Presentation by Jan Gunnink (TNO) at the iMOD International User Day, during Delft Software Days 2016. Tuesday 1 November 2016, Delft.

1. Geo-modelling (with iMOD) at the Geological Survey
of the Netherlands
Jan L. Gunnink
Geological Survey of the Netherlands - TNO

2. Dutch subsurface
in the deep subsurface
… we make money
in the shallow subsurface
… we avoid costs
Foundation

3. 2
. 40% of the country is below Mean Sea Level
. Groundwater and Subsidence are major issues
Geology of shallow sub-surface
determines impact of:
-Climate change
-Infrastructure
-Urban development
-Salinization

4. Geological Survey of the Netherlands
Maintaining database with:
- > 450000 boreholes
- geophysical data (seismics, electromagnetics)
- Cone Penetration Tests (CPT)
- groundwater (heads & quality)
Geological and geohydrological models: DGM/Regis/GeoTOP
Developing new techniques for data-assimilation
3

5. core assets
DINO (national data repository)
borehole data
geophysical and geochemical data
models (interpretations  predictions)
national coverage, high data density
own and third-party data
standardized
freely accessible

6. Geological Survey
of the Netherlands - TNO
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nation-wide models (~41,000 km2)
Layer-based: top and base
Basic attributes:
- Geological Formation / Member
- aquifer / aquitard

7. Voxel models
upper 30 m
resolution 100 x 100 x 0.5 m
each voxel contains:
stratigraphic unit + uncertainty
lithology (sand, clay, peat) + uncertainty
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Anthropogenic
Clay
Peat
Fine sand
Medium sand
Coarse sand
Clayey sand

8. 7
Use of iMOD:
- Cross-section to check results of modelling

9. 8
3D view for inspection of the model

10. 9
Combining layer and voxel models to check consistency between models

11. 10
3D viewing of large voxel models “on the fly”

12. Parameterization of Voxel models
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Stratigraphy
Lithology and sand grain-size
Hydraulic conductivity
Groundwater
flow models
+

13. Measuring hydraulic conductivity
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How?
Measure from samples
Pumping tests
Slug tests
Empirical relationships linking
lithology and grain-size to
conductivity

14. Measuring hydraulic conductivity
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Systematic sampling of
stratigraphic units and
lithologies in the Netherlands

15. Scale difference between measurement and
model
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100 m
0.1 m

16. Small-scale heterogeneity
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0.1 m
Alternating sand and clay
layers in a tidal environment
low high
Hydraulic conductivity (m/day)
1 m

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5 * 50
distributions
of vertical
hydraulic
conductivity
Block composed
of small voxels of
0.5 x 0.5 x 0.05 m
Effective vertical
hydraulic
conductivity of
the entire block
(m/day)
Apply flow-model: upscaling in iMOD
Vertical flow

18. 14-11-16 10:20
Titel van de presentatie
17

19. 18

20. Results
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Clay
Sand
N=50
Effective vertical hydraulic conductivity
of a heterogeneous sand-clay voxel
40%
60%
0.1 m
0.1 m
1 m

21. Application: hydraulic resistance map
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70 km
days
Calculated from upscaled
hydraulic resistance

22. Conclusions
Geological modelling is done at a nation-wide scale at the Geological
Survey
Inspection of modelling results, layer and voxel models, is easy done
in iMOD
Large datasets can be handled efficiently
Upscaling routines are available to assign representative hydraulic
conductivities to voxel models
Cooperation with iMOD team (developers, support) results in prompt
and easy interaction
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