systematic testing of parameterizations to account for land cover changes in the gr4j model
DESCRIPTION
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 PresentationTRANSCRIPT
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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:
• 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