ArticlePDF Available

GROUNDWATER MODELLING: FROM GEOLOGY TO HYDROGEOLOGY

Authors:

Abstract and Figures

1. ABSTRACT Three-dimensional mapping has extensively developed in the last decade; geological mapping being the area where these developments are more striking. 3D geological mapping has a myriad of applications in the domains of basin analysis, geophysics, geostatistics, geothermal and energy resources, etc. A parallel domain of development has been three-dimensional groundwater modelling: regional groundwater systems, surface water-groundwater interactions, radioactive waste disposal, etc. Whilst these developments have substantially advanced both domains, we see that we are still lagging behind having a clear interface between geological mappers and groundwater modelers. Unfortunately, geologists and hydrogeologists are still working on their own fields more or less separately, and their communication is still poor. Science and technology and available tools abound, but both groups still do not take full advantage to benefit each other. This short essay is a recap, a synthesis of what we see today in the domains of 3D geological mapping and 3D groundwater modelling. 2. MODELLING Modelling is a very wide term as used and applied in earth sciences. We have geological models, conceptual models, hydrogeological models, mathematical models, analytical models, numerical models, stochastic models, deterministic models. There are marked differences amongst these models, but also many similarities depending on their use and domains of applications. The clear link between geological mapping and modelling, and groundwater modelling, is the building of a conceptual model. A conceptual model in hydrogeology is the pictorial representation of the groundwater flow system, frequently in the form of a block diagram. Simplifying assumptions and qualitative interpretation of data and information of a site are included in the conceptual model; its development is actually synonymous with site characterization. It is there where geologists and hydrogeologists should converge and add value to the groundwater model by bringing their respective knowledge to the table. In building a conceptual groundwater flow model, for instance, there is strong emphasis on rocks (stratigraphy) and geological processes from 3D geological mappers; whereas groundwater modelers put their emphasis in groundwater flow mechanisms and aquifer parameters; that is a thin layer between geologists and hydrogeologists which must be further expanded.
Content may be subject to copyright.
GROUNDWATER MODELLING: FROM GEOLOGY TO
HYDROGEOLOGY
Alfonso Rivera
Geologic Survey of Canada, 490 rue de la Couronne, QC, Quebec G1K 9A9, Canada, arivera@nrcan.gc.ca
1. ABSTRACT
Three-dimensional mapping has extensively developed in the last decade; geological mapping being the
area where these developments are more striking. 3D geological mapping has a myriad of applications in
the domains of basin analysis, geophysics, geostatistics, geothermal and energy resources, etc. A parallel
domain of development has been three-dimensional groundwater modelling: regional groundwater systems,
surface water-groundwater interactions, radioactive waste disposal, etc. Whilst these developments have
substantially advanced both domains, we see that we are still lagging behind having a clear interface
between geological mappers and groundwater modelers. Unfortunately, geologists and hydrogeologists are
still working on their own fields more or less separately, and their communication is still poor. Science and
technology and available tools abound, but both groups still do not take full advantage to benefit each other.
This short essay is a recap, a synthesis of what we see today in the domains of 3D geological mapping and
3D groundwater modelling.
2. MODELLING
Modelling is a very wide term as used and applied in earth sciences. We have geological models,
conceptual models, hydrogeological models, mathematical models, analytical models, numerical models,
stochastic models, deterministic models. There are marked differences amongst these models, but also
many similarities depending on their use and domains of applications. The clear link between geological
mapping and modelling, and groundwater modelling, is the building of a conceptual model. A conceptual
model in hydrogeology is the pictorial representation of the groundwater flow system, frequently in the form
of a block diagram. Simplifying assumptions and qualitative interpretation of data and information of a site
are included in the conceptual model; its development is actually synonymous with site characterization. It is
there where geologists and hydrogeologists should converge and add value to the groundwater model by
bringing their respective knowledge to the table. In building a conceptual groundwater flow model, for
instance, there is strong emphasis on rocks (stratigraphy) and geological processes from 3D geological
mappers; whereas groundwater modelers put their emphasis in groundwater flow mechanisms and aquifer
parameters; that is a thin layer between geologists and hydrogeologists which must be further expanded.
2.1 Geology mapping-Groundwater modelling links
To conceive and build a groundwater model (e.g., for water resources), one must go through a geological
model; both models are complex in nature and require experts in each domain with very specific knowledge.
