Étude spatiotemporelle de la qualité de l'eau souterraine sur l'aire d'alimentation d'un captage municipal en milieu agricole

Authors: Bonton, Alexandre
Advisor: Bouchard, Christian
Abstract: A sound scientific basis for decision-making about land management and groundwater protection includes a proper understanding of the relationships between agricultural activities and the quality of pumped water at a municipal well. There is a need to assess both nitrate and bacterial contamination in a capture area, and to ensure that regulations through protection areas are adapted to prevent risks to consumer health. For this purpose, field monitoring and numerical simulations were performed on the actual case of a municipal well in an agricultural area in the province of Québec (Canada). A number of 38 piezometers were installed within the capture area in order to monitor physico-chemical and bacteriological parameters in groundwater. At the same time, a three-dimensional Water flow and Nitrate transport Global Model (WNGM) in unconfined aquifer was developed in order to simulate nitrate concentrations in the aquifer and in the municipal well, in relation with agricultural practice. Model calibration was performed using water level and nitrate concentration measured in the aquifer. The simulations of several scenarios provided a better understanding of past trends of nitrate concentrations in the municipal well, as well as predictions of nitrate concentrations in the municipal well assuming different land management practices within the capture area. The results of physico-chemical monitoring demonstrate the impact of agricultural activities on groundwater quality, particularly on nitrate levels. The results of bacteriological monitoring show a significant variability of bacteria content in groundwater. Finally, the results of the numerical simulation demonstrate that modelling is able to provide valid and useful prediction of nitrate levels in the municipal well, and that better agricultural practice can improve significantly groundwater quality at the well.
Document Type: Thèse de doctorat
Issue Date: 2010
Open Access Date: 16 April 2018
Permalink: http://hdl.handle.net/20.500.11794/21333
Grantor: Université Laval
Collection:Thèses et mémoires

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