HR: 1340h
AN: H23B-1424    [Abstracts]
TI: Hydrogeology of a Transboundary Sandstone Aquifer, Quebec - New York
AU: Nastev, M
EM: mnastev@nrcan.gc.ca
AF: Geological Survey of Canada, 490 de la Couronne, Quebec, QC G1K 9A9 Canada
AU: Lamontagne, C
EM: charles.lamontagne@mddep.gouv.qc.ca
AF: Ministere de l'Environnement du Qu‚bec, 675 Rene Levesque Est, Quebec, QC G1R 5V7 Canada
AU: Morin, R
EM: rhmorin@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center, Denver, CO 80225 United States
AU: Williams, J
EM: jhwillia@usgs.gov
AF: U.S. Geological Survey, 425 Jordan Road, Troy, NY 12180-8349 United States
AU: Lavigne, M
EM: malavign@nrcan.gc.ca
AF: INRS-ETE, 490 de la Couronne, Qu‚bec, QC G1K 9A9 Canada
AU: * Croteau, A
EM: acroteau@inrs.ete.ca
AF: INRS-ETE, 490 de la Couronne, Qu‚bec, QC G1K 9A9 Canada
AU: Tremblay, T
EM: tremblay.tommy@courrier.uqam.ca
AF: UQAM, Centre-Ville , Montreal, QC H3C 3P8 Canada
AU: Godin, R
EM: Rejean_Godin@uqac.ca
AF: UQAC, 555 boul. Universit‚, Chicoutimi, QC G7H 2B1 Canada
AU: Dagenais, M
EM: marie-pierre.dagenais.1@ulaval.ca
AF: Universite Laval, Sainte-Foy, Quebec, QC G1K 7P4 Canada
AU: Rouleau, A
EM: Alain_Rouleau@uqac.ca
AF: UQAC, 555 boul. Universit‚, Chicoutimi, QC G7H 2B1 Canada
AB: The Potsdam sandstone aquifer of Cambrian age straddles southern Quebec and northern New York in a region known for its abundant and good quality groundwater, a resource that recently has been coveted by several bottling companies. The potential conflicts and concerns of the mainly rural and groundwater dependent population about the possible overuse of this resource has led the Quebec Ministry of Environment, Geological Survey of Canada and the U. S. Geological Survey to jointly carry out a transboundary hydrogeological study of the Potsdam sandstone aquifer. The Potsdam sandstone aquifer consists of a lower unit of arkose and conglomerate and an upper unit of well-cemented quartz arenite. The thickness of the regional aquifer ranges from nil at the base of Adirondacks to more than 500 m near the St. Lawrence River. Glacial till, littoral sand and gravel, and marine silt and clay discontinuously overlie the aquifer. The aquifer's water budget is characterized by low rates of surface runoff and high rates of infiltration and sub-surface runoff. Major recharge areas are present at higher altitudes near and to the south of the border. Strong downward hydraulic gradients in these areas result in cascading water and water-level depths of more than 30 m in deep wells. Bedding in the Potsdam sandstone is gently dipping with fractures along sub-horizontal bedding planes forming major flow conduits. Bedrock folds and faults, mainly developed by east-west compression during the Appalachian orogenies, locally complicates aquifer geometry and groundwater flow. Hydraulic tests (pump, slug, flowmeter and straddle packer) indicate similar horizontal transmissivities in the lower and upper aquifer units. However, differences in lithology and structure of the aquifer units impose some apparent differences in hydraulic properties and groundwater flow patterns. In the lower unit, regional flow appears to be sustained by a limited number of laterally extensive bedding-plane fractures. During aquifer tests, significant drawdown was observed in observation wells at distances of more than a kilometer from pumped wells, whereas nearby nested piezometers screened in different bedding planes showed markedly less drawdown. Groundwater users that exploit the same permeable fracture zones are thus highly interdependent and vulnerable to their respective pumping rates. On the other hand, the more densely fractured upper unit apparently has more dispersed groundwater flow. Numerical modeling of the regional groundwater flow substantiates these differences. In order to match measured hydraulic heads, the calibrated vertical anisotropy of the lower unit was in average 100 times higher than that of the upper unit. Simulated capture areas of production wells display elongated forms commonly crossing the Quebec-New York border. Simulated scenarios are the first step towards the joint management of the groundwater resources.
DE: 1828 Groundwater hydraulics
DE: 1847 Modeling
DE: 1859 Rocks: physical properties
DE: 1865 Soils (0486)
DE: 1876 Water budgets
SC: Hydrology [H]
MN: Fall Meeting 2005