In general, the hydrogeologist begins building of the groundwater model from a rough idea of groundwater
flows, backwards into describing the “reservoir”; the geologist, on the other hand, begins building of the
geological model from the knowledge of the geology of the region under study, forwards into proposing a
“reservoir”. The hydrogeologist would tend to simplify the geology in an attempt to explain groundwater
fluxes. His numerical grid would be built to accommodate traits of groundwater flow systems into “aquifers”
defined by hydrostratigraphy; he would be interested in water pressures, flows and the physical and
chemical parameters describing these. The geologist would tend to amplify the geological processes in an
attempt to explain reservoir systems. His map and associated 3D model would be built to accommodate a
detailed succession of layers, the history of rocks and an extensive explanation of the geological processes
that have shaped the rocks with time (tectonics, magnetism, Quaternary stratigraphy). Both approaches are
very rich and should complement; that is however not always the case.
The current emphasis in both domains is on how well one can generate model grids. We have seen an
explosion of grid generators in the last 10 years; petroleum engineering and radioactive waste disposal
being the most advanced ones. There are different motivations and interests in each of these domains.
Given the environmental and social issues linked to the radioactive waste, the impetus and motivations of
this industry, for instance, has been visualization. In this case, grid generators are designed to show long-
term processes and to virtually show the public how radioactivity from the wastes is contained in deep
underground repositories. They need “to convince” the public and sponsors of the safety of underground
structures. Given the very important investments in the oil industry, petroleum engineering has developed a
very extensive set of numerical tools to build reservoir models used in their surveys. Groundwater modelers
have taken advantage of some of these developments from both industries.
In addition to building model grids and a conceptual model (the geological modeling process), groundwater
modelers also need numerical hydrodynamic models to solve for the physical-chemical processes of
groundwater. Hydrogeologists have also learnt extensively from developments of both the radwaste and oil
industries.
2.2 Developing models
In summary, when we model, we should distinguish between a geological model (GM) a conceptual model
(CM) and a hydrogeological model (HM). To build a hydrogeological model one needs:
Discretisation of space (Finite Differences Method; Finite Element Method) and time;
A numerical code to solve for a set of equations;
Boundary conditions;
Initial conditions;
Set of model parameters, (permeability, storativity, dispersivity) per node, per element or per
layer;
Set of data of the stresses in the system (pumping); and
Set of data for calibration (heads, concentration, compaction).
The assemblage of these attributes constitutes the hydrogeological (or groundwater) model. These
attributes however, depend on the geological model; if the GM is wrong, the conceptual model could be
wrong and the HM model will not be successful in simulating the groundwater processes. Thus, it is very
important that experts in geological modelling and in groundwater modelling communicate and share their
respective knowledge and expertises (figure 1).
Figure 1 Geological survey (left) into a CM (middle) as basis for building a HM; the later
contains both the “reservoir” and the hydrodynamics of groundwater.
We see clear links between geological mapping and groundwater modelling: geological observations,
conceptual understanding and hydrodynamics. Following the sequence in figure 1, geologists invest most of
their time and efforts from left to middle; whereas hydrogeologists invest most of their time and efforts from
the right to the middle.
Thus, groundwater resources investigations depend on the process of developing a conceptual flow model
as a precursor to developing a mathematical model; however in today’s work environment, this step does no
longer happen because mathematical and numerical models abound and are commercially available. Thus
the young geologists and hydrogeologists sometimes ignore this stage, or do not even know it exists in
some cases.
3D visualisation software –Platforms are readily available:
To facilitate the development of the conceptual model
To make the model more robust and defensible
To assist in demonstrating the hydraulics of the aquifer system
A few of the state-of-the art platforms are: VULCAN (Australia) –mining; EARTHVISION (Dynamics
Graphics, California)- reservoir characterization, oil, gas, groundwater remediation, etc.; GoCAD (Earth
Decision Sciences, France)- mining, oil, etc.; and MAGICS (Colenco, Switzerland) - radioactive wastes,
hydrogeology. All four platforms are commercially available.
3. APPROACHES TO GROUNDWATER MODELLING
Hydrogeological modelling requires numerical methods to provide both a suitable representation of the
subsurface and an adequate base for the simulation of flow and transport processes required for
environmental studies (water resources, climate change). As a prerequisite to building a (numerical)
geological model, it is necessary first to generate a conceptual model. This conceptual model combines data
and knowledge from various disciplines concerning geometry, geology, physical parameters and processes
of interest. This process however should be iterative; the conceptual model should be updated as additional
environmental, geologic and hydrogeologic studies, as well as simulations with the original model, provide
new data and new understanding of the groundwater flow systems.
