The Surface Water and Ocean Topography (SWOT) mission is set to revolutionize global hydrological research by improving measurements of river basins worldwide.

Using data from the SWOT satellite, launched in December 2022, scientists aim to calculate the amount of water flowing in rivers by looking at factors like the height, width, and slope of the water surface. This river discharge data, reflecting the volume of water transported through a river cross-section, is expected to be available about a year after the satellite launch and will focus on rivers wider than 100 meters.

An international team of researchers, including Earth Sciences Professor and Byrd Center Principal Investigator Michael Durand and Postdoctoral scholar Steve Coss from The Ohio State University, collaborated on a study published in the American Geophysical Union's (AGU's) Water Resources Research journal earlier this year. This study outlines how SWOT discharge is derived, discusses its expected accuracy, and breaks down sources of uncertainty into random and systematic components. The study suggests that the uncertainty in discharge measurements will likely be below 30% for most river segments globally. The Byrd research team and others will validate this accuracy prediction.

Investigators expect that SWOT will measure changes in river discharge fairly accurately (within 15% for most rivers). However, the discharge values may have a constant offset or bias compared with the true discharge, which could be approximately 25%. A separate SWOT data product that uses in situ gages to remove bias will be created and will have less bias in areas where gages are available. 

SWOT's precise measurements of streamflow changes mean it can provide accurate data about how water flow varies during events in river basins worldwide. Although this data is mainly available for larger rivers and sampled approximately every ten days, it still represents a valuable new resource for understanding global hydrological processes. Overall, the study emphasizes the SWOT mission's transformative potential in reshaping the hydrological science field.

Read more about this study by visiting AGU's Water Resources Research.