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LERAT ET AL.: VALUE OF UPSTREAM FLOW MEASUREMENTS X - 11where ˆQ T OT AL is the calculated discharge at the TOTAL catchment outlet, RR is therainfall-runoff operator, ROUT is the routing operator, θ is a unique parameter set applied180to the RR model on the two areas UP and INT, and ρ is the parameter set of the routingoperator.For the benchmark model, we constrained the parameters of the RR models to beidentical on the UP and INT areas to avoid compensations between the two RR models.Systematic tests (not presented here) were conducted with higher degrees of freedom in185the parameterization of RR models, but we found that the configuration with identicaltel-00392240, version 1 - 5 Jun 2009190195parameters for the two subcatchments was the one providing the best simulations on bothUP and TOTAL gaging stations.Note that upstream flows that are calculated by this model constitute truely blind simulations,without any calibration against observed data at the UP station (see section 3.4). section 3With similar notations, the UP-Meas model calculates downstream discharges as:ˆQ T OT AL = RR (θ ′ , P INT , P E INT ) + ROUT (ρ ′ , Q UP ) (2)Compared to equation 1, the model uses upstream measured discharges Q UP instead of equationvalues calculated by an upstream model ( ˆQ UP ). In this case, calibrated parameters arelimited to the RR parameters θ ′ on the intermediate area INT and the ROUT parametersρ ′ . Using measured upstream flow data, this model excludes the upstream subcatchmentfrom the modeling scheme.D R A F T July 24, 2008, 3:43pm D R A F T