3.1 Types of approaches, models
The flow of groundwater through rock is normally modeled using one of two types of models. If the length
scale of interest is large compared with the scale of heterogeneities, such as fracture lengths, then an
equivalent porous medium (EPM) approximation can be used. In this case, properties such as hydraulic
conductivity are averaged over appropriate rock volumes. This is the most common approach still used
today. In Canada, even though most of the aquifers are in fractured media, the EPM approach has been
systematically used for groundwater resources research; see section below. This is an area where
groundwater modelers need additional support from the geological modelers to decide on whether the
conceptual models of those aquifers are right and acceptable.
For fractured rock, the structure of the rock is often heterogeneous on the scale of interest. For instance, the
dominant medium for flow may be a set of large discrete fractures. In this case, the discrete fractured
network (DFN) model can be used to explicitly represent each fracture. However, it is usually impossible to
provide an exact specification for the fractured network in cases of practical interest (i.e., water resources at
regional scale) because of the complexity of the rock structure and its obvious inaccessibility. Instead, the
structure of the rock is described in terms of the statistics of the fracture sets, such as the fracture density
and orientation. A stochastic approach is then used to generate a number of independent realizations of the
fracture system.
Figure 2 ConnectFlow model with a porous medium representation of the near surface
and a fractured basement (Serco, 2000)
A combination of the two approaches described above (EPM and DFN) is possible and has been utilized in
the radioactive waste disposal industry. In this category, the porous media and the fracture media are
integrated into a single package that enables groundwater flow models to be constructed from sub-domains
of porous media and discrete fracture networks (Figure 2). This allows the user greater flexibility in
representing the flow in hydrogeological units. Groundwater flow is coupled across the interface between the
sub-domains by ensuring continuity of water pressures and conservation of mass at the interface. This is
possible because the conceptual model in this case is based on Darcy’s law and finite-element methods are
then used to solve the resulting partial differential equations, which in today’s advanced computer
environment is straightforward. The key of this approach however remains the model grid in the
superposition of two distinct sub-domains.
Several state-of-the-art finite-element (numerical) packages exist. Many of these have been developed by
the radioactive waste disposal and oil industries to solve problems of groundwater flow and transport using
both the porous medium approach (Nammu; Hoch, 2003); the naturally fractured reservoirs (Napsac;
Hartley, 1998); or a combination of the two (Connectflow; Serco, 2000).
3.2 Examples and approaches on groundwater models developed by the GSC
The Geological Survey of Canada (GSC) has a long history on geological mapping, in 2D, 3D, and more
recently in 3D geological modelling. 2D and 3D groundwater modelling at the GSC began to emerge a few
years before the launching of the national groundwater program in 2003. Since then, 3D groundwater
modelling has become a common practice at the GSC with groundwater models built to evaluate
groundwater resources at regional scales (>1000 km2). Table 1 shows a summary of geological and
groundwater models built over the last 10 years at the GSC.
Table 1. Groundwater models of regional-scale aquifers assessed by the GSC
Aquifer Study Type Dimensions Approach Hydrogeological
Model (HM) Does a
Geological model
(GM) exist?
Piedmont, Quebec
(1998-2001) Porous
medium 2-D, GW flow Porous MODFLOW No GM
Gulf Islands,
British Columbia
(2003-2006)
Bedrock,
fractured rock 2-D, GW flow EPM,
structural
geology
MODFLOW Yes, conceptual,
not coupled
Mirabel, Quebec
(1999-2003) Bedrock,
fractured
medium
3-D EPM FEFLOW
(Nastev et al,
2005)
Yes, goCAD, but
not coupled, built
after HM
(Ross et al, 2005)
Oak Ridges
Moraine, Ontario
(1999-2003)
Porous 3-D, GW flow Porous MODFLOW Yes, very detailed
but not coupled
Carboniferous
Basin, New
Brunswick
(2000-2003)
Bedrock,
fractured
medium
3-D GW flow EPM MODFLOW No GM
Winnipeg aquifer,
Manitoba (1999-
2003)
Bedrock,
fractured
medium
3-D, GW flow
and transport EPM 3DFRACV
(Kennedy, 2003) GM only, not
conceptual GM
Annapolis, Nova
Scotia (2003-
2006)
Combined
porous-
fractured
media
3-D GW flow EPM FEFLOW No GM
Châteauguay,
Quebec
(2003-2006)
Bedrock,
fractured rock 3-D GW flow EPM FEFLOW
(Lavigne, 2006) Yes, but not
coupled, built
after HM
St.-Mathieu Esker,
Quebec (2003-
2006)
Porous 3-D, GW flow Porous MODFLOW
(Riverin et al,
2005)
Yes, SVM, but
built after HG
(Smirnoff et al, in
press)
Okanagan, British
Columbia
(2003-2009)
Combined
porous-
fractured
media
3-D, GW flow EPM Planned Partially, only the
surficial aquifer
(planned)
Paskapoo, Alberta
(2003-2009) Bedrock,
fractured rock 3-D, GW flow Combined
EPM/DFN
(planned)
Planned Planned
As can be seen from table 1, very few of the groundwater models originally had a geological model.
