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Titel |
Climate and hydrological uncertainties in projections of flood and low-flows in France |
VerfasserIn |
E. Sauquet, J.-P. Vidal, C. Perrin, P.-Y. Bourgin, M. Chauveau, S. Chazot |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250063324
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Zusammenfassung |
Changes in river flows are associated with different types of uncertainties, due to an imperfect
knowledge of both future climate and rainfall-runoff processes. Due to computational
constraints, impact and adaptation studies unfortunately cannot always afford to perform a
detailed analysis of all these uncertainties. In that case, the modelling efforts have to focus on
the most relevant source of uncertainty in order to provide the best estimate of the overall
uncertainty.
As part of the national Explore2070 project, the present study thus aims at assessing the
hierarchy of uncertainties in changes on river flow extremes at the scale of France. Amongst
all possible sources of uncertainties, two are here considered: (1) the uncertainty in General
Circulation Model (GCM) configuration, with 7 different models that adequately sample the
range of changes as projected by the GCMs used in the IPCC AR4 over France, and
(2) the uncertainty in hydrological model structure, with 2 quite different models:
GR4J (Perrin et al., 2003), a lumped conceptual model, and Isba-Modcou (Habets
et al., 2008), a suite of a land surface scheme and a distributed hydrogeological
model.
The hydrological models have been run at more than 1500 locations in France over the
1961-1990 baseline period with forcings from both the Safran near-surface atmospheric
reanalysis (Vidal et al., 2010) and the GCM control runs downscaled with a weather type
method (Boé et al., 2006), and over the 2046-2065 period with forcings from all downscaled
GCM runs under the A1B emissions scenario. Various high flow indices (annual maximum
daily flow with return period of 10 and 20 years, the daily flow value exceeded 10% of the
time) and low flow indices (annual minimum monthly flow with a 5-year return period,
annual minimum 10-day mean flow with a 2-year return period, the daily flow value
exceeded 95% of the time) as well as seasonality indices have been computed for both
periods.
An analysis of variance has been performed for each river flow index and at all stations
shared by the two hydrological models (around 500) in order to assess the two considered
sources of uncertainties in index changes as well as their hierarchy. Results first show spatial
differences in the amount of sampled uncertainties due to both sub-regional climate
specificities and catchment properties. The analysis of hierarchy between climate and
hydrological uncertainties show striking differences (1) over France for a single index and (2)
between different indices. The part of uncertainty relative to the hydrological response for
example appears to be much more important for low-flow indices than for high-flow
indices.
Experiments have additionally been performed to possibly reduce the overall
uncertainty by weighting combinations of GCM and hydrological model through
their ability of reproducing observed river flow extreme values over the baseline
period.
The results of this study will help to define the relevant hydrological scenarios to be used
in the adaptation part of the Explore2070 project for deriving national-scale adaptation
strategies.
Boé et al. (2006) A simple statistical-dynamical downscaling scheme based on
weather types and conditional resampling. Journal of Geophysical Research,
111, D23106. doi: 10.1029/2005JD006889
Habets et al. (2008) The SAFRAN-ISBA-MODCOU hydrometeorological model
applied over France. Journal of Geophysical Research, 113, D06113. doi:
10.1029/2007JDOO8548
Perrin et al. (2003) Improvment of a parsimonious model for streamflow simulation.
Journal of Hydrology, 279, 275-289. doi: 10.1016/S0022-1694(03)00225-7
Vidal et al. (2010) Multilevel and multiscale drought reanalysis over France with the
Safran-Isba-Modcou hydrometeorological suite. Hydrology and Earth System
Sciences, 14, 459-478.doi: 10.5194/hess-14-459-2010 |
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