Impact of precipitation variability on the performance of a rainfall-€“runoff model in Mediterranean mountain catchments

Losses in performance of a low-dimensional rainfall–runoff model resulting from changes in the annual precipitation are assessed for five catchments located in a mountainous Mediterranean environment, the Troodos Mountains, Cyprus. For an increase of 25% or a decrease of 15% in the cumulative precipitation depth of a five-year period, model performance losses become significant: the model robustness criterion reaches 13% and simulated cumulative runoff is under- or overestimated by up to 20%. However, only the 25% decrease in the precipitation depth influences the ability of the model to predict runoff dynamics (10% decrease in the Nash-Sutcliffe coefficient). This indicates the occurrence of either non-stationary effects or temporary secondary hydrological processes, which tend to amplify the decrease (or increase) in runoff production during the drier (or wetter) period. In addition, losses in model performance are analysed between one catchment and another. High performance losses despite close physical catchment properties show the poor transferability of model parameters in this environment.