateral water sources in the resilience of this High Arctic wetland. Snowcover was thin in 2008 but summer precipitation was higher than normal for this polar desert environment (> 90 mm). Air temperatures were lower than in 2007 but above average for the area. The two hillslope watersheds depict nival regimes where snowmelt is a major component of the streamflow pattern, with diurnal pulses driven by meteorologic conditions (e.g. radiation receipt, Ta > 0oC). In the post- snowmelt period, streamflow was maintained in the large basin but not in the smaller one. The large basin had zones within its tributaries with thick organic material, ground ice and thin frost tables (ca. 0.40 m), which likely limited infiltration and water storage, prolonging streamflow. The small basin was largely devoid of vegetation and had a deep frost table (ca. 0.7 m). Streamflow did not occur until basin storage (e.g. soil moisture) was satisfied. Consequently, seasonal water budgets and runoff ratios for the two hillslope watersheds were different. This study suggests that in the post-snowmelt period, basin characteristics (soils, vegetation, and ground ice) and their location in a hillslope stream network can play an important role in prolonging either flow, or limiting streamflow through absorption and storage of water. t

Bibliography of Canadian Geomorphology