2019 SWCS International Annual Conference July 28-31, 2019 Pittsburgh, Pennsylvania

1. Modeling stream runoff from three
watersheds with different forest stands in
Korea using the WEPP model
Hakjun Rhee, Hung Tae Choi, and Anurag Srivastava

2. 2
1. Background and Objectives
Water Resources Management by Managing Forests
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA
Nation/
Region
Species/
forest type
Treatment Change in runoff
USA Whole US LAI 20%, 50%, 80% decrease 3%, 8%, 13% increase
CA 40% thinning 9% increase
AZ Ponderosa 50% thinning 8% increase
Japan Japanese
cypress
58% thinning (43% DBH area)
241mm (7.4% individual, 4.8% monthly
precipitation increase)
Australia Eucalyptus
12~50% thinning
10~35% increase
(effect lasts for 4~15 years)
Italy Calabrian
pine
50% thinning (30% DBH area)
Groundwater increase in spring
and summer
Greece Oak 50% DBH area 13.2 mm increase
Turkey Deciduous 11% thinning 8 mm increase in first year
Oak 18% thinning No change in RO (20% threshold)
W Africa Minimum 50% thinning Runoff increase

3. 3
 Forest watershed can be managed for water resources, and watershed
modeling is needed to access the effects of forest management
(thinning, timber harvesting, and wildland fire) on water resources
 Forest watershed modeling in Korea
1) Choosing a physically-based model and modeling for baseline
conditions (long-term undisturbed forest)
2) Modeling for managed (disturbed) forest conditions
1. Background and Objectives
Forest Watershed Modeling in Korea
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

4. 4
 WEPP (Water Erosion Prediction Project)
− A physically-based and distributed-parameter watershed hydrology and
erosion model
− WEPP simulates the hydrologic and erosion impacts of
i. Climate
ii. Soil
iii. Topography
iv. Land use and vegetation growth
− WEPP outputs daily water balance, sediment yield and deposition
− Adequate for small-size watersheds
2. Method
WEPP Model
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

5. 5
 Various types of interfaces
2. Method
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

6. 6
2. Method
Modeling Sites in Korea
o Gwangneung-Conifer
o Watershed size: 13.6 ha
o Annual precip: 1,503mm
o Soil depth: 30~60cm
o Parent rock: Granite gneiss
o Soil texture: Sandy Loam
o Forest type: Conifer
o Species: Korean pine, fir
o Age class: IV
o Gwangneung-Deciduous
o Watershed size: 22.0 ha
o Annual precip: 1,503mm
o Soil depth: 30~60cm
o Parent rock: Granite gneiss
o Yangju-Mixed
o Watershed size: 5.2 ha
o Annual precip: 1,503mm
o Soil depth: 30~60cm
o Parent rock: Granite gneiss
o Soil texture: Sandy loam
o Forest type: Deciduous
o Species: Oak, Japanese larch
o Age class: VI
o Soil texture: Sandy loam
o Forest type: Mixed
o Species: Pine, oak
o Age class: IV
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

7. 7
2. Method
WEPP Inputs and Information
for Modeling Sites in Korea
 ArcGIS version 10.3.1
 Inputs
− Climate: Korea Meteorological Administration AWS (Automatic Weather System)
data for Gwangneung and Yangju
− Soil: Modified sandy loam forest soil file based on western US
− Topography: 5m DEM (ASCII) from NIFoS (National Institute of Forest Science)
of Korea Forest Service
− Land use: Forest file (Forest.rot) in WEPP and LAI (Leaf Area Index) 6
− Muskingum Cunge method for water balance
 At least 15 years of monitoring stream runoff data (2003-2017)
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

8. 8
 GIS WEPP modeling for Gwangneung-Conifer
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

9. 9
3. Results
WEPP Stream Runoff Modeling
 Gwangneung-Conifer daily precipitation, observed runoff, and WEPP
simulated runoff from 2003 to 2007
0
20
40
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180
2000
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

10.  Gwangneung-Conifer daily precipitation, observed runoff, and WEPP
simulated runoff from 2008 to 2012
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0
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160
180
2000
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

