Application of linear and nonlinear techniques in river flow forecasting in the Kilombero River basin, Tanzania

Modelling of the rainfall-runoff transformation process and routing of river flows in the Kilombero River basin and its five sub-catchments, within the Rufiji River basin in Tanzania was undertaken using three system (black-box) models-a simple linear model, a linear perturbation model and a linear varying gain factor model-in their linear transfer function forms. A lumped conceptual model-the soil moisture accounting and routing model-was also applied to the sub-catchments and the basin. The HEC-HMS model, which is a distributed model, was applied only to the entire Kilombero River basin. River discharge, rainfall and potential evaporation data were used as inputs to the appropriate models and it was observed that sometimes the system models performed better than complex hydrological models, especially in large catchments, illustrating the usefulness of using simple black-box models in data-scarce situations.