Groundwater Quality, Geochemical Processes and Groundwater Evolution in the Chateauguay River Watershed, Quebec, Canada

Abstract

A hydrogeochemical study was carried out in the Quebec portion of the Chateauguay River watershed. The objective was to characterize the chemical composition of groundwater in order to evaluate its quality and assess geochemical variations related to the geological and hydrogeological settings. Bulk groundwater samples were collected from 144 wells distributed evenly over the study area. Nine of the wells were sampled with a multi-level packer system, for a total of 22 multi-level samples. Groundwater shows a wide range of compositions as indicated by 12 water types defined on the basis of major ions with a weak variation of chemical composition with depth. The predominant water type, Ca-HCO 3 , occurs in most geological and hydrogeological settings. Principal Component Analysis (PCA) and geochemical graphs were used to identify the major processes that exert a control over the chemical composition of the groundwater. Approximately 80% of the geochemical variation can be explained by mixing between fresh recharge water with more saline water associated with the former Champlain Sea, which invaded the aquifer. Secondary processes are related to ion exchange and the potential dissolution of minerals. A cross-section along a major flow path shows that the geochemical evolution of groundwater leads to relations between water type groups, geochemical processes, and groundwater flow conditions. The hydrogeochemical conceptual model infers that carbonate dissolution during recharge leads to one end-member, a Ca-HCO 3 type water, which further evolves along its flow path due through ion exchange and mixing with remnant Champlain Sea water (Na-Cl), the other endmember. 504Canadian Water Resources Journal/Revue canadienne des ressources hydriques

Groundwater Recharge Assessment in the Chateauguay River Watershed

“…The Beaver Crossing esker to the east, and the Mercier esker to the west, also appear to be major recharge areas (≥250 mm). These results were also corroborated with the groundwater chemistry data, which showed elevated tritium, attesting to an important influx of recent atmospheric water (Blanchette et al, 2010). Table 5 provides recharge averages for the four major types of Quaternary sediments in the region.…”

“…In this case, the interactions between climate conditions, topography, land cover and geology are the major factors influencing the recharge rate (Cherkauer and Ansari, 2005). Several direct and indirect techniques for recharge estimation were considered, such as recharge modelling, baseflow estimation, and analyses of water table fluctuations from well hydrographs (present study); numerical modelling of the groundwater flow system (Lavigne et al, 2010); and groundwater chemical analysis (Blanchette et al, 2010). This paper focuses on the application of the Hydrological Evaluation of Landfill Performance -HELP model (Schroeder et al, 1994) for the mathematical simulation of the recharge rates.…”

Preface to the Special Issue on the Hydrogeology of the Chateauguay River Watershed

“…Lavigne et al (2010a) describe the hydraulic properties of the bedrock aquifers and present a numerical simulation of the regional groundwater flow and model calibration, while Lavigne et al (2010b) propose a methodology for estimation of the regional sustainability of the groundwater resources. Blanchette et al (2010) present the chemical composition of the groundwater, assessing its quality against the current potable water standards and describing the governing geochemical processes that impact natural groundwater quality and its evolution within the regional flow system. Giroux et al (2010) analyse the presence of pesticides in the groundwater in farmland environment.…”

Benefits and limitations of using isotope-derived groundwater travel times and major ion chemistry to validate a regional groundwater flow model: example from the Centre-du-Québec region, Canada

“…Although a complete simulation of transport processes, including dispersion and diffusion, might yield travel times that are closer to those estimated using isotopic residence time tracers (e.g., Suckow 2014;Wen et al 2016), simulated advective travel times can provide an acceptable first estimate. It is generally recognized that groundwater types are representative of flow paths (e.g., Cloutier et al 2006;Blanchette et al 2013;Saby et al 2016) and reflect, to some extent, aquifer vulnerability (Meyzonnat et al 2016). This comparison is rarely reported in the literature and should be added to model validation when data are available.…”