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TitleGeostatistical mapping of leakance in a regional aquitard, Oak Ridges Moraine area, Ontario, Canada
AuthorDesbarats, A JORCID logo; Hinton, M JORCID logo; Logan, C EORCID logo; Sharpe, D R
SourceHydrogeology Journal vol. 9, no. 1, 2001 p. 79-96,
LinksOak Ridges Moraine web site
LinksMoraine d'Oak Ridges, site web
Alt SeriesGeological Survey of Canada, Contribution Series 2000183
PublisherSpringer Nature
Mediapaper; on-line; digital
RelatedThis publication is related to Geostatistical mapping of leakance in a regional aquitard, Oak Ridges Moraine area, Ontario
File formatpdf
NTS30M/13; 30M/14; 30M/15; 30M/16NE; 30M/16NW; 31C/04SW; 31C/04NW; 31D/01; 31D/02; 31D/03; 31D/04
AreaToronto; Newmarket; Aurora; Trenton; Port Hope; Whitby
Lat/Long WENS -80.0000 -77.7500 44.2500 43.7500
Subjectsmathematical and computational geology; hydrogeology; geostatistics; statistical analysis; statistical methods; statistics; hydraulic analyses; groundwater flow; aquifers; glacial deposits; tills; modelling; Oak Ridges Moraine; Newmarket Till; aquitards; leakance; Cenozoic; Quaternary
Illustrationssketch maps; graphs; plots; histograms; block diagrams
ProgramOak Ridges Moraine NATMAP Project
AbstractThe Newmarket Till forms a regionally extensive aquitard separating two major aquifer systems in the Greater Toronto area, Canada. The till is incised, and sometimes eroded entirely, by a network of sand- and gravel-filled channels forming productive aquifers and, locally, high-conductivity windows between aquifer systems. Leakage through the till may also be substantial in places. This study investigates the spatial variability of aquitard leakance in order to assess the relative importance of recharge processes to the lower aquifers. With a large database derived from water-well records and containing both hard and soft information, the Sequential Indicator Simulation method is used to generate maps of aquitard thickness and window probability. These can be used for targeting channel aquifers and for identifying potential areas of recharge to the lower aquifers. Conductivities are modeled from sparse data assuming that their correlation range is much smaller than the grid spacing. Block-scale leakances are obtained by upscaling nodal values based on simulated conductivity and thickness fields. Under the "aquifer-flow'' assumption, upscaling is performed by arithmetic spatial averaging. Histograms and maps of upscaled leakances show that heterogeneities associated with aquitard windows have the largest effect on regional groundwater flow patterns.

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