Assistant fire chief Mike Cairns says the girl jumped into the icy water of Lynn Creek late Monday afternoon.
Cairns says she hurt her back and was treated for hypothermia as well as a possible neck injury.
He says the teen was able to make it to a rock at the centre of the river and stabilize herself until crews could reach her.
The girl was rescued from the area of Twin Falls, a spot Cairns says is not safe because pools are shallower than usual.
Officials have not released the teen's name or age. (News 1130)
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