Large areas of Australia’s outback are currently used for unirrigated, low density beef cattle pasture :
Source:
Behrendt, 2016
If you irrigate land, there is potentially much more that you can do with it. However, a recent major CSIRO study of three regions in Northern Australia believed to have the strongest potential for water resource development found that:
This is because there are not many places where dams or other water storages are feasible from an engineering and water availability perspective, and even with water development, large areas are unsuitable for agriculture in terms of soils, climate, or other factors.
You can read more about the study and about the potential that does exist for water and agricultural development in Northern Australia here:
NAWRA Overview and findings.