Buried Valleys Aquifer System

Aquifer System

Version Metadata
1924051c-d22a-48d5-b763-cc66dc5d271b
Project
Buried Valleys - Blanket aquifers

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Buried Valleys Aquifer System unit description

Update:2014-03-24
Buried valleys occur across Canada and may be incised into either bedrock of overlying surficial sediment and infilled by a broad range of sediment facies (e.g. Russell et al. 2004). Across the Canadian Prairies over 20 000 km of buried valleys have been identified (Russell et al., 2013) mostly incised into Cretaceous shales (Cummings et al., 2012). Buried valleys within the surficial succession, also known as inter till aquifers, are commonly recognized but rarely mapped. Three different styles of buried valleys have been identified (e.g. Pugin et al., 2014) and attributed to erosion and infill by fluvial, glaciofluvial and glacial processes in the preglacial and glacial period (Cummings et al., 2012; Atkinson et al., 2013; Pugin et al., 2014). Alpha valleys are regional bedrock valleys inferred to be preglacial. Beta valleys are deeper incised parts within alpha valleys that may subtend from unconformities within the till succession. Gamma valleys are inferred to be the youngest, the narrowest and to be incised into either bedrock or surfical sediment, and may subtend from unconformities within the surficial sediment. The thickness of the surficial sediment filling and burying buried valleys is up to 350 m (e.g. Cummings et al., 2012). Buried-valleys fills are comprised of sand, gravel, mud and diamicton (till). Numerous valleys contain permeable sand and (or) gravel at depth, and shallower stratigraphy is commonly mud-rich diamicton (till). The resulting heterogeneity may compartmentalize the aquifers and create localized flow systems (e.g. Shafer and Pusc, 1992). The hydraulic characteristics of buried valleys are variable and it is necessary to carefully assess the geological setting of individual buried valleys. The till-dominated sediment that covers the Prairies is a primary control on the hydrogeological characteristics of buried-valley aquifers. It limits recharge to these aquifers. In areas where several tens of metres of till overlie buried valleys, hydraulic head responses to precipitations tend to be muted or absent, and recovery of head following intense pumping can take years (e.g. Maathuis and van der Kamp, 2003; Van der kamp and Maathuis, 2002). Some buried valleys may operate as regional groundwater drains, with modern rivers commonly functioning as discharge zones. A number of buried valleys have been the focus of study, notably the Estevan in Southern Saskatchewan (Maathuis and van der Kamp, 2003), Spiritwood in Southern Manitoba (Pugin et al., 2014), and valleys in the Cold Lake area of Alberta (Atkinson et al., 2013). The Spiritwood Aquifer system in particular demonstrates this heterogeneity in valley erosion and fills with several generations of valleys of different dimensions and orientations (Pugin et al., 2014). Many of the intermediate depth valleys form inter-till aquifers and provide possible hydraulic connections to deeper buried valleys. The hydraulic boundaries of buried valleys are variable and it is necessary to carefully assess the geological and hydrogeological setting of individual buried valley segments. The resulting heterogeneity may compartmentalize the aquifers and create localized flow systems (e.g. Shafer and Pusc, 1992).
Physiography
Hydrogeological regionWestern Canada Sedimentary Basin
Hydrogeological context
ReliefThe terrain is undulating and elevations vary from 500 to 1000 m. Lowest elevations are located near the river, where the terrain is gullied and characterized by significant slopes. The highest terrain is found at the west boundary of the area, representing the Rocky Mountains. Relief across the Spiritwood study area is approximately 30 metres. In the broader region, however, relief can be up to 300 m between Turtle Mountain forming the top of the watershed, and along the Pembina and Souris River Valleys that are incised about 40-75 m into the till plain. The till plain lies between Turtle Mountain and the river valleys and slopes gently to the northeast with limited local relief and includes areas with numerous prairie potholes with permanent and discontinuous water coverage.
Area109095.00 km2
Lithology
DescriptionThe buried valleys are referring to valleys that are incised into bedrock and buried by till. The buried-valleys are filled with sand, gravel, mud and diamicton (till). Numerous valleys contain permeable sand and (or) gravel bodies along their bases, and their upper portions are commonly filled with mud-rich diamicton (till). The diamicton-dominated sediment package forms a regional drape over bedrock. The latter mainly consists of poorly consolidated, carbonate-poor Cretaceous shale. Cretaceous sandstone forms bedrock locally and Paleozoic carbonate rock forms the bedrock substrate along the northeastern feather edge of the West Canadian Sedimentary Basin. The Spiritwood valley extends southward from the Brandon, Manitoba area, through Cartwright, Manitoba, into and across North Dakota, approximately 500 km in length (e.g. Cummings et al., 2012) . The Spiritwood buried valley consists of a series of nested and stacked valleys eroded in both bedrock and overlying sediment (Pugin et al., 2014). The main (alpha) valley is eroded into the shale bedrock and is typically 10 km wide and 60-70 m deep in Canada (Oldenborger et al., 2010). Two deeper (100 m), narrower (1-2 km) valleys are eroded within the broader alpha valley. The beta valleys are infilled with sand and gravel and muddy diamicton (Crow et al., 2012). Based on seismic data, the alpha valley fill has a complex geometry of multiple fill and erosional cycles with sediment hosted valleys subtending from erosional surfaces that may extend to bedrock (Pugin et al., 2014). Gamma valleys both crosscut and lie within the broader alpha valley. They are generally narrow, steep sided and have variable fill. Diamicton (till) is the dominant surficial unit (Elson, 1960).
Source
Aquifer
AquifersList of aquifers - Sedimentary aquifers of buried valleys - Spiritwood alpha valleys, beta valleys and gamma valleys

