Share icon
Jessica Sheaves, NASA Earth Applied Sciences writer
First AEM
Rosemary Knight in front of the helicopter used for Stanford’s first AEM survey. Credits: Ryan Smith

In 2014, Rosemary Knight had access to a helicopter and an ambitious idea. She wanted to use the geophysical imaging equipment mounted beneath the helicopter to see below the Earth’s surface, specifically to see where groundwater aquifers were rapidly dwindling in California’s San Joaquin Valley.

Knight is a professor of geophysics at Stanford University, with a dedication to “knowledge into action,” Knight’s personal motto. Together with Ryan Smith, one of her PhD students at the time, and collaborators at Aqua Geo Frameworks (who generously offered to provide access to the helicopter and imaging equipment) and the Tulare Irrigation District, she collected an invaluable geophysical data set. They used electrical resistivity (a measurement of how strongly an object — in this case water-filled sediments under the Earth’s surface — resists an electric current) to map the groundwater basin beneath the Tulare Irrigation District. This type of data collection is called an Airborne Electromagnetic (AEM) survey.

Foothills AEM
AEM system flying over the Pine Flat Dam. Credits: Kings River Conservation District

The survey was so successful that the method has become a core part of groundwater management in California. The state recently finished making a $13 million investment in geophysical imaging and has gathered 27,000 kilometers (about 17,000 miles) of groundwater basin data.

“I've been working on using various geophysical methods to image groundwater systems for about 30 years now,” Knight said. “And suddenly people really care. Suddenly when there is a shortage, when groundwater is in the news … people have come to realize that it's very challenging to understand what's going on in the groundwater systems without using some form of remote imaging.”

The remarkable data set acquired by the state presented yet another opportunity. Knight teamed up with Meredith Goebel, a research scientist working with her at Stanford, to explore how to combine the imaging data with satellite data to update a groundwater model. They went back again to Aaron Fukuda in the Tulare Irrigation District with a new idea: What if we were able to help you monitor the pumping of groundwater and better model what is happening? This would provide a new approach to managing the groundwater in the district. And as before, Knight was quick to say, having a local partner was critical to the success of the project.

Rosemary Knight and Meredith Goebel
Rosemary Knight and Meredith Goebel. Credits: Stacy Geiken

A Water Savings Account

Groundwater is like a water savings account, Goebel explained. It’s there to access in times of need. But most people would never withdraw money without knowing how much was in their account or without replenishing it.

"You need to be tracking those resources in order to make sure that you're not going to hit your overdraft fee,” Goebel said. “And a lot of times people just don't have enough data or enough tools to adequately track that. We work on building those methods, those tools, so that you have the information you need to make the management decisions.”

Subsidence is one of the signs of hitting a water “overdraft fee,” but there’s more to sinking land than water usage. The makeup of the basin layers plays a role in how much subsidence can occur. For example, layers that are rich in clay tend to deform and sink more than sand-rich layers.

The original groundwater model didn’t account for subsidence, a property which was added to the updated model. She and Knight gathered an additional 800 kilometers (just under 500 miles) of AEM data and used these data to inform the model layers, adding a new layer to the model that separated out the clay-rich areas.

“That was really important because when we add the subsidence modeling to the model, we assign properties to the entire layers,” Goebel said. “The next thing we did was to map out clay content everywhere in the model. When we do the subsidence modeling, we have to input key information such as ‘this layer has this percentage of clay’, as that's going to be where deformation occurs.’”

Goebel and Knight’s approach allowed them to use the model to predict both water levels and subsidence. They recently presented the updated model to the water agencies they’ve been partnering with. Those agencies have begun adding Knight and Goebel’s model to their management workflows. The model will allow them to understand how different management scenarios could impact the future availability of groundwater and subsidence. This information will be crucial in their efforts to prioritize areas with the highest risk factors and meet California’s groundwater management milestones.

A Commitment to Knowledge into Action

There were many factors that made Goebel and Knight’s work so successful. Both geophysicists named partnerships with water agencies as a key factor. They also acknowledged that their close working relationship was another. Their ability to amplify and support each other’s strengths helped take this project to new heights.

Part of the reason they work so well together is that, while decades apart in entering the field of geophysics, their backgrounds and experiences share many similarities. Both Knight and Goebel grew up with a strong love of math and physics. Knight’s father was a physicist and Goebel’s an engineer. Both women were driven to pursue their field by watching their fathers’ examples. But they wanted to do more than pursue knowledge for its own sake. They wanted to apply their knowledge to real-world problems. This drive for “knowledge into action” eventually led them both to near-surface geophysics.

Things clicked for Goebel during a summer program run by the Society of Exploration Geophysicists (SEG). There, she was exposed to a range of different ways people applied geophysics to different problems. At school, professors and peers mostly talked about applications in the oil industry, earthquakes, and deep Earth imaging. But seeing environmental applications opened up a whole new world.

“I realized I can do the science that I enjoy and think is fun, and I can apply it to problems that I found meaningful,” Goebel explained. “And that’s how I found Rosemary [Knight]. She was one of the key people who was actually doing this — and with real-world partners.”

