In 1983, scientists poured dye into Wyoming’s Popo Agie River before it vanished underground; two hours later, it resurfaced about 3,500 feet away with more water than entered

In Sinks Canyon State Park in west-central Wyoming, the Middle Popo Agie River does something few rivers do: it disappears underground. At a point known as the Sinks, the river's entire flow vanishes into a cave system instead of continuing along an open channel.

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