ESTIMATING SALT LOADS IN HIGH WATER-TABLE AREAS .2. REGIONAL SALT LOADS

This paper describes the development of MIDASS, a lumped conceptual mo del for the prediction of streamflow and salt yield from irrigated cat chments with high water tables. The model is suited for application to medium-sized catchments, though several models can be linked into a c ascade arrangement for the simulation of catchments several hundred sq uare kilometers in area. The model requires daily values of rainfall a nd irrigation deliveries as well as potential evaporation. As streamfl ow routing is not undertaken, model output is suited to weekly or mont hly estimates of yield. The model was calibrated on a gauged 465 km(2) subcatchment of the Tragowel Plains Irrigation Area in south eastern Australia. Considering differences in scale, die relative proportions of baseflow, exfiltration, and runoff were found to agree reasonably w ell with physically based model results from a 9 ha study site. The mo del was applied to the Tragowel Plains to test the impacts of a number of irrigation and drainage management options on downstream river sal inity.