Quels apports hydrologiques pour les modèles hydrauliques? Vers ...

X - 4LERAT ET AL.: VALUE OF UPSTREAM FLOW MEASUREMENTS1. Introduction1.1. Back to good old principlesExisting hydrological models, either distributed or lumped, aim at calculating river flowat a catchment outlet using rainfall and potential evapotranspiration as inputs. Often,when the catchment studied is large or when it is densely monitored, gaging stationsexist upstream of the target outlet. What benefit can be expected from this additional35information in hydrological modeling? although all hydrologists agree that upstream flowtel-00392240, version 1 - 5 Jun 2009404550observations can provide valuable information for downstream flow modeling, there isno consensus on how this additional information should be integrated in the modelingprocess, nor the advantages and limits it can have.Several authors [e.g., Corradini, 1991, Michaud et al., 1994, Feyen et al., 2008] reportsignificant improvements in downstream simulations when upstream discharges areaccounted for in the modeling scheme.However, streamflow measurements do not correspond to classical hydrological modelsinputs, simply because hydrologists are used to regarding streamflows as a model output[Sivapalan et al., 2003]. Moreover, the use of measured upstream flows introducesadditional constraints by limiting simulations to periods where these data are available,meaning that the model cannot be applied to assess future flow conditions.Last, the quality of stream flow measurements can also raise problems, especially whenthe upstream station’s rating curve is uncertain [Clarke, 1999, Petersen-Øverleir, 2004].If upstream flow measurements are to be used as an additional input to hydrologicalmodels, their impact on model performance should be quantified, and the potential forD R A F T July 24, 2008, 3:43pm D R A F T