3D models of sedimentary lithologies and
piezometric levels to understand
groundwater and surface water flows, Wairau
Plains, New Zealand
… and web-based access to 3D model data
P. White
C. Tschritter
P. Davidson
GNS Science
GNS Science
Marlborough District Council
GNS Science
Acknowledgements
Thanks to:
• Harvey Thorleifson for the invitation to present this talk
• GNS Science Groundwater Resources Research Programme
for 3D model development (Wairau Plains) and GNS ‘seed’
funding (web site).
• Groundwater managers for in-kind and direct support on
model development, particularly Marlborough District
Council and Bay of Plenty Regional Council (Janine Barber)
GNS Science
Outline of the talk
Methods
3D models of geology and groundwater level: example of Wairau Plains
Web-based access to model data
• Web site demo
Software used in talk: Earthvision and home-built including web and FORTRAN
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Methods
Building 3D geological models: two main types
•
Lithology (3D)
These models are used to understand the distribution of
sediments relevant to aquifers systems and are
particularly useful when interpreting drillers’ logs
• Chrono – stratigraphic (typically 2D surfaces)
These models aim to understand strata in relation to time
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Lithological models: a statistical approach with
geological logs
Useful because we are uncertain
about the quality of well logs
We use ‘pseudo-logs’
e.g. blue = water bearing
pink = other
The 3D model itself has an important
role in data-quality checking
Reference: White, P.A. and Reeves, R.R. 1999. Waimea Plains
aquifer structure as determined by three-dimensional computer
modelling. Journal of Hydrology (NZ) 38 (1) 49-75.
Well log and pseudo log
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Lithological models: a statistical approach with
geological logs
1) Well log data quality checks
2) Pseudo-logs are plotted in 3D space
3) …and then modelled as continuous
distribution in 3D as 3D grid and 3D ‘faces’
file
4) Models developed separately for:
gravel;
sand;
silt and clay.
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3D models of static groundwater level in 3D
1) Quality checks of static groundwater level data (e.g. remove
wells where level is influenced by pumping)
2) Assemble as 3D points
3) Model as continuous 3D distribution in a conformal grid
Unconfined area
Confined area
Holocene Gravel
aquifer
Static groundwater level (colour) and elevation of the base of the
screen.
Holocene/
Pleistocene
Gravel aquifer
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Web site access to model data
Aim: access to 3D model data for everybody, e.g.:
•
•
•
•
•
education (e.g., children)
drillers
groundwater managers
Scientists
general public
Some criteria:
•
•
•
•
•
not dependent of proprietary software
intuitive
fast
access to models from the field (i.e., smart phones)
uncertainty
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An example of 3D models: Wairau Plain
One purpose of this work: how does groundwater
recharge travel to spring-fed streams?
•
Important to water management in the area
The following slides show the results of:
•
•
•
Development of 3D models (geology and piezometric level)
Comparison of 3D geology and 3D piezometric level
Groundwater budget
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Wairau Plain
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Wairau Plain geology and historic hydrology
Yellow = alluvial in west
marine/estuarine in east
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Study area:
1165 geological logs
1562 static water level measurements
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Results: 3D geological model: combines
chrono- and lithology models
Main purpose is to assess the distribution of Holocene gravels, sands and
silts/clay
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Results: 3D piezometric model and 2D water
table
Piezo contours in 2D
Piezo contours in 3D
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Results: 3D geological model, piezometric
model and groundwater budget
Groundwater budget zone
West of
Budget component
East of
transition
Transition
(m3/s)
P
transition
(m3/s)
(m3/s)
1.6
1.2
1.5
QGWIN (Wairau River)
7
0
0
QGWIN (other rivers)
1
0
0
0.1
8.1
0.8
ET
-1.4
-1.1
-1.4
UGW (irrigation)
-0.2
-0.2
-0.3
UGW (municipal)
0
-0.1
0
QSWBF
0
-7.1
-0.5
-8.1
-0.8
-0.1
Inflow
QGWIN (boundary)
Outflow
QGWOUT (boundary)
West – east sections
Approx 90% of nett gw inflow (Transition zone
and west) flows to spring-fed streams
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Web-based access to model data
Aims to provide model information to
anyone
http://data.gns.cri.nz/ebof/
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Web access to model data:
Aims to provide model information to anyone
GNS Science has a programme of sub-regional 3D
model development
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Earth Beneath Our Feet web site:
Aim to represent:
Layers
Properties
and uncertainty
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Conclusions
3D models
•
Models of lithology, chrono-stratigraphic units, when combined with
models of static groundwater levels are very useful in understanding
coastal aquifer systems
•
These models shown that most groundwater recharge in the
Transition zone and west (approx 90%) flows to springs
•
This has significant implications for management of the system
Web-based access to model information
•
•
shown to be great fun
… and it’s useful for groundwater managers
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Thanks very much
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