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![Page 1: Field and laboratory experiments for parameterizing soil variables at complex tarrain Tae Hee Hwang, Seongwon Eum, and Dowon Lee Graduate School of Environmental.](https://reader036.fdocuments.net/reader036/viewer/2022062517/56649f0e5503460f94c231ee/html5/thumbnails/1.jpg)
Field and laboratory experiments for parameterizing soil variables
at complex tarrain
Tae Hee Hwang, Seongwon Eum, and Dowon Lee
Graduate School of Environmental Studies
Seoul National University
Seoul 151-742, Korea
![Page 2: Field and laboratory experiments for parameterizing soil variables at complex tarrain Tae Hee Hwang, Seongwon Eum, and Dowon Lee Graduate School of Environmental.](https://reader036.fdocuments.net/reader036/viewer/2022062517/56649f0e5503460f94c231ee/html5/thumbnails/2.jpg)
Some parameters of RHESSys are greatly variable at complex terrain.
Can we estimate the parameters from easily measurable topological indices (slope, elevation, aspect, etc.)
Introduction
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Parameters for vertical soil moisture fluxes in RHESSys
Ksat_0 : Saturated hydraulic conductivity at surface
Porosity_0 : porosity at soil surface
M_z : conductivity with actual soil depth
Porosity_decay : porosity scaling parameter with depth
Introduction
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Study Area
Gwangneung Experimental Forest, Gyonggi-do, Korea
Seoul
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Study area
Vegetation type :
deciduous broadleaf (Quercus serrata, Carpinus laxiflora community)
Elevation : 270 ~ 490 m
Avg. slope : 19.0 °
Catchment area : 22 ha
Forest age : 80 years
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Sampling points
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Field measurements
• Soil type
• Effective soil depth
• Soil color
• Slope
• Vegetation type
• Aspect
• Bedrock
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Soil type, soil depth, soil color
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![Page 10: Field and laboratory experiments for parameterizing soil variables at complex tarrain Tae Hee Hwang, Seongwon Eum, and Dowon Lee Graduate School of Environmental.](https://reader036.fdocuments.net/reader036/viewer/2022062517/56649f0e5503460f94c231ee/html5/thumbnails/10.jpg)
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Laboratory measurements• Hydraulic conductivity (L/T)
• Hydraulic conductivity decay rate with depth (1/L)
• Porosity (dimensionless)
• Porosity decay rate with depth (1/L)
• Soil texture
• Bulk density (M/L3)
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Saturated hydraulic conductivity (Ksat)
time
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Macroporosity (Φm)(pF 2.7)
pF meter DIK-3340
Daiki Co. Ltd.
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Results
0
0.02
0.04
0.06
0.08
0.1
0.12
R-
A
R-
B
R-
C
L-A
1
L-A
2
L-B
1
L-B
2
L-B
3
L-C
1
L-C
2
L-C
3
sampling sites
Ksa
t (c
m/s
ec)
A horizonsB horizons
0.20
0.25
0.30
0.35
0.40
0.45
0.50
R-
A
R-
B
R-
C
L-A
1
L-A
2
L-B
1
L-B
2
L-B
3
L-C
1
L-C
2
L-C
3
sampling s itesp
oro
sity
(d
imen
sionl
ess)
A horizons
B horizons
Ksat Φm
R, L: slope,
A: Toe, B: middle slope, C: upper slope
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ResultsKsat decay rate with depth
-1
-0.5
0
0.5
1
R-A
R-B
R-C
L-A
1
L-A
2
L-B
1
L-B
2
L-B
3
L-C
1
L-C
2
L-C
3
sampling sites
poro
sity
dec
ay r
ate
(1/m
)
-0.5
0
0.5
1
1.5
R-A
R-B
R-C
L-A
1
L-A
2
L-B
1
L-B
2
L-B
3
L-C
1
L-C
2
L-C
3
sampling sites
poro
sity
dec
ay r
ate
(1/m
)
Φm decay rate with depth
R, L: slope,
A: Toe, B: midle slope, C: upper slope
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Results
Bulk density (Db)
0
0.5
1
1.5
R-A
R-B
R-C
L-A
1
L-A
2
L-B
1
L-B
2
L-B
3
L-C
1
L-C
2
L-C
3
sampling sites
bul
k den
sity
(g/m
l)
A HorizonsB Horizons
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Correlation AnalysisΦm vs. Ksat
y = - 0.3983x + 0.1725R2 = 0.7519
0
0.02
0.04
0.06
0.08
0.1
0.12
0.0 0.1 0.2 0.3 0.4 0.5
porosity
Ksa
t (c
m/s
ec)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.0 0.1 0.2 0.3 0.4 0.5
porosity
Ksa
t (c
m/s
ec)
A Horizons B Horizons
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Correlation Analysis with Topological Index (Slope)
Slope vs. Ksat
0
0.02
0.04
0.06
0.08
0.1
0.12
0 5 10 15 20 25
slope (degree)
Ksa
t (c
m/s
ec)
0