Furthermore, even if the majority of the regional-scale aquifers modelled by the GSC are on fractured media,
none used the DFN approach. The Paskapoo system in Alberta will attempt to use a combined EPM/DFN
approach for the first time.
4. GROUNDWATER ANALYSIS & SIMULATION TYPES
There are several approaches to modelling the hydrodynamics of groundwater. For instance, the state of
groundwater fluctuations and their causes may be assessed with:
Statistical analysis (e.g., time-series analysis);
Geostatistical conditioned simulations (e.g., correlation); or
Deterministic analysis (e.g., numerical models).
The first two approaches above are not physically-based; they do not distinguish “the causes”. The third
uses the cause-effect principle and separates the influence of humans and that of nature. These approaches
are increasingly being applied under the context of climate change impacts on water resources, and will
likely be integrated into geological/hydrogeological modelling platforms in the coming years.
Given the many issues around groundwater resources that have emerged in the last 20 years, we see two
different “schools” of groundwater scientists developing the multidisciplinary science of hydrogeology:
fundamental hydrogeologists and environmental hydrogeologists. Fundamental hydrogeologists study and
develop laws and methods to quantify groundwater flow from a theoretical perspective. Environmental
hydrogeologists use those laws and methods to study real aquifer systems, that is, geological formations
containing and conducting water. The second group is the one that most closely interacts with geologists.
Environmental hydrogeologists develop and apply models where groundwater interacts with rocks, rivers,
lakes, ecosystems, land uses, etc. For instance, this group must monitor that groundwater exploitation is
kept within a sustainable use and must provide a clear path of potential contaminants underground. The
challenges for this group of scientists are too many: how to integrate too much existing data and
knowledge? How to deal with so many expertises involved? The current international practices for water
resources management (IWRM), for instance, represents a huge challenge for this group. The IWRM
approach requires the building of an integrated water-resources model which includes the aquifer in relation
with the geology of a watershed, interactions with surface water (rivers, lakes, wetlands), land use practices
(agriculture, urbanization) and most recently, elements to evaluate climate change impacts.
We can group the types of current and future environmental (groundwater) models into four broad
categories: independent, coupled, semi-integrated and fully-integrated models. Table 2 shows these with
their current state, associated uncertainties and applications.
Table 2. Types of environmental (water) models.
Category Current state Application
Separated models
Meteorological
Hydrological
Hydrogeological
High uncertainties
Mid uncertainties
Mid uncertainties
Climate predictions
Surface water resources
Groundwater resources and contaminant
transport
Coupled models
Meteorological-
hydrological
Hydrological-
hydrogeological
High uncertainties
Mid uncertainties
Watershed analysis and IWRM
IWRM and Climate Change
Semi-integrated models
Hydrodynamic
Watershed dynamics
Watershed management
On-going research still
many uncertainties
Resource management
Watershed without groundwater, and
without management
Watershed with groundwater, without
management
Fully-integrated models
Coupled meteorological-
hydrological-
hydrogeological
Category of the future,
still containing high
uncertainties
For climate change scenarios coupling climate,
surface water and groundwater (i.e.,
HydroGeoSphere, Therrien, et al., 2004)
5. TOWARDS AN INTEGRATED HYDROGEOLOGICAL APPROACH
During the past few decades, computer models for simulating groundwater systems have played an
increasing role in the evaluation of groundwater development and management alternatives. Groundwater
modeling serves as a quantitative means of evaluating the water balance of an aquifer, as it is affected by
land use, climate, and groundwater withdrawals, and how these changes affect streamflow, lake levels,
water quality, and other important variables. The trends in future developments clearly indicate the
integration of disciplines and processes.
Most developments have been done more or less in an isolated way. We’ve seen that good platforms for
geological modelling exist, as well as excellent numerical tools for solving groundwater dynamics. However,
there is no such an integrated platform to include pre-processors, simulators and post-processors to build
geological models and simulate the hydrodynamics of groundwater. It is still rare to find a computer
environment in any given research institute where all these three processes are integrated and available to
hydrogeologists. Figure 3 displays such an environment.
