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Systematic testing of parameterizations to account for land cover changes in the GR4J model. Vazken Andréassian Hydrosystems and Bioprocesses Research Unit, Irstea, Antony, France. Introduction. This presentation: - PowerPoint PPT Presentation
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1
Systematic testing of parameterizations
to account for land cover changes in the GR4J model
Vazken Andréassian
Hydrosystems and Bioprocesses Research Unit, Irstea, Antony, France
Introduction
This presentation:
• is based on data made available for the workshop (3 forested/deforested catchments + 2 urbanizing catchments)
• uses as example a single rainfall-runoff model (GR4J)
2
Forest hydrology experiments
Dealing with changes within a conceptual model
• Models are simplification of the physical reality
Cou
rtes
y of
Ste
n B
ergs
tröm
, SM
HI
Dealing with changes within a conceptual model
• Dealing with changing catchments is difficult with any model, but:
– within a physically-faithful model representation, the solution to account for the change is imposed
– within a conceptual model, the solution is not imposed, several possibilities exist
Dealing with changes within GR4J
Calibration strategy
• First calibrate a ‘central parameter set’ on the entire time series ( )
• Allow only one parameter to vary on each successive sub-periods (recalibration)
centralcentralcentralcentral4321 ,,,
Questions asked
• Is there a solution better than the others?
• Can the variations of the recalibrated parameter be correlated to land use?
Results (Fernow deforested catchment)
-100
-80
-60
-40
-20
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Calibration Period
Mod
el e
ffici
en
cy (
KG
E)
average of the sub-periods calibration efficiency
calibration efficiency for each sub-period
Results (Fernow deforested catchment)
-100
-80
-60
-40
-20
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Calibration Period
Mod
el e
ffici
en
cy (
KG
E)
conversion to conifers
deforestation
Results
-100
-80
-60
-40
-20
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Calibration Period
Mod
el e
ffici
en
cy (
KG
E)
ReferenceX1 recalibrated
Results
-100
-80
-60
-40
-20
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Calibration Period
Mod
el e
ffici
en
cy (
KG
E)
ReferenceX2 recalibrated
Results
-100
-80
-60
-40
-20
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Calibration Period
Mod
el e
ffici
en
cy (
KG
E)
ReferenceX3 calibrated
Results
-100
-80
-60
-40
-20
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Calibration Period
Mod
el e
ffici
en
cy (
KG
E)
ReferenceX4 recalibrated
Parameter values evolution for the Fernow WS6 catchment
Recalibrated parameter
Ref X1 X2 X3 X4
Deforested / reforested catchments
Fernow WS6 (cut & replanted with pines)
38.1 56.2 72.2 76.4 39.4
Rimbaud(forest fire)
74.1 85.3 86.2 82.2 80.3
Mörrumsån River at Lissbro(tree destruction by a storm)
80.2 85.8 87.7 90.0 81.6
Urbanized catchments
Ferson creek 65.5 79.4 83.6 80.0 70.6
Blackberry creek 70.4 79.3 80.5 76.5 72.0
Parameter correlation on urbanizing catchments (Blackberry)
Parameter correlation on urbanizing catchments (Ferson)
Conclusion
• A diagnostic which– opens the way towards a parameterization of land-
use changes
– remains (necessarily) model-specific
Limits
• More case studies are needed for more general results
• Be careful with parameter interactions within the model
Thank you
Forest hydrology
