of the Barwon River and the Bambra Fault to the south. This was done to enable a better representation of the regional groundwater system and to also incorporate possible (wider) causes to the salinity problem within the sub-catchment. Three soil types were spatially assigned across the domain; a single crop type was uniformly applied across the catchment. The groundwater system was conceptualised as a two layeraquifer system.

Figures 7 and 8 show the simulated and observed hydrographs for two bores, one in soil group 3 (high permeability) the other in soil group 1 (low permeability).

Figure 7: Simulated hydrographs for bore 4204 (soil group #3) derived using SMILES and Mike-SHE relative to observed data.

Figure 8: Simulated hydrographs for bore 4506 (soil group #1) derived using SMILES and Mike-SHE relative to observed data.

Conclusions

The simplified unsaturated model presented in this paper offers a fast and robust coupled saturated/unsaturated fully distributed solution scheme The degree of process description is commensurate with data availability. The model is shown to adequately describe groundwater response, soil moisture dynamics and salt export from both irrigated and dryland catchments. The conceptualisation of the unsaturated processes is a component of a decision support framework for exploring the impact of policy and programs on irrigation futures over a 20 year time period (Fordham and Malafant 1997).