Pre-processors include information from GIS (MAPINFO) and are used to facilitate data synthesis, analysis,
and visualization. Data layers can include hydrologic, geologic and hydrogeological maps. Information form
geological models may be retrieved from these grids created in this stage (GoCad). When working with
fractured media and using the DFN approach, geostatistical modelling and upscaling is done in this stage
(ISATIS). It is in this stage where geologists and hydrogeologists should work closely and produce a
comprehensive conceptual model of the groundwater flow system they wish to simulate. A graphical user
interface (GUI) has become a necessity; it is a type of user interface which allows people to interact with a
computer and computer-controlled devices which employ graphical icons, visual indicators or special
graphical elements called "widgets", to represent the information and actions available to a user. The GUIs
are the future in integrated hydrogeological modelling using modelling geomatics and expert systems. This
stage may include any numerical simulator available coupled to the mesh created in the previous stage. The
state-of-the art in these type of interfaces (grid-to-numerical solvers) is the ESRI approach using the object-
oriented architecture using geometric objects to represent both model meshes and physical parameters
associated with those models (Heinzer and Williams 2005). The hydrodynamics to solve for in this stage
may include any variable of the flow and transport systems, pressure, concentration, heat, compaction, etc.
Figure 3. Integrated system to build, simulate and display groundwater models
The third phase, post-processing, has become perhaps the most important part of the modelling process.
Due to the many factors involved in environmental hydrogeology (see section 4) there is strong need for
understanding groundwater from water managers and public at large, thus visualization is a key element in
modelling. In the future we should be able to virtually “walk” the client through and inside the simulated
aquifer. In this phase, GIS plays an important role too. For instance, the interface linking meshes to the
solvers can once more be used in this phase allowing direct visualization of the results in the viewer. This
area has not received the attention it deserves in the hydrogeological community other than the radwaste
industry. Hydrogeologists dealing with water resources should include and use this phase more often to
promote and educate groundwater flow system and interactions in the geosphere and biosphere. For
instance, 3D visualization usually improves understanding and interpretation of huge quantities of simulation
data, which may not be visually attractive, nor understood, in other graphical forms.
An additional difficulty in such a platform is the communication between blocks (data transfer), in particular,
between pre-processors and simulators due to different types of grids, regular to semi-regular, etc. A case in
point can be cited here regarding one of the GSC modeling projects where GoCad was used to build the
geological model and FEFLWO to build the hydrogeological model. Problems with the transfer of model
parameters from GoCad to FEFLOW for instance could not be resolved during the time allocated to the
study (Ross et al, 2005).
The platform for an integrated system shown in figure 3 includes some commercially-available software
packages which can do more than others in the same category. For example, GoCad does all kinds of
statistics and data management, while the SVM can only be used as a powerful classifier. Others (e.g.,
MAGICS) are mostly mesh generators with no simulation capabilities. Thus, the outputs from the pre-
processors may be used as intermediate “inputs” to simulators depending on the problem to solve, such as
3D meshes, classified geological units, realization of lithofacies, etc. Likewise, some simulators can perform
pre-processing tasks too (e.g. FEFLOW).
6. CONCLUSION
Increased emphasis in geological mapping and groundwater applications is observed in interrelated
disciplines of Earth sciences, yet a clear link between geological mappers and groundwater modelers is still
lacking. More serious efforts are needed in three disciplines: geology, hydrogeology and geomatics when
dealing with groundwater models. Some of the most important issues on the differences between these
practitioners are that hydrogeological models have a very different nomenclature (ontology) than geological
models. Thus, there is a need for a much deeper communication between these interrelated disciplines.
Technology and tools abound but these practitioners do not take full advantage to benefit each other.
Integrated and automated platforms for modelling 3D processes in hydrogeology using experts systems and
standard ontologies are the future and should be pursued in close cooperation between the three domains.
REFERENCES
Hartley, L.J., 1998. NAPSAC (Release 4.1) Technical Summary document AEA AEA-D&R-0271.
Heinzer, T. and D. Williams, 2005. Applied Research in ArcObjects-based Hydrodynamic Analysis.
Hoch, A.R. 2003. NAMMU (Release 7.2) Command Reference Manual, Serco Assurance Report SA/ENV-
0628, 2003.
Kennedy, P. 2003. Groundwater flow and transport model of the red river/interlake area in southern
manitoba.” Ph.D. thesis, Department of Civil Engineering, University of Manitoba.
