NASA SWOT satellite

A New View of Earth’s Waters

NASA’s Surface Water and Ocean Topography (SWOT) mission, in which UMass Amherst researchers play a range of important roles, will reveal unprecedented observations about water and climate on a global scale.

Colin Gleason never ceases to be amazed by how much we don't know about water on Earth given how essential it is to every aspect of human society.

“Human beings have co-evolved with freshwater resources since human beings existed. Water is everything for people—food, energy, drinking water, industry,” said Gleason, a geographer, geoscientist, global hydrologist, and engineer in UMass Amherst’s Department of Civil and Environmental Engineering in the College of Engineering. “I get overwhelmed by the amount of stuff we don’t know and should know."

Colin Gleason
Colin Gleason, UMass Amherst associate professor of civil and environmental engineering.

That is poised to change thanks to a NASA mission in which UMass Amherst researchers—including faculty, staff, students, and alumni—play a range of integral roles. On December 15, 2022, NASA launched a satellite mission known as Surface Water and Ocean Topography (SWOT) that will revolutionize understanding of global hydrology. (The illustration at the top of the story shows the SWOT spacecraft with its antenna mast and solar arrays fully deployed. Credit: NASA/JPL-Caltech). Delwyn Moller ’97PhD and Daniel Esteban-Fernandez ’04PhD are radar engineers who have worked on SWOT, and Dragana Perkovic-Martin ‘08PhD led testing and aircraft integration of the airborne SWOT instrument. Meanwhile, the entire project is overseen by NASA Earth Science Division Director Karen St. Germain ’93PhD.



Gleason, who has worked on the SWOT project for more than a decade since he was a PhD student at UCLA, was at the satellite launch and described the energy as “total awe, in the truest sense.”
Watching the rocket slowly accelerate upward in the sky followed a giant fireball was so “loud and visceral.” After the satellite separated, Gleason described feeling multiple sonic booms in his chest as the rocket landed back on Earth. It was over in what felt like about 30 seconds, and a short time later, the satellite “booped” mission control to indicate a successful launch. Watch NASA’s live feed of the SWOT mission launch.

As exciting as launch day was, what comes next is even more thrilling. That’s because SWOT will, for the first time, provide real-time direct measurements of height, width, and slope for water on Earth. This includes oceans, virtually every river on the planet wider than 50 meters (over 200,000 in all), and six million lakes.

Making this global data universally available has major implications for human water management and the international politics of water, particularly in regions that are contentious and where information on water resources is currently kept hidden as a state secret. It will also give scientists new visibility into the effects of climate change.

“We’re really going after big first-order questions about the function of the planet,” Gleason said. “Better understanding water at these global scales helps us better understand our entire climate system.”

Early Days

The SWOT mission’s origins date back about two decades, and UMass Amherst researchers have been involved from the earliest days. As a PhD student at the University of Washington, Kostas Andreadis was an author on a foundational paper, published in the journal Geophysical Research Letters in 2006, which proved it was possible to estimate river discharge, or flow, from measurements that the mission could provide.

“For hydrologists, river discharge is the most important variable,” explained Andreadis, who today is assistant professor in civil and environmental engineering at UMass Amherst. “Once we proved discharge could be inferred, that really started everything. Since then, so many wonderful researchers have published fantastic work and built an entire ecosystem of knowledge that has made this mission possible.”

Andreadis’s work on SWOT took him next to Ohio State for a post-doc, then on to NASA’s Jet Propulsion Laboratory (JPL), where he was recruited to work on the mission. He joined the faculty at UMass Amherst in 2018, where he has continued contributing to SWOT alongside his other hydrology research.

Andreadis was a primary developer of one of SWOT’s discharge algorithms. With the mission launched, he will advise on any revisions needed.

He also looks forward to incorporating the data from SWOT into his own research in the Computational Hydrology Research Group, which uses computational tools to understand how human activity affects the water cycle, including floods and droughts. SWOT will provide a two-dimensional picture of water flow in rivers, lakes, and wetlands over a large swath of the globe—a valuable complement to the existing network of point measurements taken by hydrologists.

“SWOT’s observations are just truly unprecedented in hydrology,” said Andreadis. “I feel it could be really transformative for our field.”

Validation and Calibration

Taylor Rowley taking measurements on the Connecticut River.
UMass research fellow Taylor Rowley taking measurements on the Connecticut River as part of the validation and calibration efforts for the SWOT mission.

Following SWOT’s launch, the next step is to confirm—by taking measurements down on Earth—the accuracy of its data, and calibrate its instruments as needed. As lead academic scientist of validation for U.S. Inland Waters, Gleason is overseeing field work in diverse environments around the globe—from New Zealand to the Arctic to Alaska to Massachusetts' own Connecticut River. Because hydrologists didn’t have good ways to measure both the elevation and size (known as the “extent”) of lakes and rivers, he has spent about five years helping develop creative methods to do so over large areas. A team of French scientists is working on similar validation efforts in parallel, while yet another team is validating SWOT’s data on oceans.

We’re really going after big first-order questions about the function of the planet. Better understanding water at these global scales helps us better understand our entire climate system.

Colin Gleason, associate professor in Civil and Environmental Engineering

UMass research fellow Taylor Rowley is the lead technician for the inland waters field work. In spring and summer 2023, she is leading teams of researchers, including many UMass students, in taking measurements from a motorboat on the Connecticut River, in three separate sections stretching from Sunderland, Mass. to Middletown, Conn.

“This experience has been challenging in an exciting way,” she said. After years of preparation, the researchers have found that doing this work in the real world differs from the ideal scenarios they imagined in many ways, requiring them to make tricky in-field judgement calls. “The surprises have come in the form of how cold it can be on the water at speed, even if the air temperature is warm; how finicky boat motors can be; how much time certain tasks actually take, access to boat ramps, and river conditions,” she said.

While working on the Connecticut River, Rowley also has learned a great deal from interacting with locals who have spent their lives near the river. “They have so much knowledge to share and really want to understand what we are doing and why,” she said. “Communicating to the community like that has easily been my favorite part by far.”

Making Hydrology Data Globally Available

Gleason expects data from the SWOT mission to become publicly available beginning around September 2023. And there will be a lot of data.

“SWOT is a revolution on two fronts,” he explained. “As a piece of radar technology, it’s groundbreaking. It also yields an enormous quantity of data—about 20 terabytes every single day.” This volume of data is simply not practical to download, and will force scientists to work with the raw data in the cloud.

UMass Amherst student Elisa Friedmann taking measurements on the Connecticut River.
UMass Amherst PhD student Elisa Friedmann is part of a team of students from UMass and other institutions that are contributing to the SWOT validation and calibration efforts.

At this point, Gleason will put on yet another hat with the SWOT mission: co-lead of discharge production. His lab will run software, developed by almost 30 global scientists, to convert raw data on water height and extent into information on river discharge—the actual flux of water. The theory behind this process was first proposed by Gleason—and other scientists, independently—in 2014. The information produced by Gleason’s lab will be made publicly available in NASA’s SWOT River Database (SWORD). Hydrologists anywhere in the world can use it to look up discharge information for specific bodies of water.

“If it works, the world’s hydrology community will be using a UMass-made product for their research,” Gleason remarked, noting it builds on two decades of work by a massive global network of researchers.

He stressed that this approach involves an unusual level of cooperation between scientists around the world.

“For independent academic scientists to agree to work together in this way—to function like a mission with an overarching goal—I think is quite unique,” he said. “We’ve worked very hard at being a functioning political body over the past decade, and that has borne fruit. I think that the ultimate scientific products we generate are going to be better for it.”

This story was originally published in June 2023.