The Murray Darling Depression Bioregion occurs across the southwest corner of NSW and extends into Vic and SA. It is a shallow depression that filled with marine and terrestrial sediments over the last 50-60 million years. Most of the bioregion contains sandy soils that originally supported Mallee woodland and heathland vegetation. Native grassland occurs on grey cracking clays on the Wimmera Plains in Victoria and as isolated patches of Iron-grass Tussock Grassland in South Australia.
Hot semi-arid climate in the northern section of the bioregion and a warm semi-arid climate in the southern half of the bioregion. Mean annual rainfall is low - between 210 and 408 mm. Annual rainfall on the Wimmera Plains is 350-500 mm
Iron-grass Natural Temperate Grasslands of South Australia; Natural grasslands of the Murray Valley Plains (Wimmera plains); Seasonal Herbaceous Wetlands (Freshwater) of the Temperate Lowland Plains