Lavigne, M.-A., 2006. Modélisation numérique de l'écoulement régional de l'eau souterraine dans le bassin
versant de la rivière Châteauguay. M.Sc. Thesis, Institut National de la Recherche Scientifique -
Eau, Terre et Environnement, Québec.
Nastev, M., Rivera, A. Lefébvre, R. and Savard, M. 2005. Numerical simulation of regional flow in
sedimentary rock aquifers. Hydrogeology Journal, 13(4): 544-554.
Riverin, M-N., Lefebvre, R., Bolduc, A., Paradis, S.J. , Paradis, D., 2005. Characterization and modelling of
flow dynamics in the Saint-Mathieu/Berry esker, Abitibi, Québec, Proceedings of the 58th Canadian
Geotechnical Society and 6t, p.1-8
Ross, M., Parent, M. and Lefebvre, R. 2005. 3D geologic framework models for regional hydrogeology and
land-use management: a case study from a Quaternary basin of southwestern Quebec, Canada.
Hydrogeology Journal, vol. 13, p. 690-707.
Serco, 2000. ConnectFlow (Release 9.4) - Technical Summary Document, Serco Assurance Ltd.
Therrien, R., McLaren, R.G., Sudicky, E.A., and Panday, S.M. 2004. HydroGeoSphere: A Three-dimensional
Numerical Models Describing Fully Integrated Subsurface and Surface Flow and Solute Transport,
Manual (Draft), HydroGeoLogic Inc., Herndon, VA.
Smirnoff, A., Boisvert, E., and Paradis, S.J., in press. Support Vector Machine for 3D modelling from sparse
geological information of various origins: Computers & Geosciences (2007).
... nd mass transport. Therefore, the quality of numerical modelling outputs largely depends on the stratigraphic and sedimentologic knowledge and on its integration in numerical models (Ross et al., 2004). In addition, simulation results need to be presented visually and in a meaningful way to water managers, decision makers and to the general public. Rivera (2007) described an integrated hydrogeological modelling system as a combination of three major components: 1) Pre-Processors, 2) Simulators and 3) Post-Processors (Figure 1). While at every level, a number of powerful software solutions exist, there is no single, fully-integrated system that would incorporate all of the above components. Soft ...
... While at every level, a number of powerful software solutions exist, there is no single, fully-integrated system that would incorporate all of the above components. Software interplay between Pre- Processors and Simulators is particularly challenging (Rivera, 2007). As pointed out by Ross et al. (2005a), improving interoperability between geological and groundwater modelling environments must be undertaken as the next immediate step to improving integration of geological information into hydrogeological models. ...
Article
Full-text available
Property transfer from geological to hydrogeological models is an important step in setting initial conditions for groundwater flow simulation. However, most mainstream software packages still do not possess built-in utilities for this procedure. While software engineers are looking for integrated commercial solutions, some simple stand-alone tools can provide the necessary link. We developed GOFEFLOW, an in-house tool for property transfer from a gOcad ® geological model to a mesh of triangular prisms generated in FEFLOW ® . Here we describe the tool and demonstrate its application in a hydrogeological modelling project. RÉSUMÉ Le transfert des propriétés géologiques à un modèle hydrogéologique est très important pour mettre en place les conditions initiales de simulation de l'écoulement des eaux souterraines. Cependant, très peu de logiciels commerciaux, à notre connaissance, possèdent un module permettant d'effectuer cette opération. Pendant que les ingénieurs informatiques cherchent des solutions intégrées, un simple outil utilitaire qui permet le transfert des propriétés a été développé. Nous avons créé GOFEFLOW, un utilitaire qui permet de transférer les propriétés d'un modèle géologique gOcad ® à un maillage de prismes triangulés généré par FEFLOW ® . Dans cet article, nous présentons l'outil et son application à un cas réel.
... 2D and 3D groundwater modelling at the GSC began to emerge a few years before the launching of the national groundwater program in 2003. With strong collaboration with provincial agencies and universities, the GSC has built several three-dimensional regional-scale (>1000 km 2 ) geological and h ydrogeological models across the country (Rivera, 2007). Numeric groundwater flow modelling has ranged from regional 3-D numeric models constructed in MODFLOW and FEFLOW (e.g. ...