0.02
0.04
0.06
0.08
0.1
0.12
0 5 10 15 20 25
slope (degree)
Ksa
t (c
m/s
ec)
A Horizons B Horizons
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Correlation Analysis with Topological Index (Slope)
Slope vs. Φm
A Horizons B Horizons
y = 0.0057x + 0.2548
R2 = 0.5368
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0 5 10 15 20 25
slope (degree)
Po
rosi
ty
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0 5 10 15 20 25
slope (degree)
Po
rosi
ty
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Correlation Analysis with Topological Index (Slope)
Slope vs. Φm decay rate Slope vs. Ksat decay rate
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25
slope (degrees)
Ksa
t d
ecay
rat
e (1
/m)
0
0.1
0.2
0.3
0.4
0.5
0.6
0 5 10 15 20 25
slope (degrees)
po
rosi
ty d
ecay
rat
e (1
/m)
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Correlation Analysis with Topological Index (Elevation)
Elevation vs. Ksat Elevation vs. Φm
0
0.02
0.04
0.06
0.08
0.1
0.12
300 350 400 450
slope (degree)
Ksa
t (c
m/s
ec)
Elevation vs. Porosity (A)
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
300 350 400 450
slope (degree)
Ksa
t (c
m/s
ec)
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Correlation Analysis with Topological Index (Elevation)
Elevation vs. Φm decay rate Elevation vs. Ksat decay rate
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500
Elevation (m)
Ksa
t d
ecay
rat
e (1
/m)
0
0.1
0.2
0.3
0.4
0.5
0.6
0 100 200 300 400 500
Elevation (m)
Ksa
t d
ecay
rat
e (1
/m)
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Correlation Analysis with Bulk Density
Db vs. Ksat Db vs. Φm
0
0.2
0.4
0.6
0.8
1
1.2
0.000 0.100 0.200 0.300 0.400 0.500
porosity
den
sity
(g/m
l)
0
0.2
0.4
0.6
0.8
1
1.2
0 0.02 0.04 0.06 0.08 0.1 0.12
Ksat (cm/sec)
den
sity
(g
/ml)
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Discussion
• Correlation bet. Φm and Ksat : Kozency-Carman Eq. (Giménez et al. 1997, Comegna et al. 2000, Gloaguen et al. 2001, Jarvis et al. 2002 )
Ksat α Φmμ
y = - 0.2662x - 0.8734R2 = 0.6773
- 0.8
- 0.7
- 0.6
- 0.5
- 0.4
- 0.3
- 0.2
- 0.1
0
- 2 - 1.5 - 1 - 0.5
log(Ksat)
log(p
oro
sity
)
Correlation appears only in A
horizons
μ = -0.2662
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Discussion
• Correlation bet. slope and Φm
• Correlation bet. slope and Ksat only in A horizons (Lee et al. 1999)
Slope vs. Ksat (A)
0
0.02
0.04
0.06
0.08
0.1
0.12
0 5 10 15 20 25
slope (degree)
Ksa
t (c
m/s
ec)
Slope vs. Porosity (A)
y = 0.0057x + 0.2548R2 = 0.5368
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0 5 10 15 20 25
slope (degree)
Poro
sity
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Discussion
• Correlation bet. slope and Φm decay rate
• Correlation bet. slope and Ksat decay rate
Slope vs. Ksat decay rate
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25
slope (degrees)
Ksa
t dec
ay r
ate
(1/m
)
Slope vs. Porosity decay rate
0
0.1
0.2
0.3
0.4
0.5
0.6
0 5 10 15 20 25
slope (degrees)
po
rosi
ty d
ecay
rat
e (1
/m)
Further study needs
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Conclusions
• Some soil variables (e.g., Ksat, Φm, Ksat decay rate, Φm decay r
ate) may be estimated from topological indices (ex. slope).
• Topological index can be considered in patch partitioning
![Page 29: Field and laboratory experiments for parameterizing soil variables at complex tarrain Tae Hee Hwang, Seongwon Eum, and Dowon Lee Graduate School of Environmental.](https://reader036.fdocuments.net/reader036/viewer/2022062517/56649f0e5503460f94c231ee/html5/thumbnails/29.jpg)
References
Comegna, V., P. Damiani and A. Sommella. 2000. Scaling the saturated hydraulic conductivity of a vertic ustorthens soil under conventional and minimum tillage. Soil and tillage research 54: 1-9.Gimenez, D., E. Perfect, W.J. Rawls, Ya. Pachepsky. 1997. Fractal models for predicting
soil hydraulic properties: a review. Engineering geology 48: 161-183.Gloaguen, F. , M. Chouteau, D. Marcotte, and R. Chapuis. 2001. Estimation of hydraulic conductivity of an unconfined aquifer using cokriging of GPR and hydrostratigraphic data. Journal of applied geophysics 47: 135-152.Jarvis, N.J., L. Zavattaro, K. Rajkai, W. D. Reynolds, P. -A. Olsen, M. McGechan, M. Mecke, B. Mohanty, P. B. Leeds-Harrison, and D. Jacques. 2002. Indirect estimation of near-saturated hydraulic conductivity from readily available soil information. Geoderma 108: 1-17.