Scientists Stir Things Up on River

Scientists said Wednesday that changes in the Colorado River were already apparent as a Grand Canyon flooding experiment began winding down.

The controlled flooding, aimed at restoring the canyon’s fragile ecosystem, began Sunday morning as the federal Bureau of Reclamation opened four giant steel tubes at Glen Canyon Dam, sending a torrent of water into the river. The experiment was to end early today.

Though scientists say the findings are still preliminary, changes to the river were visible.

Bennett Raley, assistant Interior secretary for water and science, was among a small group of researchers who rafted down the river during the experiment. By satellite phone from the canyon, he described the Colorado as “velvety chocolate and red,” with strong currents.

“There’s a lot of sediment in the river,” he said.

The flooding was intended to redistribute 800,000 metric tons of that sediment along the river to cover archeological sites, restore beaches and save fish and plants that have been disappearing since relatively sediment-free water began flowing from Glen Canyon Dam four decades ago.

The Interior Department began studying the effects of the dam in the early 1980s and discovered that beaches downstream from the structure were washing away. In 1996, officials flooded the canyon with water for 18 days.

Scientists overestimated the sediment levels in the beds of tributary rivers that pour into the Colorado below the dam, and sediment that was redeposited by some of the flooding was soon swept away.

The new flood was considered a refinement of the 1996 test.

“The Grand Canyon is terribly important, but so is power production,” Raley said, referring to the dam. “Any time man shows up, we have an impact on the environment. The challenge is how we manage that impact.”

The latest release from the dam is estimated to have cost just under $2 million in potential power generation, according to the Colorado River Storage Project office.

The controlled flood will not change the annual water release from Lake Powell, which the dam created, but it is expected to drain the lake somewhat in the short term. Chip Groat, director of the U.S. Geological Survey, said the Bureau of Reclamation would calculate the flood into the total water allotment for the year and adjust future flows.

About 50 scientists, including Raley, were on and around the river to study the immediate effects on the canyon.

Raley said new whirlpools had formed in several places along the river.

“It’s a massive and powerful river at any time,” he said. “But there are some places where you go, ‘Gee, I hope that doesn’t suck our boat down.’ ”