Article
Full-text available
The Geological Survey of Canada (GSC) is helping map and assess the availability of groundwater resources in Canada. This effort is set within complex jurisdictions of surface water and groundwater resources in Canada where there is often no clear division between the federal and provincial governments. Responsibilities are often shared, with the federal government sharing responsibility on water issues for federal lands, territories (e.g. Nunavut), First Nation lands, boundary and transboundary waters (e.g. Great Lakes, Spiritwood aquifer), navigable waterways and where fisheries resources are concerned. Consequently, much government work completed on groundwater in Canada is done by the provinces with collaborative support from the GSC, the oldest government research institution in the country. To advance groundwater assessment in Canada, the National Ad Hoc Committee on Groundwater proposed a framework for a national co-operative program (Rivera et al., 2003). At the same time, the groundwater program of the GSC developed a strategy to map and assess 30 key aquifers across the country (Figure 1), along with a plan to remove accessibility barriers to data discovery and retrieval (Boisvert and Broderic, 2011). The GSC is also developing a synoptic understanding of the groundwater resources in Canada by using the hydrogeological regions (Figure 1, Table 1). This paper provides an overview of the conceptual framework and methods employed to achieve these objectives. The approach is founded on a traditional basin analysis methodology (i.e., geology) with an objective of understanding the geological history of the basin to inform future work and provide a predictive framework in areas of sparse, inadequate data and hence basin knowledge. This approach is being extended from the traditional subsurface basin context to encompass the hydrological cycle and hence understanding from atmosphere to basement.
Article
Full-text available
Purpose – The purpose of this paper is to develop a three dimensional (3D) geological model, based on geographic information system (GIS), of the Barwon Downs Graben aquifer system in Victoria, Australia, and to visualize the complex geometry as a decision support tool for sustainable water management. Design/methodology/approach – A 3D visualization of the aquifer is completed, based on subsurface geological modelling. The existing borehole database, hydrogeological data, geological information and surface topography are used to model the subsurface aquifer. ArcGIS 9.2 is employed for two‐dimensional (2D) GIS analysis and for 3D visualization and modelling geological objects computer aided design (GOCAD) 2.5.2 is used. The developed methodology of ArcGIS and GOCAD is implemented for creating the 3D geological model of the aquifer system. Findings – The 3D geomodel of the Barwon Downs Graben provides a new perspective of the complex subsurface aquifer geometry and its relation with surface hydrogeology in a more interactive manner. Considering the geometry, estimated volume of the unconfined Eastern View aquifer is as 0.83 × 10¹⁰ m³ and for the confined aquifer is about 1.02 × 10¹⁰ m³. The total volume of overlying strata of this aquifer is about 3.0⁹ × 10¹⁰ m³. The water resources of the study area are affected by the pumping from this aquifer. This is also significantly influenced by the geometry of the Graben. Originality/value – The 3D model utilises comprehensive and generally available datasets in the public domain. Although the used 3D geomodelling tools are mainly developed for applications in the petroleum industry, the current paper shows its ability to be adapted to hydrogeological investigations.
Article
Full-text available
The St. Lawrence Lowlands platform, Quebec, Canada, is a densely-populated area, heavily dependent on groundwater resources. In 1999, the Geological Survey of Canada initiated a large-scale hydrogeological assessment study over a 1,500km2 region northwest of Montreal. The objectives were to define the regional groundwater flow, and to give quantitative estimates of the groundwater dynamic parameters and of the available groundwater resources. The applied approach consisted of defining the hydrogeologic framework, hydraulic properties of the aquifer units, and groundwater dynamic components. Lower Paleozoic sedimentary rocks represent regional aquifer units. Coarse Quaternary fluvio-glacial sediments locally overlay the rock sequence and constitute an interface aquifer unit. Fine marine sediments confine most of the regional aquifers. Collected GIS based information was synthesized in a finite element numerical model. The regional saturated steady-state flow was calibrated under current stress conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow in regional aquifers amounts to 97.7Mm3/y. Infiltration from precipitation provides 86.6% of the groundwater supply, while 9.6% comes from subsurface inflow and the remaining 3.8% is induced recharge from surface waters. Discharge from regional aquifers occurs through flow to streams (76.9%), groundwater withdrawal (18.4%), and underground outflow (4.7%).
