Feasibility and uncertainty of using conceptual rainfall-runoff models in design flood estimation

Hydrological models are developed for different purposes including flood forecasting, design flood estimation, water resources assessment, and impact study of climate change and land use change, etc. In this study, applicability and uncertainty of two deterministic lumped models, the Xinanjiang (XAJ) model and the Hydrologiska Byrans Vattenbalansavdelning (HBV) model, in design flood estimation are evaluated in a data rich catchment in southern China. Uncertainties of the estimated design flood caused by model equifinality and calibration data period are then assessed using the generalized likelihood uncertainty estimation (GLUE) framework. The results show that: (1) the XAI model is likely to overestimate the design flood while HBV model underestimates the design flood; (2) the model parameter equifinality has significant impact on the design flood estimation results; (3) with the same length of calibration period, the results of design flood estimation are significantly influenced by which period of the data is used for model calibration; and (4) 15-20 years of calibration data are suggested to be necessary and sufficient for calibrating the two models in the study area.