Unit properties

Surficial aquifer media
Typical value:porous
Description Sand, gravel, mud, and diamicton (till) are common valley fill components. Borehole data suggests a predominantly diamicton fill (Crow et al. 2012), however airborne geophysical data coupled with seismic reflection profiles suggest a more complex fill with greater textural variability (Pugin et al., 2014; Oldenborger (2010). Aquifer units are inferred to occur at a variety of depths in a variety of stratigraphic positions within the Spiritwood study area. (Pugin et al., 2013).
Source Architecture of buried valleys in glaciated Canadian Prairie regions based on high resolution geophysical data
Methode Aquifers units defined by drilling, seismic reflection, airborne aeromagnetism surveys, ground-based resisitvity, and downhole geophysics
Confinement
Typical value:confined - semi confined
Description Aquifers are confined by variable diamicton (till) units that are up to 80 m thick. Low conductivity signal in the AEM may correspond to more permeable areas and highlights spatial variability in the aquitard character. Gamma channels may provide hydraulic connections to inter-till and buried valley aquifers.
Source Downhole geophysical data from boreholes along the Spiritwood buried valley aquifer near Cartwright, Killarney, and southeast of Brandon, Manitoba
Methode AEM
Surficial sediment thickness
42.92 m Range: [0 to 128.28] m
Description These values can come from subtracting the bedrock elevation from the surface DEM which should be the same for all models.
Source Geological, hydrogeological, geophysical, and geochemistry data from a cored borehole in the Spiritwood buried valley, southwest Manitoba
Methode Typical value is the mean.
Hydrogeological unit thickness
13.03 m Range: [0 to 61.55] m
Description Hydrogeological unit thicknesses and aquifer volumes are based on geological model surfaces rather than borehole logs. Modelled geologic contact surfaces are interpolated and extrapolated based on AEM data, seismic profiles and borehole log contacts. Some over-estimation of sediment thickness compared to raw borehole log data may result, particularly for the buried valley aquifer for which there are few boreholes that penetrate it.
Methode mean used for typical value
Well depth
34.83 m Range: [3.048 to 136.25] m
Methode Data from wells database. Typical value expressed as a mean.
Groundwater depth
9.76 m Range: [0 to 54.12] m
Methode From well database or by extracting from calculations in GIS. Typical value expressed as a mean.
Surficial unit hydraulic conductivity
Description Mud rich diamicton unweathered: 1E-11 to 1E-9 m/s Mud rich diamicton weathered: 1E-9 to 1E-7 m/s Intertill sand and gravel: 1E-4 to 1E-3 m/s
Bedrock hydraulic conductivity
Range: [0 to 0] m/s
Description Only regional data available. Spiritwood is inferred to be underlain by fractured shales of the Odanah Member of the Pierre Shale. The Odanah Member consists mainly of amorphous silica with a fairly low content of clay minerals. The permeability of the intergranular medium is likely very low. Fracturing in the shales appears to be irregular and unpredictable. Groundwater flow in the Odanah shale is mostly along fractures, joints and bedding plane openings. Yields from wells are typically less than 0.5 L/s but yields in excess of 1 L/s are not uncommon and yields as high as 10 L/s are reported.
Source Groundwater in Manitoba: hydrogeology, quality concerns, management
Methode Litterature review - to be completed
Regional precipitation
383.3 mm/y Range: [322.6 to 446.1] mm/y
Methode Precipitation data are from Environment Canada. The value represents the average of the climate normals (1981-2010) measured on the stations distributed in or near the hydrogeological unit. The stations were selected so the average precipitation is as representative as possible of the whole hydrogeological unit.
Regional evapotranspiration
23.6 mm/y Range: [19.6 to 27.5] mm/y
Methode Evapotranspiration data are from Environment Canada. The value represents the average of the climate normals (1981-2010) measured on the stations distributed in or near the hydrogeological unit. The stations were selected so the average precipitation is as representative as possible of the whole hydrogeological unit.
Regional recharge
Range: [ to 2] mm/y
Description The thick till cover and fill of the Spiritwood Buried Valley in Canada limits recharge to deep groundwater flow paths which likely averages less than 2 mm/yr regionally. Much of the flow to buried valley aquifers may occur through vertical hydraulic connections provided by inter-till aquifers.
Source The Unusual and Large Drawdown Response of Buried‐Valley Aquifers to Pumping
Regional discharge
Description The deep Spiritwood buried (beta) valley drains to the northwest and northeast where the buried valley intersects modern incised valleys. A baseflow survey during extended drought conditions confirmed perennial flow in these areas.
Source Buried-valley aquifers in the Canadian Prairies: geology, hydrogeology, and origin
Hydrogeological unit yield
Description There is currently little data on yield for the Spiritwood Aquifer in Canada. One municipal well has a capacity of approximately 60 L/s (800 IGPM). Yields from Towner County in North Dakota along the Canada US border are reported to be as high as 63-95 L/s (1000-1500 USGPM (Randich and Kuzniar, 1984.). Although buried valley aquifer yields may be high due to permeable sediment, limited groundwater replenishment may severely limit sustainable yields (e.g. van der Kamp and Maathuis, 2006).
Source Groundwater in Manitoba: hydrogeology, quality concerns, management
Groundwater usage
Typical value:agricultural - domestic - industrial
Description In Manitoba, groundwater from the Spiritwood Buried Valley Aquifer is primarily exploited for municipal use, communal loading stations (primarily agricultural use) and private (mostly farm) wells. Large scale central pivot irrigation is not used as it is in southern areas of North Dakota.
Source Buried-valley aquifers in the Canadian Prairies: geology, hydrogeology, and origin