Prediction limits of a catchment hydrological model using different estimates of ETp

Abstract

A joint deterministic–stochastic protocol based on Monte Carlo simulations (MCS) was applied to themodelling of a medium size catchment using two significantly different sets of potential evapotranspira-tion (ETp) data, estimated through a Penman-based method. Modelling error was accounted using theGeneralised Likelihood Uncertainty Estimation (GLUE) methodology. Both, water routing and water bal-ance related parameters were considered in the analysis. The research revealed that the hypothesis of theless correct ETpdata set being appropriate for the current modelling could not be rejected since modelparameters adjusted to compensate for the use of significantly different ETpdata sets. The GLUE analysisdemonstrated that the model predictions exhibited some sensitivity to the hydraulic conductivity of oneof the geological layers. Furthermore, the study revealed a considerable error attached to the simulationof both high and low flows, as well as, piezometric levels, for every ETpdata set, which was most likelymagnified by the coarse time and spatial scales used in the current modelling.