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A model for the world's rivers?

The Liwu River in Taiwan. The steep mountain rivers of Taiwan not only cut down rapidly through rock, they also migrate laterally, changing the map pattern of the river networks.
[Image courtesy of Sean Willett]

A new model can predict how river networks evolve over time, and it might help researchers understand what some landscapes looked like in the past—or how they will look in the future. And since rivers act as both pathways and barriers for many creatures, this new model might tell researchers more about the ways that rivers affect natural ecosystems.

Sean Willett and colleagues studied how river basins and drainage divides (also called watersheds) shift over time in response to water cutting through the land and the upward movement of tectonic plates beneath our feet.

The researchers used their new model on three major river systems around the world—in China, Taiwan and the United States—and they found that features of those river networks, including channels, basins and watersheds, generally move around until they reach a state of equilibrium. Then, the landscape stops shifting, according to Willett and his team.

Based on the model's results, the researchers say that the Yellow River in China has stopped evolving and is now stationary. But, the younger rivers of Taiwan—and the older rivers of the southeastern United States—are still slowly moving around and adjusting, they say.