Evaluating the transferability of monthly water balance models under changing climate conditions

Monthly water balance models (MWBMs) are often used for making flow projections under climate change. As such, these models should provide accurate flow simulations; however, they are seldom evaluated in this regard. This paper presents a comprehensive framework intended for the evaluation of the applicability of MWBMs under changing climatic conditions. The framework consists of analyses of consistency in model performance, parameter estimates and simulated water balance components, and a subjective assessment of model transferability. Four MWBMs – abcd, Budyko, GR2M and WASMOD – are used to simulate runoff in the Wimmera catchment affected by the Millennium drought. Although abcd and Budyko slightly outperformed GR2M and WASMOD, none of the models performed well in transfer to the driest period. The greatest variability is detected in simulated groundwater storage and baseflow; thus, these model components should be improved and/or enhanced calibration strategies should be employed to advance the transferability of MWBMs under changing climate.