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Gabriel Chiasson-Poirier

 

Master student

Department of geography, Université de Montréal

520, ch. de la Côte-Sainte-Catherine Building
520, ch. de la Côte-Sainte-Catherine
Université de Montréal
Quebec, Canada

8198292954
gchiassonpoirier@hotmail.ca

 

 


 

Direction

 
 

Research project

Hydrogeomorphic controls and shallow groundwater flow patterns during the arctic summer, Niaqunguk River watershed, Iqaluit, Nunavut

CONTEXT
Climate change is impacting the hydrology of northern rivers. Recent studies suggest that Arctic warming and associated permafrost degradation are contributing to a widespread upward trend in minimum daily flows (Smith et al. 2007, St-Jacques & Sauchyn 2009). Understanding the link between permafrost thaw and altered flow regimes requires fundamental knowledge of the processes controlling the flow and storage of water within the seasonally thawed soils above permafrost (i.e., active layer) (Chiasson-Poirier 2016). However, few field studies have investigated the movement of water within the active layer. Better knowledge of active layer processes is critical to our understanding of the impact of climate change on the hydrology, geochemistry, and ecology of northern rivers; and on the delivery of water, nutrients, sediments and carbon to the Arctic Ocean.

OBJECTIVES
The aim of my research is to provide a better characterization of how geomorphic features of the arctic landscape can influence subsurface flow patterns and thus their connectivity with surface water during the arctic summer.
To realize this goal, I will:

  1. track across a hillslope the evolution of suprapermafrost groundwater flow patterns and frost table topography;
  2. identify which are the dominant physical controls governing the routing of shallow groundwater flow during the thawing period and relate these controls to different degrees of hydrological connectivity;
  3. assess the importance of groundwater contributions relative to other water sources (rain, lakes, overland flow) that contribute to the flow of a tributary stream at the foot of the studied hillslope to confirm the magnitude of hydrological connectivity across the hillslope-stream sequence.

STUDY SITE AND METHODOLOGY
Field studies will take place in a subwatershed (0.41km2) centrally located within the 58km2 Niaqunguk River watershed, located northeast of Iqaluit, NU (63° 45’ N, 68° 33’ W). This subwatershed is characterized by a wide range of surficial deposits types and a shallow active layer (<1.5m) (Leblanc et al. 2015). The surficial deposit types (i.e., glaciofluvial, boulder fields, organic and till cover of varying thickness) present within this subwatershed are representative of those throughout the Niaqunguk watershed.

Fieldwork will involve:

  1. continuous monitoring of the flow network across a hillslope-stream toposequence using piezometers equipped with water level sensor-loggers and a mapping of the three-dimensional architecture of the hillslope using both intrusive (e.g., soil cores, depth to frost table measurements) and non-intrusive methods (e.g., electrical resistivity surveys);
  2. source water characterization (i.e., groundwater, stream, lake and rainfall) using environmental tracers (e.g., electrical conductivity, stable water isotopes, and Dissolve Organic Carbone (DOC).

Combined canonical and asymmetric eigenfunction analysis will be used to determine which geomorphological features of the hillslope and degree of hydrological connectivity better explained le variation in groundwater flow patterns observed through the summer. Hydrochemical analysis will then be used to quantify the proportion of groundwater contributing to streamflow and to track the evolution of structural connectivity during the thaw season. Additionally, I will complete a detailed characterization of the surficial geology of the subwatershed to assess how distinct deposit-type and hydrogeomorphic features influence hydrological connectivity.

IMPLICATIONS
The knowledge gathered by this study is critical to project the response of arctic river systems to climate change. Outcomes will contribute to fundamental hydrological knowledge and will also be particularly relevant in the context of the Niaqunguk River watershed, as the rapidly expanding City of Iqaluit has identified the river as a supplemental potable water source. A better understanding of groundwater contributions to river discharges are necessary for a more effective management of this critical water resource.

 
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