Harman compares his work on the movement of water to that of a demographer, who studies the age distribution—the mix of children, youth, and adults—in human populations. But, of course, raindrops can’t be counted like people.

“I’m trying to find useful mathematical computations for systems that are too complex for traditional physics to deal with,” he says. He’s had some success. He recently won a National Science Foundation CAREER Award for his research, and some of his work is currently being incorporated into the Chesapeake Bay Program’s latest computer model of the watershed. He also received the Early Career Award from the Hydrology Section of the American Geophysical Union, the world’s largest organization of geoscientists. But there is a lot more to do.

“We don’t really understand how the subsurface topography of the landscape evolves,” he says. “The structure of the ground beneath our feet bears the memory of the water that flows through it.”