Personne : Cochand, Marion
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Centre d'études nordiques, Université Laval
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- PublicationRestreintDirect measurement of groundwater flux in aquifers within the discontinuous permafrost zone: an application of the finite volume point dilution method near Umiujaq (Nunavik, Canada)(Springer, 2020-01-29) Jamin, Pierre; Cochand, Marion; Lemieux, Jean-Michel; Dagenais, Sophie; Fortier, Richard; Brouyère, Serge; Molson, John W. H.Permafrost thaw is a complex process resulting from interactions between the atmosphere, soil, water and vegetation. Although advective heat transport by groundwater at depth likely plays a significant role in permafrost dynamics at many sites, there is lack of direct measurements of groundwater flow patterns and fluxes in such cold-region environments. Here, the finite volume point dilution method (FVPDM) is used to measure in-situ groundwater fluxes in two sandy aquifers in the discontinuous permafrost zone, within a small watershed near Umiujaq, Nunavik (Quebec), Canada. The FVPDM theory is first reviewed, then results from four FVPDM tests are presented: one test in a shallow supra-permafrost aquifer, and three in a deeper subpermafrost aquifer. Apparent Darcy fluxes derived from the FVPDM tests varied from 0.5 × 10−5 to 1.0 × 10−5 m/s, implying that advective heat transport from groundwater flow could be contributing to rapid permafrost thaw at this site. In providing estimates of the Darcy fluxes at the local scale of the well screens, the approach offers more accurate and direct measurements over indirect estimates using Darcy’s law. The tests show that this method can be successfully used in remote areas and with limited resources. Recommendations for optimizing the test protocol are proposed.
- PublicationRestreintRapid groundwater recharge dynamics determined from hydrogeochemical and isotope data in a small permafrost watershed near Umiujaq (Nunavik, Canada)(Springer, 2020-01-25) Cochand, Marion; Barth, Johannes (Johannes A. C.); Therrien, René; Geldern, Robert van; Lemieux, Jean-Michel; Fortier, Richard; Molson, John W. H.Hydrogeochemical data are used to better understand recharge dynamics and to support a hydrogeological conceptual model in a 2-km2 watershed in a discontinuous permafrost zone in Nunavik, Canada. The watershed contains an upper (surficial) and lower aquifer within Quaternary deposits, above and below a marine silt layer containing ice-rich permafrost mounds. The analysis is based on water samples from precipitation, groundwater monitoring wells, ground ice in permafrost mounds, thermokarst lakes and a perennial stream. Groundwater geochemistry in both aquifers reflects young, poorly evolved waters, with mainly Ca-HCO3 water types and low mineralisation ranging from 11 to 158 mg/L total dissolved solids (TDS), implying short pathways and rapid travel times of a year or less. While relatively low, TDS signatures in groundwater and surface water show increasing values downgradient. Groundwater isotope values (δ18OH2O and δ2HH2O) are often strongly influenced by snowmelt, while those of thermokarst lakes show evidence of evaporation. Recharge along the cuesta contributes to a transverse component of groundwater flow within the valley with higher TDS and δ13CDIC values influenced by open-system weathering. Even where permafrost-free, the marine silt unit has a strong confining effect and plays a more important role on recharge dynamics than the discontinuous permafrost. Nevertheless, the vulnerability of these types of hydrogeological aquifer systems is expected to increase due to rapid recharge dynamics associated with the gradual loss of the confining effect of permafrost. This hydrogeochemical data set will be useful as a baseline to document impacts of permafrost degradation on the hydrogeological system.
- PublicationAccès libreÉtude hydrogéochimique des eaux souterraines dans un environnement pergélisolé en voie de dégradation, Umiujaq, Nunavik, Québec(2019) Cochand, Marion; Lemieux, Jean-Michel; Barth, JohannesLes effets des changements climatiques sont particulièrement importants dans les régions arctiques et subarctiques. L’augmentation de la température de l’atmosphère entraine notamment le réchauffement du pergélisol qui perd en épaisseur et en couverture spatiale. Cette dégradation a des conséquences sur les écosystèmes, le paysage, la stabilité des sols, des bâtiments et des infrastructures ainsi que sur les populations locales et sur leur mode de vie. La dégradation du pergélisol conduira probablement à la perte de la couche confinante formée par le pergélisol favorisant ainsi la recharge des aquifères et modifiant les interactions entre les eaux de surface et les eaux souterraines. Cependant, l’impact de cette dégradation sur la qualité et la disponibilité des eaux souterraines demeure en grande partie inconnu. Cette thèse a été motivée par le manque d’informations sur les eaux souterraines en région de pergélisol discontinu, par les changements environnementaux rapides liés au réchauffement climatique et par le potentiel de l’eau souterraine comme ressource en eau potable pour, entre autres, les communautés du Nunavik (Québec, Canada). Ce projet se concentre sur la compréhension des écoulements et sur la qualité de l’eau souterraine dans la vallée de Tasiapik, un petit bassin versant en zone de pergélisol discontinu proche d’Umiujaq au Nunavik. Cette étude se base sur une analyse approfondie de l’hydrogéochimie des eaux souterraines, des eaux de surface, des précipitations et du pergélisol riche en glace. Cette thèse est divisée en deux parties. La première partie (chapitre 2) est une revue de la littérature scientifique existante sur l’hydrogéochimie des eaux souterraines. La seconde partie (chapitre 3) présente l’étude hydrogéochimique des eaux souterraines dans la vallée de Tasiapik. Cette thèse est complétée par une introduction générale (chapitre 1), une synthèse (chapitre 4) et une conclusion (chapitre 5).
