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Systematic testing of parameterizations to account for land cover changes in the GR4J model

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:

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Systematic testing of parameterizations to account for land cover changes in the GR4J model

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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

  2. 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)

  3. Forest hydrology experiments

  4. Courtesy of Sten Bergström, SMHI Dealing with changes within a conceptual model • Models are simplification of the physical reality

  5. 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

  6. Dealing with changes within GR4J

  7. 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)

  8. Questions asked • Is there a solution better than the others? • Can the variations of the recalibrated parameter be correlated to land use?

  9. Results (Fernow deforested catchment) average of the sub-periods calibration efficiency calibration efficiency for each sub-period

  10. Results (Fernow deforested catchment) conversion to conifers deforestation

  11. Results

  12. Results

  13. Results

  14. Results

  15. Parameter values evolution for the Fernow WS6 catchment

  16. Parameter correlation on urbanizing catchments (Blackberry)

  17. Parameter correlation on urbanizing catchments (Ferson)

  18. Conclusion A diagnostic which opens the way towards a parameterization of land-use changes remains (necessarily) model-specific

  19. Limits • More case studies are needed for more general results • Be careful with parameter interactions within the model

  20. Thank you

  21. Forest hydrology

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