New Satellite Tracks Earth's Rivers Over Year, Finds Less Dramatic Swings

NASA-French SWOT mission provides first-of-its-kind data on river height and width changes globally.

Published on Mar. 5, 2026

Got story updates? Submit your updates here. ›

A new study using data from the NASA-French SWOT satellite has found that the world's rivers experienced significantly less dramatic seasonal swings in water volume than previous model-based estimates. The satellite's precise measurements of river height and width over the course of a year revealed an aggregate change of 313 cubic kilometers, about 28% less than the lowest previous estimates. The findings also provided new insights into the underwater topography of river channels around the world.

Why it matters

The SWOT mission is the first satellite capable of surveying nearly all the world's lakes and rivers with high precision, providing a revolutionary new dataset to understand the global water cycle. Previous estimates of river volume changes relied on models or indirect measurements, so SWOT's direct observations are helping scientists untangle longstanding uncertainties about how much water flows through river systems over time.

The details

The study analyzed nearly 1.6 million observations from SWOT between October 2023 and September 2024, tracking 127,000 river segments. It found the Amazon River experienced the most dramatic annual changes, gaining and losing 172 cubic kilometers - enough to cover the state of California in over a foot of water. In contrast, the Nile River varied much less than expected, only changing by 8.5 cubic kilometers, likely due to upstream damming and drought. The new data also revealed previously unmapped details about the underwater topography of river channels around the world.

  • SWOT was launched in December 2022 from Vandenberg Space Force Base in California.
  • The study analyzed SWOT data collected between October 2023 and September 2024.

The players

SWOT

The Surface Water and Ocean Topography (SWOT) satellite is a collaboration between NASA and the French space agency CNES. It is the first satellite capable of surveying nearly all the world's lakes and rivers with high precision.

Cedric David

The lead of the SWOT research team that conducted the study at NASA's Jet Propulsion Laboratory.

Arnaud Cerbelaud

A postdoctoral research fellow at JPL who co-led the study on SWOT's river observations.

Got photos? Submit your photos here. ›

What they’re saying

“We're starting to untangle some of the really tough questions SWOT was built for. This is just the beginning.”

— Cedric David, Lead of the SWOT research team at NASA's Jet Propulsion Laboratory (Mirage News)

“The implications go far beyond hydrology and will help us understand how water moves through the global Earth system.”

— Arnaud Cerbelaud, Postdoctoral research fellow at JPL (Mirage News)

What’s next

Researchers say the SWOT mission is still in its early stages, and they expect to gain even more insights into global river systems as the satellite continues collecting data over the coming years.

The takeaway

The SWOT satellite's unprecedented measurements of river height and width changes have provided the first direct observations of how much water flows through the world's rivers over time, challenging previous model-based estimates and revealing new details about the underlying topography of river channels globally.