À12.9 and À52.6% for irrigation, drinking water and industrial processes, respectively (Table 1). Current groundwater total uptake is 996 Mm
3 a
À1 , divided into
73%, 17% and 10% for drinking water, industrial processes and irrigation, respectively. Regarding the 1900s simulation, the assumption is made that most of the
withdrawals were taken from surface water in the early twentieth century. For this
simulation, there are no groundwater withdrawals.
5.3 Climate Scenarios
5.3.1 Reanalysis of the Past
The 1900s scenario climate variables are described using newly materialised reconstructions over long-term atmospheric reanalysis elaborated by Bonnet [21]. The
reanalysis is based upon the twentieth-century NOAA 20CRv2c reanalysis [18],
which was downscaled [20] following a statistical downscaling strategy [103, 104]
that mobilises the ISBA-MODCOU chain [38, 105]. These data, downscaled at the
SAFRAN grid scale, integrate the use of homogenised observations in the process of
statistical downscaling in order to ensure a correct reproduction of the spatiotemporal variability of precipitation, temperature and river flows.
5.3.2 Selecting an Appropriate Climate Product for the Projection
Many worldwide climatic reanalysis and prediction products exist. Owing to differences in model structure, parametrisation and regionalisation, these products generate
dissimilar results for precipitation and potential evapotranspiration, which eventually
lead to distinct hydrological predictions [104, 106–108]. More precisely, while
hydrological parametrisation and regionalisation are of the utmost importance for
the evaluation of hydrological functioning at the seasonal scale, climate modellers
agree on the fact that climate models are the dominant source of uncertainty in future
climate projection [106–108]. To evaluate the impact of climate change on regional
hydrosystems, various approaches are used [109], mostly based on statistical downscaling [6, 104, 109] or the use of a regional climate model such as in the EUROCORDEX initiative [110]. To analyse the Seine hydrosystem trajectory in the future,
we therefore decided to pay careful attention to the ability of the method to reproduce
the current state of the system, as recommended by Radanovics et al. [111]. Projection
data from four GCMs and one regional climate model from the Fifth Coupled Model
Intercomparison Project (CMIP5) [5] were therefore disaggregated at the scale of
SAFRAN grid and made available for the 1850–2100 period. Data from the following
models were analysed: CanESM2 (Canada), MIROC5 (Japan), BCC-CSM-1-1-m
(China), CSIRO-Mk3-6-0 (Australia) and Aladin-Climat (France).
As shown in Sect. 1.2, the hydrology of the Seine is responsive to long periods of
climatic fluctuations due to large-scale climatic phenomena, such as the NAO.
74
N. Flipo et al.
3 a
À1 , divided into
73%, 17% and 10% for drinking water, industrial processes and irrigation, respectively. Regarding the 1900s simulation, the assumption is made that most of the
withdrawals were taken from surface water in the early twentieth century. For this
simulation, there are no groundwater withdrawals.
5.3 Climate Scenarios
5.3.1 Reanalysis of the Past
The 1900s scenario climate variables are described using newly materialised reconstructions over long-term atmospheric reanalysis elaborated by Bonnet [21]. The
reanalysis is based upon the twentieth-century NOAA 20CRv2c reanalysis [18],
which was downscaled [20] following a statistical downscaling strategy [103, 104]
that mobilises the ISBA-MODCOU chain [38, 105]. These data, downscaled at the
SAFRAN grid scale, integrate the use of homogenised observations in the process of
statistical downscaling in order to ensure a correct reproduction of the spatiotemporal variability of precipitation, temperature and river flows.
5.3.2 Selecting an Appropriate Climate Product for the Projection
Many worldwide climatic reanalysis and prediction products exist. Owing to differences in model structure, parametrisation and regionalisation, these products generate
dissimilar results for precipitation and potential evapotranspiration, which eventually
lead to distinct hydrological predictions [104, 106–108]. More precisely, while
hydrological parametrisation and regionalisation are of the utmost importance for
the evaluation of hydrological functioning at the seasonal scale, climate modellers
agree on the fact that climate models are the dominant source of uncertainty in future
climate projection [106–108]. To evaluate the impact of climate change on regional
hydrosystems, various approaches are used [109], mostly based on statistical downscaling [6, 104, 109] or the use of a regional climate model such as in the EUROCORDEX initiative [110]. To analyse the Seine hydrosystem trajectory in the future,
we therefore decided to pay careful attention to the ability of the method to reproduce
the current state of the system, as recommended by Radanovics et al. [111]. Projection
data from four GCMs and one regional climate model from the Fifth Coupled Model
Intercomparison Project (CMIP5) [5] were therefore disaggregated at the scale of
SAFRAN grid and made available for the 1850–2100 period. Data from the following
models were analysed: CanESM2 (Canada), MIROC5 (Japan), BCC-CSM-1-1-m
(China), CSIRO-Mk3-6-0 (Australia) and Aladin-Climat (France).
As shown in Sect. 1.2, the hydrology of the Seine is responsive to long periods of
climatic fluctuations due to large-scale climatic phenomena, such as the NAO.
74
N. Flipo et al.