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X - 10LERAT ET AL.: VALUE OF UPSTREAM FLOW MEASUREMENTS3.1. Three versions of the model using upstream flow data differentlyThe model splits the TOTAL catchment into an upstream subcatchment UP and an160intermediate area INT, as presented in Figure 1. It consists of (1) a lumped rainfall-runoff Figure 1operator to generate runoff from mean areal rainfall and potential evapotranspiration (PE)on the two nested catchments (see section 3.2) and (2) a routing operator to propagate section 3upstream flows toward the catchment outlet (see section 3.3). Three versions of the model section 3are tested (see Figure 2), as indicated in the introduction: Figure 21651. A benchmark model is calibrated and run in validation mode without using upstreamtel-00392240, version 1 - 5 Jun 2009170175flow measurements (neither in the calibration nor in the validation mode).2. The UP-Meas model is calibrated and run in validation mode using upstream flowmeasurements. This model is used to investigate the conditions under which upstream flowmeasurement can significantly influence downstream simulations and to test the sensitivityof downstream simulations to the quality of upstream flow data.3. The UP-Sim model is calibrated using measured upstream flow but run in validationmode with upstream flows simulated by an upstream submodel. This model is used tocheck the performance changes when upstream flow measurements must be replaced withcalculated values.In the benchmark model, downstream flows are calculated from mean areal rainfall andPE on the UP subcatchment (P UP and P E UP respectiveley) and INT intermediate area(P INT and P E INT respectively) as follows:ˆQ T OT AL= RR (θ, P INT , P E INT ) + ROUT(ρ, ˆQ)UP(1)ˆQ UP = RR (θ, P UP , P E UP )D R A F T July 24, 2008, 3:43pm D R A F T