Estimating Salt Loads in High Water Table Areas. II: Regional Salt Loads

This paper describes the development of MIDASS, a lumped conceptual model for the prediction of streamflow and salt yield from irrigated catchments with high water tables. The model is suited for application to medium-sized catchments, though several models can be linked into a cascade arrangement for the simulation of catchments several hundred square kilometers in area. The model requires daily values of rainfall and irrigation deliveries as well as potential evaporation. As streamflow routing is not undertaken, model output is suited to weekly or monthly estimates of yield. The model was calibrated on a gauged 465 km2 subcatchment of the Tragowel Plains Irrigation Area in south eastern Australia. Considering differences in scale, the relative proportions of baseflow, exfiltration, and runoff were found to agree reasonably well with physically based model results from a 9 ha study site. The model was applied to the Tragowel Plains to test the impacts of a number of irrigation and drainage management options on downstream river salinity.