Numerical Modelling in Support of Provincial Groundwater Inventory Program
Authors: Amandeep Singh, Joseph Riddell, G.F. Huff, Dan Palombi
The Alberta Geological Survey (AGS) and Environment and Sustainable Resource Development (ESRD) are working together on the Provincial Groundwater Inventory Program (PGIP) to develop adaptable and science-based decision making tools supporting policy development and regulation to manage groundwater resources. The first phase of PGIP is focused on developing a static geological model that integrates multiple sources of data and analysis into a single framework that will be used for the subsequent phases (i.e. building groundwater models and integrating them in a decision support system). To support the modelling phase of PGIP, a regional-scale study of groundwater flow is being undertaken in the Western Canada Sedimentary Basin, comprising parts of Alberta, Saskatchewan and British Columbia. The objective of the study is to develop a regional scale numerical model of basin-scale hydrogeology which will subsequently provide boundary conditions for local-scale groundwater management models.
The regional scale model under development includes post-Colorado group aquifers, composed of late Cretaceous to Recent sediments, attaining maximum thicknesses of >2600 m. The study area is bound to the west by the Brazeau-Waptiti thrust (deformation) belt and to the south by the Canada-USA international border. The Belly River group zero edge along with Pierre Shale Group (Saskatchewan) forms lateral boundaries in the north and east, whereas top of Colorado group (Lea Park formation) forms the basal boundary of our model. Major surface water bodies and their larger tributaries within the modelled area are the Peace, Athabasca, North and South Saskatchewan rivers and mountain streams. Aquifer units identified for the study include the major litho-stratigraphic units and their equivalents from land surface to the top of the Lea Park Formation consisting of the Quaternary sediments, and the Paskapoo, Scollard, Horseshoe Canyon formations and the Belly River Group. The regional aquitards in the study area have been delineated as the Battle and Bear Paw formations. Previous work in the Alberta Basin has demonstrated that, in addition to topography controlled flow regimes, a substantial part of the basin contains sub-hydrostatic flow regimes. The flow model attempts to honor the effects of sub-hydrostatic conditions to reflect its influence on regional water balance and flow directions. The block-centric, finite difference groundwater code MODFLOW is being used to construct the basin-scale model.
Preliminary results from the groundwater flow modelling indicate predominance of topography-driven, local- to intermediate-scale flow systems in the upper hydrostratigraphic units (Quaternary, Paskapoo, Scollard) with recharge of these units occurring in the foothills of the
Rocky Mountains. The Battle aquitard, where present, acts as a regional flow barrier in the model. Flow paths in the Horseshoe Canyon Formation and Belly River Group hydrostratigraphic units are controlled by regional scale topography-driven flow systems and sub-hydrostatic pressure regimes. The upper units (i.e. the Paskapoo and the Scollard units) are influenced by the presence of sub-hydrostatic conditions in deeper units but in general the affected zone is beyond typical groundwater water source wells.
The Alberta Geological Survey (AGS) and Environment and Sustainable Resource Development (ESRD) are working together on the Provincial Groundwater Inventory Program (PGIP) to develop adaptable and science-based decision making tools supporting policy development and regulation to manage groundwater resources. The first phase of PGIP is focused on developing a static geological model that integrates multiple sources of data and analysis into a single framework that will be used for the subsequent phases (i.e. building groundwater models and integrating them in a decision support system). To support the modelling phase of PGIP, a regional-scale study of groundwater flow is being undertaken in the Western Canada Sedimentary Basin, comprising parts of Alberta, Saskatchewan and British Columbia. The objective of the study is to develop a regional scale numerical model of basin-scale hydrogeology which will subsequently provide boundary conditions for local-scale groundwater management models.
The regional scale model under development includes post-Colorado group aquifers, composed of late Cretaceous to Recent sediments, attaining maximum thicknesses of >2600 m. The study area is bound to the west by the Brazeau-Waptiti thrust (deformation) belt and to the south by the Canada-USA international border. The Belly River group zero edge along with Pierre Shale Group (Saskatchewan) forms lateral boundaries in the north and east, whereas top of Colorado group (Lea Park formation) forms the basal boundary of our model. Major surface water bodies and their larger tributaries within the modelled area are the Peace, Athabasca, North and South Saskatchewan rivers and mountain streams. Aquifer units identified for the study include the major litho-stratigraphic units and their equivalents from land surface to the top of the Lea Park Formation consisting of the Quaternary sediments, and the Paskapoo, Scollard, Horseshoe Canyon formations and the Belly River Group. The regional aquitards in the study area have been delineated as the Battle and Bear Paw formations. Previous work in the Alberta Basin has demonstrated that, in addition to topography controlled flow regimes, a substantial part of the basin contains sub-hydrostatic flow regimes. The flow model attempts to honor the effects of sub-hydrostatic conditions to reflect its influence on regional water balance and flow directions. The block-centric, finite difference groundwater code MODFLOW is being used to construct the basin-scale model.
Preliminary results from the groundwater flow modelling indicate predominance of topography-driven, local- to intermediate-scale flow systems in the upper hydrostratigraphic units (Quaternary, Paskapoo, Scollard) with recharge of these units occurring in the foothills of the
Rocky Mountains. The Battle aquitard, where present, acts as a regional flow barrier in the model. Flow paths in the Horseshoe Canyon Formation and Belly River Group hydrostratigraphic units are controlled by regional scale topography-driven flow systems and sub-hydrostatic pressure regimes. The upper units (i.e. the Paskapoo and the Scollard units) are influenced by the presence of sub-hydrostatic conditions in deeper units but in general the affected zone is beyond typical groundwater water source wells.
