iahs 2013, gothenburg a comparative assessment of awbm and simhyd for forested watersheds bofu yu 1,...
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IAHS 2013, Gothenburg
A comparative assessment of AWBM and SimHyd for forested watersheds
Bofu Yu1, Zhongli Zhu2
1School of Engineering, Griffith University, Australia2 School of Geography, Beijing Normal University, China
IAHS 2013, Gothenburg
Background• Workshop objective: to apply and evaluate model
performance in simulating ‘non-stationary’ hydrologic time series;
• Climate and streamflow data were provided for 14 watersheds/catchments around the world;
• Protocol was stipulated for consistency for all modellers;
• AWBM and SimHyd are by far the most commonly used models for streamflow estimation in Australia;
• Two smallest of the 14 watersheds/catchments were selected for comparison purposes.
IAHS 2013, Gothenburg
Two models
AWBM SimHyd
Model type Conceptual Conceptual
Developer Walter Boughton Francis Chiew
Where model developed Brisbane, Australia Melbourne, Australia
Latitude (degree) -27.50 -37.78
Time step Daily Daily
No. of parameters 8 9
Input data requirements Rainfall and potential evaporation
Rainfall and potential evaporation
IAHS 2013, Gothenburg
AWBM
IAHS 2013, Gothenburg
SimHyd
IAHS 2013, Gothenburg
Model comparison
0 20 40 60 80 1000
20
40
60
80
100
Run
off (
mm
)
Excess rain (mm)
AWBM SimHyd SCS-CN
With default parameter values for AWBM and SimHyd, and max. retention value of 105mmfor the SCS Curve Number method,all models show a non-linear relationship between rain excess and runoff.
NB: All the ‘stores’ in AWBM and SimHyd were assumed to be half full initially.
IAHS 2013, Gothenburg
Two watershedsRimbaud Fernow
Country France The U.S.
Watershed The Ruisseau du Rimbaud at Collobrieres
The Fernow EF River at Watershed 6
Closest major city Nice Pittsburgh
Latitude (degree) 44.24 39.07
Area (km2) 1.4 0.2
Period 1967-2006 1959-2009
Land use Forest Forest
Cause for non-stationarity
Fire in 1990 Clearing 1964-68, re-forestation in 1973
Gross runoff coefficient 60% 41%
Solid prec./total prec. <1% 14%
IAHS 2013, Gothenburg
- models developed - watersheds applied
IAHS 2013, Gothenburg
Working Hypotheses
• None of the 2 models is going to work;• Conceptual models would perform better for
watersheds with a higher runoff coefficient and (for these 2) with less snow fall
IAHS 2013, Gothenburg
Two watershedsRimbaud Fernow
Country France The U.S.
Watershed The Ruisseau du Rimbaud at Collobrieres
The Fernow EF River at Watershed 6
Closest major city Nice Pittsburgh
Latitude (degree) 44.24 39.07
Area (km2) 1.4 0.2
Period 1967-2006 1959-2009
Land use Forest Forest
Cause for non-stationarity
Fire in 1990 Clearing 1964-68, re-forestation in 1973
Gross runoff coefficient 60% 41%
Solid prec./total prec. <1% 14%
IAHS 2013, Gothenburg
Model comparisonin terms of the N-S coefficient of efficiency for 30
calibration-validation combinations
AWBM SimHydFernow, the US 0.43±0.11 0.40±0.12Rimbaud, France 0.79±0.07 0.77±0.09
There is a much larger difference between watersheds than between models!!
IAHS 2013, Gothenburg
Model performance in terms of NSE between 2 watersheds
0.0 0.2 0.4 0.6 0.8 1.00
1
2
3
4
5
6
7
8
9
10
No.
Ec
AWBM for Fernow
0.0 0.2 0.4 0.6 0.8 1.00
1
2
3
4
5
6
7
8
9
10
No.
Ec
AWBM for Rimbaud
Histograms of the Nash-Sutcliffecoefficient of efficiency for 30 calibration-validation combinations(level 1 & 2 requirements)
IAHS 2013, Gothenburg
Rimbaud
1965 1970 1975 1980 1985 1990 1995 2000 2005 20100
200
400
600
800
1000
1200
1400
1600
1800
2000F
low
(mm
)
Year
Qobs Qsim
Fire
IAHS 2013, Gothenburg
Rimbaud
1965 1970 1975 1980 1985 1990 1995 2000 2005 20100
20
40
60
80
100S
tand
ardi
sed
cum
ulat
ive
prec
and
flow
Year
cumP cumQ constant
IAHS 2013, Gothenburg
Fernow
1960 1970 1980 1990 2000 20100
200
400
600
800
1000
1200F
low
(m
m)
Year
Qobs Qsim
clearing and reforestation
IAHS 2013, Gothenburg
Fernow
1960 1970 1980 1990 2000 20100
10
20
30
40
50
60
70
80
90
100S
tand
ardi
sed
cum
ulat
ive
prec
and
flow
(%
)
Year
cumP cumQ constant
IAHS 2013, Gothenburg
Observed hydrologic changes at Fernow
Variable Period No. of years Rate(mm.yr-1)
p-value
Precipitation 1959-1986 28 +6.7±3.1 0.04
Streamflow 1959-1986 28 +11.4±2.5 <0.01
Precipitation 1986-2009 24 -2.2±5.5 0.69
Streamflow 1986-2009 24 -10.1±4.6 0.04
Precipitation 1959-2009 51 1.3±1.5 0.40
IAHS 2013, Gothenburg
Fernow
1960 1970 1980 1990 2000 20100
200
400
600
800
1000
1200F
low
(m
m)
Year
Qobs Qsim
clearing and reforestation
IAHS 2013, Gothenburg
Observed hydrologic changes at Rimbaud
Variable Period No. of years Rate (mm.yr-1)
p-value
Precipitation 1968-2006 39 -11.3±4.3 0.01
Streamflow 1968-2006 39 -14.8±4.2 <0.01
Both precipitation and streamflow havesignificantly decreased over the 39 year period.
IAHS 2013, Gothenburg
Rimbaud
1965 1970 1975 1980 1985 1990 1995 2000 2005 20100
200
400
600
800
1000
1200
1400
1600
1800
2000F
low
(mm
)
Year
Qobs Qsim
Fire
IAHS 2013, Gothenburg
Conclusions (what we have learnt from this exercise)
• Difference in model performance is small if calibration method is used consistently;
• Source of non-stationarity is important;• Conceptual models tested are adequate in describing
the effect of changes in precipitation, not the effect of changes in vegetation;
• Changes to streamflow are greater than those in precipitation for these watersheds.
IAHS 2013, Gothenburg
Conclusions ..(what we have learnt from this exercise)
• The effect of the fire in the Rimbaud watershed is secondary in the context of the overwhelming decreasing trend in precipitation and streamflow over the 39 years;
• The 2 conceptual models tested did not perform well for the Fernow (W6) watershed because of the significant increase in streamflow early in the study period, and the subsequent significant decrease in streamflow from 1986. And it snows a lot over there.
IAHS 2013, Gothenburg
Thank You!