Black Canyon below Hoover dam is popular for canoeing. I don't think there are any rapids.
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www.americanwhitewater.org]
The Virgin river has several sections of whitewater, especially in the Virgin narrows. Check the AW river pages for Utah, Nevada and Arizona.
[
www.americanwhitewater.org]
I think Las Vegas releases treated waste water into the Virgin on down into Lake Mead. Might be worth checking out.
It is fairly easy to get permits to float the Colorado River from Diamond Creek down into Lake Mead. You can find contact info on the AW Grand Canyon page.
With Lake Mead so low, there are rapids on the Colorado river in Iceberg Canyon, a few miles upstream of South Cove. Supposedly there is a good surf wave there.
I imagine the flat water paddling on Lake Mead could be pretty interesting.
There might be other paddling options available that locals know about.
Paul