They’ve been working together ever since. Goebel stayed on as a research scientist at Stanford after earning her PhD. The dynamic duo complements each other well. While Knight is the “big ideas” person, Goebel helps her iron out the practical details.

“My advisor, Amos Nur, greatly valued ideas and creativity — he was very encouraging of all I did,” Knight said. “He once posted on his office door: ‘Details are the worms that eat away at great ideas.’ And I have to say this resonated with me. My husband will say ‘But how are you going to do this?’ and I’ll respond ‘Details, details! Trust me, this will work.’ My husband often describes me as fearless.”

Knight credits Goebel for ensuring that her big ideas come together. In addition to her modeling work, Goebel plays an important role in working with their partners. She handles communications and collects and analyzes the information partners provide. “I get to do the fun things that Rosemary puts in motion,” Goebel explained. “I keep the ball rolling.”

Knight said that the richer the interaction a university has with its outside partners, the more rewarding the research is. And having someone dedicated to supporting the coordination with those partners acts as a multiplier factor on projects.

“I can do more than I would ever imagine, probably more than I should ever imagine, because there's Meredith [Goebel] who can help with many of the partnerships that come into play the moment you turn knowledge into action,” Knight said. “If every university professor everywhere in the world could have a Meredith, what is being done at universities would have a much greater impact on what's happening in the world.”

Creating Successful Partnerships

Rosemary Knight with Aaron Fukuda
Stanford Geophysics professor Rosemary Knight with Aaron Fukuda, manager of Tulare Irrigation District and key local partner on many geophysical projects. Credits: Meredith Goebel

Knight and Goebel acknowledged that taking a partnership-focused approach to research is more time intensive than the traditional research-to-publication track. But they feel the effort is worth it. For example, that partnership in the Tulare Irrigation District helped bring a local perspective to their data. When Aaron Fukuda, the district’s general manager, saw the maps of the area, he was able to help with the interpretation by pointing out someone’s well field and explaining what was happening there.

“They have so much local expertise and knowledge that lets us look at the data we're working with in a different way,” Goebel said. “Or they provide us data we didn't know existed which transforms what we're able to accomplish.”

"If we weren't able to just call them up and have them look at something or ask if they had data available, we wouldn't be able to get to where we are today.”

Part of what made this partnership work so well was the mindset the two scientists approached it with. Rather than being a one-way relationship, they were engaged from day one. Knight and Goebel thought about their partner’s needs, challenges, and experiences — and designed their project around them.

“People really matter to me — working with others is what I really enjoy,” Knight said. “And I believe it’s this and my commitment to knowledge into action that has allowed me to be successful, in the way in which I define success.”

Knight believes part of her outlook on working with others is due to being a woman in STEM (science, technology, engineering, and mathematics). Goebel feels the same. While she acknowledged it’s impossible to make a blanket statement about all male peers, she felt that females tend to be socialized differently and approach problems differently. She’s credited those differences as being instrumental in her work.

“I genuinely value the partnerships and relationships we build,” Goebel said. “And the response you get from somebody when they know that you're genuinely interested in [what they’re doing], that it matters to you — they give you the same thing back.”

Blazing the Trail

Knight’s work on advancing the use of geophysics for groundwater science and management earned her one of the highest distinctions in geophysics. In 2021, she received the Maurice Ewing Medal from the Society of Exploration Geophysicists for her contributions to the field of groundwater geophysics. She was the first woman in the award’s 42-year history to receive it, and the first geophysicist focused on groundwater.

A colleague from the University of Texas reached out to let her know he intended to nominate her. Knight was hesitant at first. But he insisted. “He said, ‘Young people need to see this. If young people aren’t seeing people like you winning these top awards, what message are we sending?”

After she won, Knight received an outpouring of support from young women. “One person wrote and said they were in tears, partly out of joy,” Knight said. “But partly reflecting on the fact that in 42 years I was the first woman. It is sad. 2021, the first woman? You have to ask: how could it take this long?”

In early September, Knight was told that she had been made a Fellow of the American Geophysical Union and received the Ambassador award for “outstanding contributions in geophysics for water resource evaluation and pioneering efforts to build the community of near-surface geophysics.” Knight was quick to say that this award goes to her students, postdocs, research staff, and other collaborators who made it all happen – and made it all fun.

When asked what advice they’d give to young women considering a career in geophysics, both Knight and Goebel gave an enthusiastic “go for it!” Goebel said that although choosing a career feels like a big, permanent decision, it doesn’t have to be. Many of the skills she uses as a research scientist — coding, research, communications, project management — can easily transfer to nearly any other kind of work.

“Focus on what gives you joy,” Knight added. “Stick to your own definition of success. … The message from my parents always was: you’re not making forever decisions. Do what you love, and when you don’t love it anymore, stop doing it.”

After 23 years at Stanford, she still loves her job and the work she gets to do with Goebel, the rest of her team, and her network of partners.

Related Impact

Megan Gannon
Megan Gannon