Assessing the accuracy of SWOT measurements of water bodies in Australia

The Surface Water and Ocean Topography (SWOT) mission provides an unparalleled observation system for monitoring global surface water resources. For the Australian continent, where many rivers and wetland systems are unmonitored, SWOT data offers a new and unrivalled observation dataset, yielding constraints and knowledge for water management systems. Here, we assess which of the many SWOT data sets are able to provide information in the Australian setting and we quantify the accuracy of the estiates against a series of in situ gauge measurements. The SWOT water heights derived from the raster product are found to have a weighted root-mean-square error of ~5 cm but the product fails to sample small water bodies such as narrow rivers<$40 m wide. We found that, with careful filtering of the pixel cloud data, comparable levels of accuracy can be obtained, including on rivers ~40 m wide and reservoirs as small as ~$100x100 m.