Originally posted by Byrd Polar and Climate Research Center.

In the world of hydrologic science, a new chapter is being written with the advent of the Surface Water and Ocean Topography (SWOT) mission. This groundbreaking initiative, born from the collaboration of U.S. and French space agencies, is set to change how we understand and measure the world's river systems. The SWOT mission brings an innovative approach to gathering crucial data from both well-monitored and remote, unmonitored river basins across the globe.

Ohio State University's School of Earth Sciences Professor and Byrd Center Principal Investigator Michael Durand and his research group have coordinated the SWOT Discharge Algorithm Working Group for over ten years and are leading the effort to map river water flow from SWOT measurements.

Durand was part of an international collaboration and the lead author of the study "A Framework for Estimating Global River Discharge From the Surface Water and Ocean Topography Satellite Mission," published in Water Resources Research (WRR) last year. According to the American Geophysical Union, this research was one of the top five most-read WRR papers for 2023. 

The remarkable ability to measure the discharge of more than 100-meter-wide rivers is at the heart of this mission. By harnessing a range of parameters, including river surface elevation, width, and slope, along with other critical data, SWOT is poised to provide insights into the dynamics of river flows like never before.

A key focus of the mission is its precision in measuring river discharge. The approach is refined enough to distinguish between different types of errors in the measurements - random errors, known as standard errors, and systematic errors, or biases. The findings are promising; the discharge measurement uncertainty is expected to stay below 30% for approximately two-thirds of the world's river stretches, with systematic bias being the primary influencer.

An intriguing aspect of the mission is how it plans to integrate SWOT data with in-situ or on-site data. This combined method, referred to as 'gage-constrained' discharge estimates, aims to reduce the impact of systematic uncertainties further. Regarding the variations in river discharge over time, the mission's techniques are anticipated to capture these changes with a remarkable 15% accuracy for almost all river reaches. This level of detail is particularly vital for understanding the flow dynamics in rivers that lack traditional monitoring systems.

Overall, the SWOT mission is not just another step but a giant leap in hydrologic science. Its advanced methods in measuring discharge and unparalleled accuracy pave the way for new discoveries and understandings in the field, marking the beginning of an era of transformation in our comprehension of global river systems.

In December, NASA released the first public data products from the Ka-Band Radar Interferometer (KaRIn) on the SWOT satellite. Products with improved quality are planned for release soon. 

 You can read more about the study, one of the top five most-read WRR papers for 2023, or download it via PDF.