Integration of a Kalman filter in the HBV hydrological model for runoff forecasting

A standard Kalman filter was developed with the purpose of updating certain state variables of the lower zone function and the output of the HBV model. The global version of the HBV model, functioning with an hourly time step, was calibrated by trial and error to the Tunisian basins of the Barbara and Mellila Wadis. The daily time step was considered for evaluating the quality of the data reconstitution. The model was then coupled with the Kalman filter by reformulating the conceptual model as a system. of dynamic state equations and implementing the Kalman filter procedure. The hourly discharge hydrograph constitutes the introduced measurement to correct state variables. Despite a literature-driven selection of the errors on measurements and system states, this filter clearly allowed reduction of the uncertainty on discharge produced by the rainfall-runoff process and the precipitation input.