An experimental flood on the Colorado River in Arizona yielded only mixed success in restoring habitat below a dam. KPCC's Molly Peterson says the research could inform Western river restoration in California.
For more than a dozen years, U.S. Geological Survey scientists have been testing how to divert sand from Lake Powell back into the Colorado River below the Glen Canyon Dam.
Sand feeds beaches, survey officials say. Flies that fish eat increase — and invasive species decrease — in rebuilt habitat. The geological survey's Theodore Melis says scientists first thought to flood water when sand from smaller rivers builds up enough in the Colorado River, "like perhaps savings in a bank account. We found that wasn't really occurring mostly because the sand grains coming in from the tributaries are so small and fine. So the idea changed to try and strike while the iron is hot," he says.
In a third round of study, two years ago, sending water quickly down the river returned more sediment to where it used to lie. The new sandbars didn't last; they've swept away. Melis says the study shows that rebuilding habitat can work — more than once. He says "the real question now is can it be maintained at some desired level over the long term."
The federal government will use the study to manage the Colorado River in Arizona — and to inform restoration projects throughout the West.