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TitleNumerical simulation of groundwater flow in the Chateauguay River Aquifers
AuthorLavigne, M -A; Nastev, M; Lefebvre, R
SourceCanadian Water Resources Journal vol. 35, no. 4, 2010 p. 469-486,
Alt SeriesEarth Sciences Sector, Contribution Series 20100008
Mediapaper; on-line; digital
File formatpdf
NTS31B/16; 31G/01; 31H/04; 31H/05
AreaChateauguay River; New York State; Canada; United States
Lat/Long WENS-74.5000 -73.5000 45.5000 44.7500
Subjectshydrogeology; aquifers; groundwater; groundwater resources; groundwater surveys; groundwater regimes; groundwater flow; groundwater discharge; discharge rates; hydraulic analyses; hydraulic conductivity; Chateauguay River
Illustrationslocation maps; block diagrams; tables; histograms; plots
ProgramQuantitative risk assessment, Public Safety Geoscience
AbstractThe Chateauguay River watershed extends over northeastern New York State (USA) and southwestern Quebec (Canada). Fractured sedimentary rocks of the St. Lawrence Platform host the regional aquifers. Quaternary sediments of variable thickness of up to 45 m overlie the bedrock. The geometric mean hydraulic conductivity of the bedrock aquifers obtained from 548 field measurements is 5.1 × 10-5 m/s with a standard deviation of 0.7 of the logarithms. The modelled area extends from the foothills of the Adirondacks to the St. Lawrence River and covers 2,850 km2. The numerical groundwater flow model was developed using the finite element simulator FEFLOW. The model has 13 layers with layer thicknesses ranging from 5 m for the top layer to 75 m for the bottom layer. The average thickness of the numerical model is 655 m, for a total volume of 1,868 km3. The St. Lawrence River is considered as a specified head boundary; the base and other lateral limits are considered as noflow boundaries, whereas a head and conductivity-dependent boundary is specified along major streams and wetlands. Spatial recharge rate is applied as a specified flux across the top of the model and was fixed during calibration to reduce model uncertainty. Groundwater withdrawal of 34 Mm3/yr is assigned using sinks for major wells and as a uniform negative flux across the top of the model to account for domestic and other diffuse uses. Calibration was carried out against 153 hydraulic head measurements, with horizontal hydraulic conductivity and vertical anisotropy used as calibration parameters. The regional groundwater flow amounts to 268 Mm3/yr: 12.7% is withdrawn for domestic purposes; aquifer contribution to streams and wetlands is 176 Mm3/yr, and 55 Mm3/yr is discharged to the St. Lawrence River. Groundwater flow appears to be controlled by the sub-horizontal bedding planes contributing to relatively high vertical anisotropy.