Post on 04-Jan-2016
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
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
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
Study Area
Gwangneung Experimental Forest, Gyonggi-do, Korea
Seoul
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
Sampling points
Field measurements
• Soil type
• Effective soil depth
• Soil color
• Slope
• Vegetation type
• Aspect
• Bedrock
Soil type, soil depth, soil color
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)
Saturated hydraulic conductivity (Ksat)
time
Macroporosity (Φm)(pF 2.7)
pF meter DIK-3340
Daiki Co. Ltd.
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
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
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
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
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
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
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)
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)
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)
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)
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
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
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
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
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.