| Summary: | Study region: Wami Ruvu basin (WRB; 66,899 km2) in Tanzania. Study focus: The objective of this study was to evaluate the performance, sensitivity, and uncertainty of the conceptual Hydrologiska Byråns Vattenbalansavdelning (HBV) model in WRB. The sensitivity, interdependency, and identifiability analysis was conducted to determine the most influential and uncertain parameters. The one factor at a time (OAT) method was used for evaluating parameter sensitivity whereas Monte Carlo Simulation (MCS) was employed for parameter identifiability analysis, model calibration, and quantifying prediction uncertainties. The model performance was evaluated by using statistical criteria, hydrographs, and Flow Duration Curves (FDCs). New hydrological insights for the region: The sensitivity analysis revealed that 7 parameters have a significant influence on model output. The degree of sensitivity was found to depend on objective functions and catchment characteristics. The identifiability analysis revealed significant parameter uncertainties which influence model predictions. However, most of the observed and simulated streamflow were within the 95 % uncertainty range. Also, the performance evaluation revealed that the observed streamflow were simulated with an acceptable degree of accuracy. Therefore, the model is suitable for WRB. These results will assist in efficient calibration, reducing uncertainties, and application of the HBV model, which is useful for planning and decision making in light of challenges associated with climate change, design, and management of water resources infrastructures in the region.
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