Article
Full-text available
During a regional hydrogeologic survey in the St. Lawrence Lowlands, Canada, a computer-based 3D Geologic Framework Model (GFM) was constructed to obtain a consistent representation of this typical Quaternary glaciated basin over a 1,400 km(2) area. Such a detailed stratigraphic reconstruction was needed because the Quaternary sediments control the recharge to the underlying regional fractured rock aquifer and also because buried granular aquifers are partly connected to the regional system. The objectives of this geomodeling effort are 1) to improve understanding of subsurface conditions above the regional aquifer and; 2) to provide a common stratigraphic framework for hydrogeologic applications. The method draws on knowledge-driven discrete modeling using gOcad, as well as standardization and quality control procedures to maximize the use of a multisource database. The resulting model represents the bedrock topography and the complex stratigraphic architecture of overlying sediments. The regional till aquitard, the marine clay aquiclude and the buried granular aquifers have been modeled with unprecedented details thus providing a well-constrained 3D hydrostratigraphic framework. The recharge zones of the rock aquifer represent about 35% of the study area. Buried granular aquifers are directly connected to the regional aquifer system over about 10% of the area. The model allows several applications such as assessing aquifer vulnerability and areal groundwater recharge rates; improving the GFM inter-operability with groundwater modeling systems would be the next logical step.
Article
ABSTRACT NAPSAC is a software package to model,flo w and transport through frac- tured rock. The models,are based on a direct representation of the discrete fractures making up the flo w conducting network. NAPSAC uses a stochas- tic approach,to generate networks of planes that have the same,statistical properties as those that are measured,for fractures in fieldexperiments. The software is based,on a very efficientfinite-elementmethod,that allows the flo w through many thousands,of fractures to be calculated accurately. This Technical Summary Document,provides a list of the current capabilities of the program and a description of the numerical methods,used. AEA Technology
Article
This paper presents an overview of some of the research performed at the Bureau of Reclamation, Mid-Pacific GIS Service Center over the past two years related to the application of ArcObjects technology involving hydrodynamic modeling. Topics include finite element mesh generation and the representation of mesh components as a geometric network, construction of 3D fence diagrams in applications using the HydroGeoSphere model, and interface development between ArcGIS and various hydrodynamic models.
Article
Thesis (Ph. D.)--University of Manitoba, 2003. Includes bibliographical references.
HydroGeoSphere: A Three-dimensional Numerical Models Describing Fully Integrated Subsurface and Surface Flow and Solute Transport, Manual (Draft), HydroGeoLogic Inc Support Vector Machine for 3D modelling from sparse geological information of various origins
  • R Therrien
  • R G Mclaren
  • E A Sudicky
  • S M Panday
  • Va Herndon
  • A Smirnoff
  • E Boisvert
  • S J Paradis
Therrien, R., McLaren, R.G., Sudicky, E.A., and Panday, S.M. 2004. HydroGeoSphere: A Three-dimensional Numerical Models Describing Fully Integrated Subsurface and Surface Flow and Solute Transport, Manual (Draft), HydroGeoLogic Inc., Herndon, VA. Smirnoff, A., Boisvert, E., and Paradis, S.J., in press. Support Vector Machine for 3D modelling from sparse geological information of various origins: Computers & Geosciences (2007).
Numerical simulation of regional flow in sedimentary rock aquifers
  • M Nastev
  • A Rivera
  • R Lefébvre
  • M Savard
Nastev, M., Rivera, A. Lefébvre, R. and Savard, M. 2005. Numerical simulation of regional flow in sedimentary rock aquifers. Hydrogeology Journal, 13(4): 544-554
Modélisation numérique de l'écoulement régional de l'eau souterraine dans le bassin versant de la rivière Châteauguay
  • M.-A Lavigne
Lavigne, M.-A., 2006. Modélisation numérique de l'écoulement régional de l'eau souterraine dans le bassin versant de la rivière Châteauguay. M.Sc. Thesis, Institut National de la Recherche Scientifique -Eau, Terre et Environnement, Québec.
Characterization and modelling of flow dynamics in the Saint-Mathieu/Berry esker, Abitibi, Québec, Proceedings of the 58th Canadian Geotechnical Society and 6t 3D geologic framework models for regional hydrogeology and land-use management: a case study from a Quaternary basin of southwestern Quebec
  • M Riverin
  • N Lefebvre
  • R Bolduc
  • A Paradis
  • S J Paradis
Riverin, M-N., Lefebvre, R., Bolduc, A., Paradis, S.J. , Paradis, D., 2005. Characterization and modelling of flow dynamics in the Saint-Mathieu/Berry esker, Abitibi, Québec, Proceedings of the 58th Canadian Geotechnical Society and 6t, p.1-8 Ross, M., Parent, M. and Lefebvre, R. 2005. 3D geologic framework models for regional hydrogeology and land-use management: a case study from a Quaternary basin of southwestern Quebec, Canada. Hydrogeology Journal, vol. 13, p. 690-707