| Title | A unified hydrogeological conceptual model of the Milk River transboundary aquifer, traversing Alberta (Canada) and Montana (USA) |
| Author | Pétré, M A; Rivera, A; Lefebvre, R; Goblet, P |
| Source | Hydrogeology Journal vol. 24, issue 7, 2016 p. 1847-1871, https://doi.org/10.1007/s10040-016-1433-8 |
| Year | 2016 |
| Alt Series | Earth Sciences Sector, Contribution Series 20150304 |
| Publisher | Springer |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Alberta |
| NTS | 72E |
| Area | Montana; United States |
| Lat/Long WENS | -113.0000 -109.0000 50.0000 48.5000 |
| Subjects | groundwater; groundwater resources; formation waters, commodity; hydraulic gradients; hydraulics; conceptual model; grounwater exploitation |
| Illustrations | location maps; graphs; histograms; schematic diagrams |
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| Program | Aquifer Assessment & support to mapping, Groundwater Geoscience |
| Abstract | A conceptual model of the transboundary Canada-USA Milk River Aquifer (MRA) was developed based on literature, focused field work and a 3D geological model. The MRA corresponds to the Virgelle Member of
the Milk River Formation (called Eagle Formation in Montana). The MRA is confined by aquitards of the Pakowki/Claggett Formation, and overlays Colorado Group aquitard. Confinement varies with changes in surface topography, but especially due to
buried valleys eroding part of the top aquitard. The up-gradient MRA limit is the Virgelle outcrop near the international border and along the Sweetgrass Arch in Montana. The down-gradient limit is the unconformity separating the Virgelle Member from
the gas-bearing sandy shale Alderson Member. The MRA shows larger transmissivity areas leading to preferential flowpaths confirmed by natural geochemical tracers. Tritium and 14C delineate restricted recharge areas along the MRA outcrops on both
sides of the international border. Drastic changes in hydraulic gradient indicate that the Milk River intercepts an important proportion of the groundwater flowing through the MRA. Beyond the Milk River, groundwater flows quite slowly, as shown by
36Cl residence times exceeding a million year. There is no other direct discharge zone, but vertical leakage occurs through the underlying Colorado Aquitard and upward along buried valleys, which seem to act as drains and correspond to artesian
areas. The MRA contains a mostly fossil groundwater resource not significantly renewed. Groundwater exploitation thus far exceeds renewal, a situation requiring properly managed MRA groundwater depletion. |
| Summary | (Plain Language Summary, not published)
A conceptual model of the Milk River transboundary Aquifer (Canada-USA) is proposed. It was developed based on literature, focused field work and a 3D
geological model. This model aims to link hydrogeology and geochemical evidences on both sides of the international border. This model allows a better understanding of the functioning of the aquifer and the processes that might occur. Preferential
flow path have been highlighted from hydrogeological parameters and have been confirmed by geochemical data. The Milk River intercepts a large part of the groundwater flux, which in turn leads to a small and low-velocity residual flux, as indicated
by residence time (obtained from isotopic analysis) over a million year. The aquifer contains mostly fossil water and is not significantly renewed. this situation requires a proper managed groundwater depletion of the aquifer. |
| GEOSCAN ID | 297323 |
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