11.  Gwangneung-Conifer daily precipitation, observed runoff, and WEPP
simulated runoff from 2013 to 2017
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0
20
40
60
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140
160
180
2000
10
20
30
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

12.  Gwangneung-Conifer monthly precipitation, observed runoff, and
WEPP simulated runoff
12
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

13. 13
 Results comparisons for Gwangneung-Conifer
Average annual precipitation: 1,394 mm
Observed annual runoff: 797 mm
Observed ET rate: 42.8%
WEPP simulated annual runoff: 555 mm
WEPP simulated ET rate: 60.8%
NSE (Nash-Sutcliffe Efficiency): 0.723
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

14.  GIS WEPP modeling for Gwangneung-Deciduous
14
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

15.  Gwangneung-Deciduous daily precipitation, observed runoff, and
WEPP simulated runoff from 2003 to 2007
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0
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140
160
180
2000
10
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30
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50
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90
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

16.  Gwangneung-Deciduous daily precipitation, observed runoff, and
WEPP simulated runoff from 2008 to 2012
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0
20
40
60
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140
160
180
2000
10
20
30
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90
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

17.  Gwangneung-Deciduous daily precipitation, observed runoff, and
WEPP simulated runoff from 2013 to 2017
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0
20
40
60
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160
180
2000
10
20
30
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50
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

18.  Gwangneung-Deciduous monthly precipitation, observed runoff, and
WEPP simulated runoff
18
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

19. 19
 Results comparisons for Gwangneung-Deciduous
Average annual precipitation: 1,394 mm
Observed annual runoff: 1,011 mm
Observed ET rate: 27.5%
WEPP simulated annual runoff: 566 mm
WEPP simulated ET rate: 59.4%
NSE (Nash-Sutcliffe Efficiency): 0.668
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

20.  GIS WEPP modeling for Yangju-Mixed
20
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

21.  GIS WEPP modeling for Yangju-Mixed
21
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

22.  Yangju-Mixed daily precipitation, observed runoff, and WEPP simulated
runoff from 2003 to 2007
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0
20
40
60
80
100
120
140
160
180
2000
10
20
30
40
50
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90
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

23.  Yangju-Mixed daily precipitation, observed runoff, and WEPP simulated
runoff from 2008 to 2012
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0
20
40
60
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120
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160
180
2000
10
20
30
40
50
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

24.  Yangju-Mixed daily precipitation, observed runoff, and WEPP simulated
runoff from 2013 to 2017
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0
20
40
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160
180
2000
10
20
30
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Precip(mm)
Runoff(mm)
Month-Year
prcp Obs RO WEPP RO
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

25.  Yangju-Mixed monthly precipitation, observed runoff, and WEPP
simulated runoff
25
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

26. 26
 Results comparisons for Yangju-Mixed
Average annual precipitation: 1,350 mm
Observed annual runoff: 724 mm
Observed ET rate: 46.4%
WEPP simulated annual runoff: 496 mm
WEPP simulated ET rate: 63.3%
NSE (Nash-Sutcliffe Efficiency): 0.570
3. Results
WEPP Stream Runoff Modeling
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

27. 27
4. Conclusions
 NSEs shows that WEPP simulates stream runoff reasonably (NSE = 0.723,
0.668, 570)
 WEPP underestimated stream runoff, especially in winter and spring
 Observed ET rates of 42.8%, 27.5%, 46.4%, as compared to WEPP simulated
ET rates of 60.8%, 59.4%, 63.3% for Gwangneung-Conifer, Gwangneung-
Deciduous, and Yangju-Mixed
− ET in Korea forests < ET in western US
 Currently only conifer forest type
− Increases a difference in deciduous forest type
 Parameterization and enhancement needed on WEPP soil and land use
inputs (e.g., deciduous and mixed forest types, LAI) to simulate different
forest conditions in Korea
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA

28. 28
Thank you
Modeling stream runoff from three watersheds with different forest stands in Korea using the WEPP model
Rhee H, Choi HT, Srivastava A7/31/2019 @ Pittsburgh, PA