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Personne :
Lemieux, Jean-Michel

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Lemieux

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Jean-Michel

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Université Laval. Département de géologie et de génie géologique

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ncf11850011

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Résultats de recherche

Voici les éléments 1 - 9 sur 9
  • PublicationRestreint
    Groundwater 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.
  • PublicationAccès libre
    Development of a long term monitoring network of sensitive clay slopes in Québec in the context of climate change
    (springer international publishing, 2017-05-24) Locat, Pascal; Cloutier, Catherine; Locat, Ariane; Fortin, Alexis; Lemieux, Jean-Michel; Locat, Jacques; Leroueil, Serge; Demers, Denis; Bilodeau, Chantal
    The Government of Québec recently initiated the deployment of a vast groundwater pressures monitoring network in postglacial marine clays to document their variations in time and improve our understanding of the relationship between failure initiation and climate in clay slopes. This project aims at evaluating the impacts of climate change on clay-slope stability and how it can be integrated in landslide risk management to improve public safety. Hydrogeological data will be acquired at sites located throughout the Québec Province’s post-glacial clay deposits to create a public georeferenced index of typical hydrogeological conditions. The project goes beyond the characterization of groundwater pressures and their variations in clay slopes. Indeed, slope deformation will be measured at several sites. Also, two sites in flat terrain will be instrumented in order to evaluate mechanical properties of clay layers in simple 1-D conditions and groundwater recharge. The unsaturated clay crust in slopes susceptible to superficial landslides will be characterized and instrumented. The current lifetime of the monitoring project has been set to a period of 25 years.
  • PublicationRestreint
    Integrated hydrological modeling of climate change impacts in a snow-influenced catchment
    (Water Well Journal Pub. Co., 2018-11-19) Therrien, René; Lemieux, Jean-Michel; Cochand, Fabien
    The potential impact of climate change on water resources has been intensively studied for different regions and climates across the world. In regions where winter processes such as snowfall and melting play a significant role, anticipated changes in temperature might significantly affect hydrological systems. To address this impact, modifications have been made to the fully integrated surface-subsurface flow model HydroGeoSphere (HGS) to allow the simulation of snow accumulation and melting. The modified HGS model was used to assess the potential impact of climate change on surface and subsurface flow in the Saint-Charles River catchment, Quebec (Canada) for the period 2070 to 2100. The model was first developed and calibrated to reproduce observed streamflow and hydraulic heads for current climate conditions. The calibrated model was then used with three different climate scenarios to simulate surface flow and groundwater dynamics for the 2070 to 2100 period. Winter stream discharges are predicted to increase by about 80, 120, and 150% for the three scenarios due to warmer winters, leading to more liquid precipitation and more snowmelt. Conversely, the summer stream discharges are predicted to fall by about 10, 15, and 20% due to an increase in evapotranspiration. However, the annual mean stream discharge should remain stable (±0.1 m3/s). The predicted increase in hydraulic heads in winter may reach 15 m and the maximum decrease in summer may reach 3 m. Simulations show that winter processes play a key role in the seasonal modifications anticipated for surface and subsurface flow dynamics.
  • PublicationRestreint
    Controls on permafrost thaw in a coupled groundwater flow and heat transport system : Iqaluit Airport, Nunavut, Canada
    (Springer, 2016-12-22) Shojae Ghias, Masoumeh; Therrien, René; Lemieux, Jean-Michel; Molson, John W. H.
    Numerical simulations of groundwater flow and heat transport are used to provide insight into the interaction between shallow groundwater flow and thermal dynamics related to permafrost thaw and thaw settlement at the Iqaluit Airport taxiway, Nunavut, Canada. A conceptual model is first developed for the site and a corresponding two-dimensional numerical model is calibrated to the observed ground temperatures. Future climate-warming impacts on the thermal regime and flow system are then simulated based on climate scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). Under climate warming, surface snow cover is identified as the leading factor affecting permafrost degradation, including its role in increasing the sensitivity of permafrost degradation to changes in various hydrogeological factors. In this case, advective heat transport plays a relatively minor, but non-negligible, role compared to conductive heat transport, due to the significant extent of low-permeability soil close to surface. Conductive heat transport, which is strongly affected by the surface snow layer, controls the release of unfrozen water and the depth of the active layer as well as the magnitude of thaw settlement and frost heave. Under the warmest climate-warming scenario with an average annual temperature increase of 3.23 °C for the period of 2011–2100, the simulations suggest that the maximum depth of the active layer will increase from 2 m in 2012 to 8.8 m in 2100 and, over the same time period, thaw settlement along the airport taxiway will increase from 0.11 m to at least 0.17 m.
  • PublicationAccès libre
    Simulating the impact of climate change on the groundwater resources of the Magdalen Islands, Québec, Canada
    (Elsevier B.V., 2015-03-01) Therrien, Pierre; Hassaoui, Jalil; Ouellet, Michel; Therrien, René; Lemieux, Jean-Michel; Molson, John W. H.
