Pacific Swell

Southern California environment news and trends

UCLA scientists find shortcut to estimating a river's volume

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80460 full

People around the world depend on rivers for their water supply.   So it’s important to understand how much water a river holds.  Researchers at UCLA have found a new way to calculate a river’s volume without ever stepping into it.

When the Ganges River floods, engineers in India know how to respond because they measure how wide the river is, how deep it is, and how fast it’s moving. But India doesn’t share that information with Bangladesh, downstream – so the swollen river hits that country harder.

“Many other countries consider river flow data to be state secrets,” said UCLA’s Laurence Smith.

He and his student, Colin Gleason, have figured out a way to make river discharge more transparent. Now, even where it’s not possible to take direct measurements of a river, hydrologists can make a very good estimate of a river’s volume using pictures collected from space.

“The availability of satellite images for this purpose and for other purposes has exploded in the last 20 years,” he said.

Smith says Gleason used “brute force” – a lot of computer time, lines and lines and lines of code – to study long-used equations for calculating a river’s volume. They’re rooted in geometry, length, times width, times depth, but are far more complicated.

“What Colin and I found is that there’s a redundancy hidden inside these classic equations that nobody discovered in sixty years,” Smith said.

In other words, he and Gleason found a shortcut through that math.

Using those images, and a lot of computer time, Smith and Gleason confirmed their technique by comparing data and observations about several rivers, including the mighty Mississippi. Smith says this new tool can help people better understand how much water is in the world’s rivers – regardless of where a country’s borders fall.

The study is published today in the Proceedings of the National Academy of Sciences.


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