K.U. Weyer and James C. Ellis
Proceedings, IAH/CGS International Symposium on Regional Groundwater Flow: Theory, Applications and Future Development
Xi'an, China, June 22-23, 2013

© 2013, WDA Consultants Inc.


Introduction

A number of practical considerations have put the presumed existence of long range groundwater flow into the centre of interest in the area of the Northern Great Plains in Canada, such as CO₂ sequestration in Alberta and Saskatchewan as well as mining of the Athabasca oil sands and subsurface waste disposal (Swan Hills) in Alberta. Thus, in this area, regional groundwater flow has moved from the realm of academic studies to become an important component of environmental concerns by industry, governments and the public.


Figure 1: Long range regional groundwater flow systems [1] and [2] in the prairie provinces (Alberta, Saskatchewan and Manitoba) and US states (Montana, North and South Dakota) proposed by Bachu [1999], Anfortet al. [2001], and Downey et al. [1987]).

One such long range flow system has been postulated by Downey et al. [1987] with recharge into deep aquifer systems in the Beartooth Mountains, Absaroka Range, and the Big Horn Mountains, located off Yellowstone National Park. They are of alpine character exceeding 3000 m in elevation. Associated discharge areas were presumed to be in South Dakota, North Dakota, Manitoba and Saskatchewan. The assumed flow system [1] of about 1100 km length is part of Downey at al.’s [1987] postulate.

Long range system [2] is about 1600 km long [Bachu, 1999, Anfort et al., 2001] and recharges at the outcrop of the aquifer system in the Big Snowy Anticlinorium and Big Horn Mountains in Montana (Figure 1), and discharges about 1600 km further north into the Peace River. Based on thermodynamical principles and head data, Weyer [2012] showed this construct to be physically untenable and contrary to head data provided by Bachu et al. [1993].

The methods applied in the investigations of these systems related to chemistry and basic groundwater dynamics. This paper examines the validity of groundwater dynamic assumptions used. The outdated concept applied for recharge and discharge of deep aquifer systems as shown in Figure 2A. Recharge of the aquifer system is assumed to occur only at the mountainous outcrop area while discharge only occurs in the ‘downstream’ outcrop area of the very same aquifer system. The overlying ‘impermeable’ aquitard prevents communication between the aquifer system and the overlying groundwater body and the groundwater table. For about 50 years, the concept has been replaced by Freeze and Witherspoon [1967], which recognized aquitards (and caprocks) as an integral part of groundwater flow systems (Figure 2B).


Figure 2: Comparison of outdated [Figure 2A; Hubbert, 1953] and modern [Figure 2B; Freeze and Witherspoon, 1967] concepts with respect to the role of aquitards in regional groundwater flow.

The outdated concept of Figure 2A leads to long range groundwater flow systems between the two outcrop areas of the aquifer system. This is the only ‘hydraulic’ reason why the two long range groundwater flow systems ([1] and [2]) have been postulated by their supporters. In applying this outdated concept to CO2 sequestration and the mining of the Athabasca oil sands, erroneous operational recommendations were provided to industry, governments, and the public which will need to be revisited [Weyer, 2012; 2013].

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