ABSTRACT: Hydrological processes across three large middle Arctic watersheds, Boothia Penninsula, Nunuvat.

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Abstract

A hydrological processes study was undertaken across the Lord Lindsay River and major East and West Tributary watersheds (1485, 465 and 345 km2, respectively) on the Boothia Peninsula, Nunavut. Two seasons of hydrometeorological conditions were monitored across the catchments in order to characterize the scaled hydrological response of this environment to snowmelt and rainfall events. River, snow, rain and soil water was sampled throughout the season and analysed for hydrochemistry and stable isotopes in order to isolate streamflow source components and perform hydrograph separations. Records of suspended sediment concentration (SSC) were collected and, along with estimates of river discharge, were cross-correlated with meteorological variables to determine the climatic controls on streamflow and suspended sediment transport. The catchments exhibited snowmelt dominated streamflow during the spring flood period followed by a progressively dominant soil water response. The relative dominance of the snowmelt water reservoir varied between streamflow seasons as well as at different watershed scales, appearing to be considerably influenced by late winter snow cover and extent that lead to subsequent variations in contributing source area. Late season contributions from a depleted source in the East Tributary appears to demonstrate the importance of persistent snow banks to streamflow and suggests a relatively limited contributing area at the watershed scale (c. 300 km2). Snow and soil water survey results showed considerable variability both at a spatial and inter-annual scales, further emphasing the challenges of obtaining conservative and representative end member values for hydrograph separation. Substantive suspended sediment transfer occurred only during the short-lived nival peak and the duration of the peak appears to be broadly scaled with intra-annual catchment snow water equivalence (SWE). Thermal energy was critical for initially generating streamflow and suspended sediment transfer, but only until watershed snowpack had been largely exhausted. Thus, total annual suspended sediment load in this environment is ultimately a function of total discharge through SWE rather than a function of melt energy. Specific sediment yields were some of the lowest recorded in the arctic, ranging between 0.2 to 1.9 t·km-2·a-1. The dynamics of river response at the large scale are poorly understood as past research has focused predominantly on small watersheds and primary processes. Furthermore, hydrological research has for the most part been restricted to low and high arctic catchments, while investigations in middle arctic regions have been limited. This project serves to improve the understanding of the hydrological response of middle arctic watersheds of different scales in order to determine the sensitivity of these environments to climate change and make inferences of past and future hydrological conditions.

Bibliography of Canadian Geomorphology