Groundwater Modeling Breakthrough

A University of Wyoming professor has made a discovery that answers a nearly 100-year-old question about water movement, with implications for agriculture, hydrology, climate science and other fields

After decades of effort, Fred Ogden, UW's Cline Chair of Engineering, Environment and Natural Resources in the Department of Civil and Architectural Engineering and Haub School of Environment and Natural Resources, and a team of collaborators published their findings in the journal Water Resources Research this spring. The paper, titled "A new general 1-D vadose zone flow solution method," presents an equation to replace a difficult and unreliable formula that's stymied hydrologic modelers since 1931.

"I honestly never thought I would be involved in a discovery in my field," Ogden says.

He anticipates this finding will greatly improve the reliability and functionality for hundreds of important water models used by everyone from irrigators and city planners to climate scientists and botanists around the country and the world, as well as trigger a new surge in data collection.

In 1931, Lorenzo Richards developed a beautiful, if numerically complex, equation to calculate how much water makes it into soil over time as rainfall hits the ground surface and filters down toward the water table. That equation, known as the Richards equation and often shortened to RE, has been the only rigorous way to calculate the movement of water in the vadose zone—that is, the unsaturated soil between the water table and the ground surface where most plant roots grow.

Calculating the movement of water in the vadose zone is critical to everything from estimating return flows and aquifer recharge to better managing irrigation and predicting floods. But RE is extremely difficult to solve, and occasionally unsolvable. So, while some high-powered computer models can handle it over small geographic areas, simpler models or those covering large regions must use approximations that compromise accuracy.

For decades, hydrologists and other scientists have pursued a better way to estimate vadose zone water. Cornell University Environment and Ecology Professor Jean-Yves Parlange and Australian soil physicist John Robert Philip battled one another in the literature, proposing new equations and disproving each other—from the 1950s until Philip's untimely death in a traffic accident in 1999. Princeton Environmental Engineering and Water Resources Director Michael Celia published a partial solution in 1990 that is not reliable in all circumstances.

Source: Phys.org

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