The data set used in the validation of SWAGSIM was adopted inthe current study. River stage data, spatially variable irrigation scheduling data andclimatic data was reviewed and altered where necessary; the groundwater parameterisation was accepted without modification. All available hydrograph data was collated to define an objective function that was used by the model to optimise the infiltration and recharge exponents assigned to each of the three spatially assigned soil classes. The model optimiser seeks to minimise the error between the simulated groundwater heads and the observed hydrograph data basedon the algorithm developed by Nelder and Mead (1965).

The calibrated model simulated the groundwater trends within acceptable limits of accuracy. Figures 4 and 5 show the simulated depth to watertable for selected cells relative to the corresponding observation data. Also shown is the applied irrigation, rainfall and simulated soil moisture contents. The maximum hydrograph rms calculated for the 17 observation bores was 0.36 m; the simulated soil moisture contents were supported by field observations.

Simulated salt export from the catchment broadly reflects measured data.
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Figure 4: Simulated and observed hydrograph for bore 221; also shown is the corresponding soil moisture content, the daily rainfall (mm) and applied irrigation (mm).