Assessment of the Performance of a Distributed Code in Relation to the ET<Subscript>p</Subscript> Estimates

This article is a preliminary report of a research activityfocusing on the effects of the crop potentialevapotranspiration (ET<Subscript>p</Subscript>) generation methods on boththe performance of a distributed catchment model as well ason the magnitude of its main effective parameters. Thereferred effects were assessed on the basis of theindependent Multi-Calibration (MC) of the distributed modelfor which three different ET<Subscript>p</Subscript> scenarios were generatedas 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. ET<Subscript>p</Subscript> was estimated as a function of the reference crop evapotranspiration (ET<Subscript>o</Subscript>) by means of the k <Subscript>c</Subscript>-ET<Subscript>o</Subscript> approach. For assessing the performance of theestimation approach, the ET<Subscript>o</Subscript> outputs of the three scenarioswere compared to local ET<Subscript>o</Subscript> constraints derived from a previous research. The outputs of scenario B and scenario C showed a close agreement with the local ET<Subscript>o</Subscript> constraints. Their effect on the performance of the hydrological model alsoseemed to be comparable. The output of scenario A producedhigher estimates than the outputs of the other two scenarios, inthe order of 200 mm per year. The best model performance was obtained by using the estimates of scenario A. The research alsorevealed the weak dependency of the model effective parametersinspected in this preliminary research on the ET<Subscript>p</Subscript>estimating methods. Copyright Kluwer Academic Publishers 2002