Abstracts

This paper outlines the District’s plan for transition to increased reliance on groundwater,
including the implementation of microbiological manganese removal, additional source development,
and water treatment requirements in the context of the recently released Drinking
Water Treatment Objectives for Groundwater Supplies in B.C. The deep basalt aquifer will also
be discussed in the context of basalt hydrogeology fundamentals, as it is a little known but
regionally extensive aquifer system that is not heavily developed in Interior of B.C.
245 - Regional groundwater flow in the inter-till and buried-valley
aquifers, southwestern Manitoba
Hinton, M.J., Logan, C.E., Oldenborger, G.A. & Pugin, A.J.-M.
Geological Survey of Canada, Natural Resources Canada, Ottawa, Ontario, Canada
Inter-till and buried-valley aquifers are among the main sources of groundwater in the
Prairies. The Spiritwood buried-valley aquifer system extends from Manitoba and across
North Dakota where it has been a significant source for groundwater supply for decades
yet its resource potential in Manitoba has not been evaluated. The Geological Survey of
Canada (GSC) has been studying the regional geology and hydrogeology of the Spiritwood
buried-valley aquifer in southwestern Manitoba. Helicopter time domain electromagnetic
(HTEM) and high resolution seismic reflection (HRSR) surveys permitted
detailed mapping of inter-till and buried-valley aquifers within the study area. The main
buried valley is a broad 10-15 km wide and 60-70 m deep valley cut into Cretaceous Pierre
shale. A series of nested channels of different age, origin, dimensions and orientations
are cut into bedrock and within the sand/silt till. Where these channels are filled with
coarse sediment, they form aquifers: deep buried-valley aquifers (60-100 mbgs) incised
into shale below the base of the broad buried valley, and inter-till aquifers within the till.
A 3D numerical geological model of the regional bedrock surface and sediments was developed,
using Leapfrog Hydro geological modelling software. A significant feature of
the geological model is that the nested channels and fans that form inter-till aquifers together
with the fractured bedrock surface may provide more permeable pathways to deep
buried-valley aquifers. Another significant finding is the discovery that the buried-valley
aquifer outcrops in incised surface valleys where sustained baseflow was measured during
a period of extended drought.
Regional groundwater flow generally follows topography but is perpendicular to the orientation
of the main buried valley. However, flow also occurs along the deep buried valley
which acts as a regional drain towards the incised surface valleys. Both hydraulic and
HTEM results suggest that there are no transverse hydraulic boundaries within the deep
buried-valley aquifer. A steady state finite element numerical groundwater model has been
developed from the geological model to: i) assess the different flow pathways within the
inter-till and deep buried-valley aquifers, and ii) constrain the estimates of groundwater
flow. The numerical flow model replicates the regional flow patterns, discharge zones and
the groundwater divide in the deep buried-valley aquifer. Results to date suggest that,
despite the presence of preferred hydraulic pathways, natural replenishment of the deep
buried-valley aquifer is small. © Her Majesty the Queen in right of Canada 2015.
74 IAH-CNC 2015 WATERLOO CONFERENCE