A One-Parameter Groundwater Discharge Model Linked to the IHACRES Rainfall-Runoff Model

A simple groundwater discharge model that uses a modest number of parameters (1-3) has been developed. The model uses three parameters (transmissivity (T), effective porosity (g) and hillslope length (L)) to model groundwater level as a function of position along the hillslope, and discharge to the stream. If discharge alone is required (groundwater level is not modelled), then the model requires only one parameter. The model has been linked with the IHACRES rainfall-runoff model, with recharge being estimated within the IHACRES model. The discharge formulation within the groundwater model is expressed as a series of exponential terms, and is therefore similar to the commonly used form of the unit hydrograph approach, implemented in streamflow models such as IHACRES. The model is being tested on a variety of catchments in the Lachlan and Macquarie Basins, located in the Murray-Darling Basin in NSW, Australia. The catchments range from 1.6 km2 to 2000km2. This allows for the catchments to be represented by single, or multiple hillslopes. Details of the revised groundwater model are presented, as well as modifications made to the IHACRES rainfall-runoff model. Future developments of the model are also discussed.