Dryland salinity is on the increase in the upper catchments of the central and northern river valleys of New South Wales (Murray Darling Basin Ministerial Council- MDBC, 1999). Tile consequence of this is increased salinity in river water. This could adversely affect irrigated schemes downstream: as irrigation with moderate to highly saline water can lead to increased salinity in the root-zone, if there is insufficient leaching. In order to determine the potential impact and long-term sustainability of irrigated production we need to know the spatial distribution of soil and effects of water quality changes. Important also is the soil-water balance, which needs to be modelled in order to provide estimates of potential salinity accumulation and deep drainage as affected by the current quality of irrigation water. Worst-case scenarios can be applicable in this case.