No 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

No abstract

Located south of Quebec City, the Chaudière River Watershed encompasses an area of 6700 km2, from the American border to the St. Lawrence River. It is mainly agricultural region where approximately 65% of the population relies on groundwater for its main source of water. The regional aquifer consists of fractured rocks of the Appalachian geological province and sparse coarse surficial sediments. This poster presents results of a regional hydrogeological study focusing on the development of a conceptual model for the regional groundwater flow. Estimated average recharge rates is 64 mm for fractured bedrock and 273 mm for coarse sediments. Over 600 measurements of groundwater levels show a close correlation with topography. The mean hydraulic conductivity of the bedrock is relatively low (K=1x10-7 m/s), suggesting mainly local groundwater flow. Chemical analyses of 155 groundwater samples show that groundwater is of good quality relative to the drinking water standards.