[68]. All further results are therefore averaged over the 1993–2010 period to ensure
their significance [84].
The model uses daily rainfall and PET provided by SAFRAN [85, 86], a
mesoscale atmospheric analysis system for surface variables, producing data at a
daily time step on an 8 Â 8-km grid. SAFRAN uses the Météo-France observation
network and data from a number of well-instrumented stations. The anthropogenic
pressure on water resources is taken into account by means of water withdrawals in
each aquifer unit. The yearly amount of each uptake is provided by the SeineNormandie Water Agency.
4.1 General Two-Step Calibration Strategy of Hydrosystem
Models
Flipo et al. [68] proposed a stepwise calibration procedure for hydrosystem models.
This method is further developed here in the form of an innovative two-step
calibration methodology (Fig. 3) applied to the Seine basin [45]. The first step
consists in the calibration of surface parameters with a process-based multi-objective
function, which accounts for cumulative total river discharge and runoff dynamics.
The estimation of the runoff dynamics is based on a proper hydrograph separation.
Further details on the first step are given below. In the second step, subsurface
Fig. 3 Innovative two-step calibration procedure of the Seine basin with the CaWaQS model. The
outcome of each step is an optimal parameter set (bold case)
Pluri-annual Water Budget on the Seine Basin: Past, Current and Future Trends
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