- PublicationRestreintGroundwater hydrogeochemistry in permafrost regions(Wiley, 2019-04-25) Cochand, Marion; Lemieux, Jean-Michel; Molson, John W. H.This review paper provides a summary of the current state of knowledge regarding groundwater hydrogeochemistry in permafrost regions and presents expected impacts of permafrost degradation on groundwater quality. Using published case studies, the most practical monitoring approaches are reviewed, possible monitoring issues are highlighted, and links between groundwater chemistry signatures and associated flow systems in northern climates are identified. Hydrogeochemical characteristics of groundwater in permafrost regions depend on the same reactions as in nonpermafrost regions, but in acting as a confining layer, permafrost can affect groundwater chemistry by restricting recharge and limiting exchange of energy and mass between the ground surface, surface water and groundwater. Rock (mineral)–water interactions can also increase due to longer residence times. The impacts of climate change on groundwater quality in permafrost regions are thought to be linked to the loss of this confining layer. Various studies have reported significant modifications in shallow and deep groundwater contributions to surface water, marked by a decrease in dissolved organic carbon and an increase in total dissolved solids in stream water linked to declining permafrost coverage. Future studies related to hydrogeology in permafrost areas should include better in situ hydrogeochemical characterization of groundwater to assess its potential for future use as the climate warms.
- PublicationRestreintGroundwater occurrence in cold environements : examples from Nunavik, Canada(Springer, 2016-04-19) Cochand, Marion; Ouellet, Michel; Therrien, René; Talbot Poulin, Marie-Catherine; Murray, Renaud; Banville, David-Roy; Lemieux, Jean-Michel; Fortier, Richard; Molson, John W. H.Water availability and management issues related to the supply of drinking water in northern communities are problematic in Canada. While rivers and lakes are abundant, they are vulnerable to contamination and may become dry in winter due to freezing. Groundwater can often provide a more secure and sustainable water source, however its availability is limited in northern Canada due to the presence of permafrost. Moreover, the exploitation of northern aquifers poses a dual challenge of identifying not only permafrost-free areas, but also permeable areas which will allow groundwater recharge and exploitation. Suitable aquifers are not as common in northern Canada since the shallow subsurface is mostly composed of low-permeability crystalline rocks or unconsolidated sediments of glacial origin that are highly heterogeneous. In order to investigate groundwater occurrence and associated geological contexts in Nunavik (northern Quebec, Canada), along with exploring how these resources will evolve in response to climate change, field and compilation work were conducted in the surroundings of the four villages of Salluit, Kuujjuaq, Umiujaq and Whapmagoostui-Kuujjuarapik. These villages are located in different permafrost zones, ranging from continuous to discontinuous, as well as in different geological environments. It was found that despite the ubiquitous presence of permafrost, unfrozen aquifers could be identified, which suggests that groundwater may be available as a source of drinking water for small communities. Expected climate change, with predicted permafrost thawing and increases in temperature and precipitation, should enhance groundwater availability and may contribute to a more secure source of drinking water for northern communities.
- PublicationAccès libreGroundwater dynamics within a watershed in the discontinuous permafrost zone near Umiujaq (Nunavik, Canada)(Springer, 2020-02-08) Parhizkar, Masoumeh; Delottier, Hugo; Cochand, Marion; Therrien, René; Murray, Renaud; Lemieux, Jean-Michel; Dagenais, Sophie; Pryet, Alexandre; Fortier, Richard; Molson, John W. H.Groundwater distribution and flow dynamics were studied in a small watershed located in the discontinuous permafrost zone near Umiujaq in Nunavik (Québec), Canada, to assess the seasonal variations and perform a quantitative analysis of the water cycle in a subarctic watershed. Due to the complexity of the subsurface geology within the watershed, an integrated investigation was instrumental to provide a detailed understanding of the hydrogeological context as a basis for the water balance. Based on this water balance, for the two studied hydrological years of 2015 and 2016, the average values are 828 mm for precipitation, 337 mm for evapotranspiration, 46 mm for snow sublimation, 263 mm for runoff, 183 mm for groundwater exchange (losses with other aquifers outside the watershed), and 0 mm for change in water storage. Although these values likely have significant uncertainty and spatial variability, this water balance is shown to be plausible. It was also found that permafrost influences surface water and groundwater interaction, even if located in low-permeability sediments. It is expected that permafrost degradation will likely increase stream baseflow, especially in winter.