Incorporating groundwater recharge and discharge functions into an existing monthly rainfall-runoff model

There is an urgent need for an integrated Surface water and groundwater modelling tool that is suitable for southern African conditions and can be applied at various basin scales for broad strategic water resource planning purposes. The paper describes two new components (recharge and groundwater discharge) that have been added to an existing monthly time-step rainfall-runoff model that is widely used in the southern African Subcontinent. The new components are relatively simple, consistent with the existing model formulation, but based oil accepted groundwater flow principles and Well understood groundwater parameters. The application of the revised model on two basins in southern Africa with quite different baseflow characteristics has demonstrated that the new components have a great deal of potential, even if the improvement is only to be able to simulate the groundwater baseflow component of total runoff more explicitly. More comprehensive testing and comparison of the results with existing groundwater and geohydrological data is required, while some extensions to the new components need to be considered to ensure that the model call be considered applicable to a wide range of basin and climate types.