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Assessment of the performance of a distributed code in relation to the ET<inf>p</inf> estimates

Abstract:

This article is a preliminary report of a research activity focusing on the effects of the crop potential evapotranspiration (ETp) generation methods on both the performance of a distributed catchment model as well as on the magnitude of its main effective parameters. The referred effects were assessed on the basis of the independent Multi-Calibration (MC) of the distributed model for which three different ETp scenarios were generated as follows: (A) FAO-24 standard approach; (B) FAO-24 approach but used with coefficients of the wind function and of the Stefan-Boltzmann equation selected according to local conditions; and (C) FAO-56 standard approach. ETp was estimated as a function of the reference crop evapotranspiration (ETo) by means of the kc-ETo approach. For assessing the performance of the estimation approach, the ETo outputs of the three scenarios were compared to local ETo constraints derived from a previous research. The outputs of scenario B and scenario C showed a close a agreement with the local ETo constraints. Their effect on the performance of the hydrological model also seemed to be comparable. The output of scenario A produced higher estimates than the outputs of the other two scenarios, in the order of 200 mm per year. The best model performance was obtained by using the estimates of scenario A. The research also revealed the weak dependency of the model effective parameters inspected in this preliminary research on the ETp estimating methods.