  Increasing aridification of continental areas due to global climate change
has impacted freshwater availability, particularly in extremely dry landmasses,
such as Australia. Multiple demands on water resources require integrated basin
management approaches, necessitating knowledge of total water storage, and
changes in water mass. Such monitoring is not practical at continental scales
using traditional methods. Satellite gravity has proven successful at
documenting changes in total water mass at regional scales, and here we use
data from the Grace and Grace-FO missions, spanning 2002 - 2020, to track
regional water budget trends in Australia most heavily utilised basin systems,
including the Murray-Darling Basin. The period of analysis covers the
Millennium drought (2002-2009) and 2010-11 heavy flooding events, which
contribute significant signal variability. However our extended datasets
demonstrate a negative trend in the geoid anomaly over the Murray-Darling Basin
of -1.5mm, equivalent to a water loss rate of -0.91 Gt yr-1. With the exception
of northern Australia, similar scale geoid declines are observed in most
Australian basin systems analysed - implying declining total water storage.
Long-term declines in water availability require concerted management plans,
balancing the requirements of agriculture and industry, with domestic use,
traditional owners, and healthy freshwater ecosystems.
