Spatial and temporal variability of the
unsaturated zone characterised by
geophysical and conventional
methods
H.K. French, Centre for Soil and Environmental Research (Jordforsk) Norway
A. Binley, Department of Environmental Science, Lancaster University, UK,
N.-O. Kitterød Department of Geophysics, University of Oslo
The Moreppen
research station
Oslo Airport
Gardermoen
2 km
4 km
Simulations of flow and transport based on
random fields of the permeability
Moreppen
N
p47
p45
p43
p41
10 m
Ground Penetrating Radar
p47
GPR profi
les
p45
p43
p41
top1
top2
0
depth (m)
-1
-2
dip1
dip2
-3
2
4
0
6
8
c11
c16
10
12
dry
saturated
~ 0.5 sat.
depth (m)
-1
-2
-3
2
4
6
8
10
12
2
4
6
8
10
12
0
depth (m)
-1
-2
-3
How do we characterise the
spatial variability?
• Range
• Semivariance
Soil Physical data
Time
Time
Geophysical data
Geophysical images
Which data do we use?
Sampling points,
soil physical data, vertical section
SEL2
0m
0.5 m
1.0 m
1.5 m
2.0 m
SEL3
Semivariogram analysis
From soil physical data to inverted
geophysical data
Semivariogram Angle: 0, Tolerance: 7
0.40
SEL2
Semivariance (-)
0.35
0m
0.5 m
0.30
1.0 m
0.25
1.5 m
0.20
2.0 m
0.15
0.10
Resistivity
Hydraulic conductivity
0.05
0.00
0.0
1.0
2.0
3.0
lag (m)
4.0
5.0
SEL3
Variogram analysis of resistivity
data in a horizontal plane
Distance (m)
6
5
4
3
2
1
0
0
1
2
3
4
Distance (m)
electrode @
0.2 m depth
Variogram Model
for horizontal data
Distance (m)
6
5
4
3
2
1
0
0
1
3
4
Gaussian model
Nugget: 3.25
Range: 1.27
Sill: 7.78
Distance (m)
2
Time changes in spatial structure
5.
04
11
.0
4
16
.0
4
19
.0
4
25
.0
4
30
.0
4
Dates
Nugget, sill (m^2)
70
60
50
40
30
20
10
0
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
28
.0
3
Range (m)
Gaussian model, omnidirectional
Range (m)
Nugget (m^2)
Sill (m^2)
Total Sill (m^2)
Semivariograms of resistivity and
changes in resistivity show
different behaviour
Inverted resistivities (at 0.32 m)
Ratioed inverted resistivities (at 0.32 m)
0.05
0.04
01.04_IAR
0.04
0.04
8.04_IAR
0.04
8.04_IRR
16.04_IRR
30.04_IRR
16.04_IAR
0.03
30.04_IAR
Semivariance
Semivariance
0.03
0.03
0.02
0.03
0.02
0.02
0.02
0.01
0.01
0.01
0.01
0.00
0.00
0.50
1.00
1.50
Lag distance, m
2.00
2.50
0.00
0.00
0.50
1.00
1.50
Lag distance, m
2.00
2.50
Conclusions
!
!
!
!
All methods give similar size of the range
The semivariance may vary considerably with
time, especially during snowmelt, but the
range seems to remain fairly constant
Geophysical methods may serve as a
supplementary method for characterisation of
spatial correlation structure
Electrical methods offer great potential for
characterising the dynamics of spatially
variable processes