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LERAT ET AL.: VALUE OF UPSTREAM FLOW MEASUREMENTS X - 235.3. What happens when the model is run with calculated upstream flowinstead of measured values?The two previous sections have shown the critical value of upstream flow measurements415in a semidistributed model. Unfortunately, these data are not always available, especiallyduring the validation period where we want our models to be able to extrapolate withoutany flow measurements. In this section, we compare the results of the benchmark and theUP-Sim models.Table 3 shows that simulations improve significantly on the UP stations from benchmark Table 3420to UP-Sim but not on the downstream point TOTAL. It is striking that CEff statistics ontel-00392240, version 1 - 5 Jun 2009425430435the TOTAL station are nearly identical for both models. Indeed, one would have expectedsimulations on both points to benefit from the use of upstream flow measurements duringthe calibration process of UP-Sim.This counter-intuitive result, however, confirms some results which had been consideredrather paradoxical in the literature: Boyle et al. [2001] and Ajami et al., [2004] foundthat the distribution of the parameters over several subcatchments did not improve thesimulations compared to a simple uniform parameterization scheme (as in our benchmarkmodel). The fact that we used upstream flow measurements during the calibration process,which was not the case in the studies of Boyle et al.[2001] and Ajami et al.[2004], waseven a further advantage for the parameter-distributed strategy (UP-Sim model), but itdid not change the conclusion.Figure 9 provides insights into this result by comparing simulations of the benchmark Figure 9and the UP-Sim model on the example of the Vienne river (tributary of the Loire river inthe center of France). Figure 9 shows the simulations of the two models on the downstreampoint TOTAL and their breakdown into two components as per equations 1 and 3: theD R A F T July 24, 2008, 3:43pm D R A F T