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criterion by 0.04 at Siloam Springs when adding the third tributary (Figure 6)and the 5% drop in EP at Tahlequah when adding the second tributary. Moresurprisingly, the best performance is not always obtained with the highest levelof inflow resolution: the best NSE and E P in validation mode at Tahlequah500comes with the second tributary. It appears that, with the point inflow option,introducing additional tributaries that are modelled individually may degradethe quality of simulations.5.2.2 Influence of the choice of tributariestel-00392240, version 1 - 5 Jun 2009505510The previous results raise the question of tributary ordering: as indicated inSection 4, tributaries are ordered by catchment area to first introduce largecontributions and then refine by adding smaller ones. The results mentionedpreviously reveal that this strategy might not be optimal, at least for option2. To check this point, we compared this strategy with all possible combinationsof a fixed number of tributaries selected among the six identified onFigure 1. The performance criteria were then calculated for each combinationand compared with the value obtained with the initial catchment orderingstrategy.515Figure 10 shows the mean NSE values over the two sub-periods obtained invalidation mode obtained after calibrating the coupled model with all possiblecombinations of three tributaries. Similar figures would be obtained withanother number of tributaries.This figure helps us address the difficult question of choosing the right set oftributaries. The results of the two injection options are classified by decreasingNSE values. Rank 1 gives the best option for the coupled model. In addition,24