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With the onset of warmer global temperatures, an increase in precipitation is predicted for low-latitude regions of northern Australia, while the southern parts are predicted to become drier. Water is a critical resource, yet little is currently known about the actual amount of groundwater available, let alone how the resource is changing. The Gravity Recovery and Climate Experiment (GRACE) satellite mission began in 2002 and has a proven capacity to measure variations related to hydrological patterns. GRACE can generate estimates of mass variations which can be interpreted as the sum of ground water, soil moisture, surface and atmospheric water. Such information can provide data on water resources at the basin-scale, information that is not readily available at the present time.

To date, the capability of the GRACE mission has not been utilised to study the temporal variations in water resources in Australia. Before the results of the analysis of GRACE data can be used, the accuracy of the estimates must be quantified. How much "error" is introduced into the estimates of Australian drainage basins from the leakage of signal from real mass variations elsewhere in the world? What is the smallest drainage basin area that can be investigated in the Australian region, while still achieving estimates of sufficient accuracy to provide useful information? Which of the four international centres generating montly GRACE solutions is the most accurate for the Australian region?

A regional approach has significantly higher resolution than a spherical harmonic approach for detecting the crustal deformation after the 2004 Sumatra earthquake; therefore, it is likely to permit drainage basins of smaller area to be assessed separately. We intend to develop software to generate regional GRACE solutions for studying the Australian drainage basins.