Evaluation of Structural Uncertainty in Conceptual Hydrogeologic
Model Development
Laura Weaver1, Emmanuelle Arnaud2, Daron Abbey1, Steven Shikaze1, Beth Parker3, and Jessica Meyer3
1 AquaResource, a division of Matrix-Solutions Inc., Breslau, ON, Canada
lweaver@matrix-solutions.com
2 G360 Centre for Applied Groundwater Research, School of Environmental Sciences, University of
Guelph, Guelph, ON, Canada
3 G360 Centre for Applied Groundwater Research, School of Engineering, University of Guelph, Guelph,
ON, Canada
KEY WORDS
routine
- three-dimensional conceptual model, glacial sediments, uncertainty, interpolation
ABSTRACT
Traditionally, conceptual hydrostratigraphic framework models are developed from analyses of hydraulic head,
hydraulic conductivity, lithology, geochemistry and geophysical data derived from sparsely distributed, vertical
boreholes, in addition to other hydrogeologic data sources. These data are used to interpret depositional
environmental conditions, which guide construction of three-dimensional, conceptual model(s) that may in turn form
the basis for numerical groundwater flow modeling. The availability of sophisticated three-dimensional interpolation
software and numerical efficiency of numerical modeling codes enable parameterization and simulation of extremely
complex systems regardless of the available data. However, the increased complexity can result in significant
increases in uncertainty in the hydrogeologic framework and groundwater flow predictions where parameters are not
supported by field data. The uncertainty can be reduced by additional field data collection and constraints based on
the depositional environment(s). This paper presents a case study illustrating the influence of the use of depositional
model interpretations on the uncertainty in hydrogeologic framework models.
Three conceptual hydrogeologic block models were constructed for an unconsolidated glacial sediment system
whereby hydrogeologic unit volumes were generated using: 1) associations based on texturally similar sediment, b)
an imposed hydrostratigraphic framework on genetically-linked, texturally similar sediment (without the addition of
control points), and 3) an imposed hydrogeologic framework on genetically-linked, texturally similar sediment with the
addition of control points. The spatial distribution and interconnectedness of unconsolidated material was
interpolated across the study area from available borehole, geophysical, hydraulic test data, and other data sources
using three-dimensional interpolation algorithms in a three-dimensional software environment.
The resulting hydrogeologic unit geometries were evaluated for plausibility given the established glacial history of the
area and error associated with the interpolation. We demonstrate the effects of greater incorporation of
hydrogeologic knowledge on output sediment distributions as related to the interpolation approach and associated
structural uncertainty. This is achieved by examining modeled unit distributions and geometries, relative volumes of
hydrogeologic units, and fit of interpolation prediction between the three conceptual block models.