Earth Sciences Sector Groundwater Mapping 1 GROUNDWATER MODELLING: FROM GEOLOGY TO HYDROGEOLOGY Alfonso Rivera Chief Hydrogeologist Geological Survey of

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Earth Sciences Sector

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GROUNDWATER MODELLING: GROUNDWATER MODELLING: FROM GEOLOGY TO HYDROGEOLOGYFROM GEOLOGY TO HYDROGEOLOGY

Alfonso Rivera

Chief HydrogeologistGeological Survey of Canada

GSA Annual MeetingDenver, CO, USA

October 28-31 2007

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GROUNDWATER MODELLING: GROUNDWATER MODELLING: FROM GEOLOGY TO HYDROGEOLOGYFROM GEOLOGY TO HYDROGEOLOGY

OUTLINEOUTLINE• Modelling

• Geology mapping-Groundwater modelling links

• Approaches to Groundwater Modelling

• Examples of Models developed by the GSC

• Groundwater Analysis & Simulation types

• Towards an integrated hydrogeological approach

• Summary and Conclusions

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MODELLINGMODELLING

So what do we mean?

Modelling is a very broad term; we have:

• Geological Models • Conceptual Models • Hydrogeological models• Mathematical models• Analytical models• Numerical models• Deterministic models• Stochastic models• …

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Geology Mapping-Groundwater Geology Mapping-Groundwater Modelling LinksModelling Links

• Groundwater investigations depend on the process of developing a conceptual flow model as a precursor to developing a mathematical model

• … leading to the development of a numerical approximation model

• Assumptions made in the development of the conceptual model depend heavily on the geological framework (or model) defining the aquifer

Thus, the link between geological mapping and groundwaterModelling is the building of a conceptual model

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Geology Mapping-Groundwater Geology Mapping-Groundwater Modelling LinksModelling Links

Conceptual ModelConceptual Model

Geologist

Hydrogeologist

Geological surveyGeological survey Hydrogeological modelHydrogeological model

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Define Objective

Conceptual Model

Mathematical Model

Numerical Formulation

Computer Program

Analytical Solution

Model design

Calibration

Verification

Prediction

Presentation of results

Postaudit

Code verified? no

yes

Code Solution

Field data

Field data

Comparison with

Field Data

Pre-Processing

Modelling/Simulation

Post-Processing

Overview of the Hydrogeological Overview of the Hydrogeological Modelling ProcessModelling Process

Geological m

odel

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Approaches to Groundwater Approaches to Groundwater ModellingModelling

The flow of GW through fractured rock aquifers is modelled using one of two types of conceptual models:

Equivalent Porous Medium (EPM)If the length scale of interest is large compared with the

scale of heterogeneities, such as fracture lengths

Discrete Fractured Network (DFN)When the structure of the rock is highly heterogeneous

on the scale of interestThe structure of the rock is described in terms of

statistics of the fracture sets, i.e., fracture density and orientation

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Types of approaches, models

• Equivalent Porous Medium (EPM)• Discrete Fractured Network (DFN)• A combination of the two

(Serco, 2000)

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Example of Methodology for Example of Methodology for Developing Conceptual and Developing Conceptual and

numerical modelsnumerical models

(Rivera et al., 2001)

GG GG

GG

HgHg

HgHg HgHgHgHgG, HgG, Hg

GG GG

GG G, HgG, HgG, HgG, Hg

G, HgG, Hg

HgHg

HgHg HgHg

G, HgG, HgGG

G, HgG, Hg

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Examples of Models Examples of Models developed by the GSCdeveloped 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)


3-D GW flow EPM MODFLOW No GM

Winnipeg aquifer, Manitoba (1999-2003)


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

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Groundwater Analysis & Groundwater Analysis & Simulations TypesSimulations Types

• Two different “schools” of groundwater scientists developing the 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

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Types of Environmental Types of Environmental (water) models(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 CC

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)

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Towards an integrated Towards an integrated hydrogeological approachhydrogeological approach

GIS

Pre-Processors

Post-Processors

RASTELM MAGICS FRACMESH ISATIS GoCAD

GUI/ ESRI

Simulators :FEFLOW, SUTRA,

MODFLOW,TOUGH, etc.

TRACK AVS FED TECPLOT MATHLAB ILLUSTRATOR PHOTOSHOP

MAPINFO

P,P, C,H, T

1D2D3D

q, N t, T,Variables

SVM

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Towards an integrated Towards an integrated hydrogeological approachhydrogeological approach

• Pre-processors include information from GIS (MAPINFO) and are used to facilitate data synthesis, analysis, and visualization

• Simulators abound in the second phase, but the link with pre-procesors is still lacking to a large degree. Graphical User Interfaces (GUI) have become a necessity in this phase.

• The third phase, post-processing, has become perhaps the most important part of the modelling process, i.e.,– Strong need for understanding GW from water managers and

public, 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

• Future: integration of disciplines and processes

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Differences and Issues Differences and Issues

HM have a very differentHM have a very different ontology as compared to ontology as compared to geological geological models!models!

Model Boundary conditions:Dirichlet (specified h or c); Neumann (specified c- or q-gradients); Cauchy (combined)

Medium conditions:Heterogeneity, Isotropy, AnisotrophyPorous media, Fractured Media, discrete, EPM, Hybrid1D, 2D, 3D

Set of parameters:

Hydraulic, Transport, Mechanic, Heat: P, H, C, T, K, Ss, σ, Nα, qi, t

Type of modelling:Deterministic, stochastic

Coupling:Hydro-transport (solute transfer); Thermohaline (flow, solute, heat); Hydro-mechanic (subsidence)

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SUMMARYSUMMARY

If the geological model is wrong, the conceptual model couldbe wrong and the HG model will not be successful

• To build a HG ModelHG Model, you need:− A numerical code to solve for a set of equations− Discretization of space (FDM, FEM) and time− Boundary conditions− Initial conditions− Set of model parameters, per node, per element or

per layer− Set of data of the stresses in the system (pumping)− Set of data for calibration (heads, conc., subsidence)

We should distinguish:

Geological model --► Conceptual model --► Hydrogeological model

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SUMMARYSUMMARY

• Thus, geologists and hydrogeologists need to enhance cooperation at all levelsall levels:− Geologists need to learn to listen to hydrogeologists − Hydrogeologists need to ask geologists and learn

form their input/insight

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CONCLUSIONSCONCLUSIONS

Increased emphasis in geological mapping and groundwater applications is observed in interrelated disciplines of Earth sciences

A clear link between geological mappers and groundwater modelers is still lacking

More serious efforts of communication are needed in three interrelated disciplines: geology, hydrogeology and geomatics when dealing with GW models

Technology and tools abound but the three domains do not take full advantage to benefit each other

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CONCLUSIONSCONCLUSIONS

Most important issues: differences between practitioners, e.g., HM have a very different ontology as compared to GM

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

Documents

Earth Sciences Sector Groundwater Mapping 1 GROUNDWATER MODELLING: FROM GEOLOGY TO HYDROGEOLOGY Alfonso Rivera Chief Hydrogeologist Geological Survey of