Dynamiques hydrologiques d’un petit bassin versant arctique, rivière Niaqunguk, Iqaluit, Nunavut
Despite recent advances in the hydrological knowledge of permafrost regions, precise predictions or modelling of hydrological dynamics in Arctic watersheds remains difficult. In this master thesis a combination of field measurements, chemistry and statistical analysis were conducted at the hillslope scale and at watershed scale within the Niaqunguk River catchment, to improve our understanding of the processes controlling the water delivery to rivers in permafrost landscape. The first study show that hillslope drainage dynamics were intrinsically linked to permafrost active layer thawing patterns. The microtopography of the surficial organic layer has a great influence on the distribution across the hillslope, by first enhancing the accumulation of water in surficial depressions, which in return enhance localized thaw and the accumulation of water in subsurface depressions. The second study conducted at the watershed scale allowed to delineated, based on the particularities of the water chemistry along the river network, four distinct periods, corresponding respectively to early snowmelt, snowmelt recession, baseflow and summer rainfall events. Since dominant hydrological processes within the watershed changed from one period to another, this period division is relevant the understand the behaviour of the river system. The primary processes associated with each of the four periods were: snowmelt contributions, the distinction between late lying snowpack melt and lake contributions, subsurface flows through mineral deposits and surface flows through the organic layer. Fundamental hydrological knowledge generated in this research will greatly help to improve our ability to predict the response of Arctic hydrological systems to climate changes, but is also indispensable for a sustainable management of a future exploitation of the Niaqunguk River as a potable water for the City of Iqaluit.
hydrologie Arctic hydrology active layer subsurface flows lakes surface flows