    Study region This study is conducted in the Magdalen Islands (Québec, Canada), a small archipelago located in the Gulf of St. Lawrence. Study focus This work was undertaken to support the design of a long-term groundwater monitoring network and for the sustainable management of groundwater resources. This study relies mostly on the compilation of existing data, but additional field work has also been carried out, allowing for the first time in the Magdalen Islands, direct observation of the depth and shape of the transition zone between freshwater and seawater under natural conditions. Simulations were conducted along a 2D cross-section on Grande Entrée Island in order to assess the individual and combined impacts of sea-level rise, coastal erosion and decreased groundwater recharge on the position of the saltwater–freshwater interface. The simulations were performed considering variable-density flow and solute transport under saturated-unsaturated conditions. The model was driven by observed and projected climate change scenarios to 2040 for the Magdalen Islands. New hydrological insights for the region The simulation results show that among the three impacts considered, the most important is sea-level rise, followed by decreasing groundwater recharge and coastal erosion. When combined, these impacts cause the saltwater–freshwater interface to migrate inland over a distance of 37 m and to rise by 6.5 m near the coast to 3.1 m further inland, over a 28-year period.
  • PublicationAccès libre
    A conceptual model for anticipating the impact of landscape evolution on groundwater recharge in degrading permafrost environments
    (American Geophysical Union, 2020-05-12) Young, Nathan Lee; Delottier, Hugo; Lemieux, Jean-Michel; Fortier, Richard; Fortier, Philippe
    Temperatures in the arctic and subarctic are rising at more than twice the rate of the global average, driving the accelerated thawing of permafrost across the region. The impacts of permafrost degradation have been studied in the discontinuous permafrost zone at Umiujaq, in northern Quebec, Canada, for over 30 years, but the effects of changing land cover on groundwater recharge is not well understood. The water table fluctuation method was used to compute groundwater recharge using four years of water level data and soil moisture readings from five field sites characteristic of different stages of permafrost degradation and vegetation invasion. Results indicate that as vegetation grows taller, groundwater recharge increases, likely due to increased snow thickness. Results were then combined with a preexisting conceptual model that describes the evolution from tundra to shrubland and forests to create a new model for describing how groundwater recharge is affected by landscape evolution.
  • PublicationRestreint
    Groundwater 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.
  • PublicationRestreint
    Development of a three-dimensional geological model, based on Quaternary chronology, geological mapping, and geophysical investigation, of a watershed in the discontinuous permafrost zone near Umiujaq (Nunavik, Canada)
    (Springer, 2020-02-27) Ouellet, Michel; Therrien, René; Banville, David-Roy; Lemieux, Jean-Michel; Fortier, Richard; Lévesque, Richard; Molson, John W. H.
    Among the few positive impacts of climate warming in cold regions, permafrost degradation can increase the availability of groundwater as a potential source of drinking water for northern communities. Near the Inuit community of Umiujaq in Nunavik, Canada, a watershed in a valley in the discontinuous permafrost zone was instrumented to monitor the impacts of climate change on permafrost and groundwater, and assess the groundwater availability and quality. Based on Quaternary chronology, knowledge of periglacial processes, and an investigation carried out in the valley (including mapping of Quaternary deposits and icerich permafrost distribution, drilling and sampling of deposits, and geophysical surveys), a three-dimensional (3D) geological model of the watershed was built into GoCAD to assess the hydrogeological context in this degrading permafrost environment. In total, six units were identified within the watershed including an upper aquifer in marine sediments, a lower aquifer at depth in glaciofluvial and glacial sediments, and the bedrock acting as a low-permeability boundary. An aquitard, made of frostsusceptible silty sand and discontinuously invaded by ice-rich permafrost, confines the lower aquifer. This 3D geological model clarifies the local stratigraphic architecture and geometries of Quaternary deposits, especially the stratigraphic relationship between the two aquifers, aquitard, and bedrock, and the extent of ice-rich permafrost within the watershed. It is the cornerstone to understand the groundwater dynamics within the watershed and to carry out numerical modelling of coupled groundwater flow and heat transfer processes to predict the impacts of climate change on groundwater resources in this degrading permafrost environment.
  • PublicationAccès libre
    Numerical simulations of shallow groundwater flow and heat transport in a continuous permafrost setting under the impact of climate warming
    (Conseil national de recherches du Canada, 2018-06-11) Shojae Ghias, Masoumeh; Therrien, René; Lemieux, Jean-Michel; Molson, John W. H.
    Numerical simulations of coupled groundwater flow and heat transport are used to address how hydrogeological conditions can affect permafrost dynamics. The simulations are based on a 2D vertical-plane conceptual model of a study site at the Iqaluit Airport, Nunavut, Canada, which includes a 50 m deep permafrost terrain with a shallow active layer, overlain by a paved taxiway with winter snow-covered embankments. Coupled groundwater flow and advective-conductive heat transport with freeze-thaw dynamics, temperature-dependent porewater freezing functions and latent heat are included in the model. The simulation results show that a smooth (low-slope) freezing function with a higher residual unfrozen moisture content produced a deeper thaw front compared to that using a steeper freezing function, generating a maximum increase in the depth to permafrost of 17.5 m after 268 years. Permafrost thaw rates in high-permeability zones within a heterogeneous system were also relatively higher compared to an otherwise equivalent homogeneous soil, resulting in a maximum increase of 2.6 m in the depth to permafrost after 238 years. As recharge water cools while flowing along the upgradient permafrost table, advectively driven heat transport is paradoxically shown to temporarily increase the height of the permafrost table in downgradient areas.