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PRI's Environmental News Magazine

Flooding the Grand Canyon

Air Date: Week of June 21, 1996

Earlier this year the U.S. government unleashed a portion of the Colorado river and flooded the Grand Canyon in order to help it recover from erosion. Other unanticipated discoveries were found along the way. George Hardeen reports from Arizona.

Transcript

CURWOOD: This spring, Federal officials cranked open the floodgates of the Glen Canyon Dam in Arizona to send a wall of water down the Colorado River and through the Grand Canyon. The idea was to stir up sand and sediment from the bottom of the Colordo and restore the numerous sandy beaches that had eroded away in the last 35 years since the dam was built. Now, as the waters retreat, scientists are starting to find out whether their experiment to help restore one of the world's most prized ecosystems worked. George Hardeen has our story.

BABBITT: This is a new beginning for the Grand Canyon and a new beginning for the way we manage this entire Colorado River system. So here goes.

(A door shuts. A klaxon, followed by mechanical sounds.)

HARDEEN: With the 710-foot high Glen Canyon Dam looming overhead, Interior Secretary Bruce Babbitt turned a valve to open the first of 4 8-foot wide bypass tubes, unleashing billions of gallons of water into the Colorado River.

(Water pours)

HARDEEN: As water gushed from the dam, enough to fill the Rose Bowl in 2 hours, 100 scientists waited downstream along the 300-mile length of the Grand Canyon to study the effects of a week of flooding.

WEGNER: The real objective here is trying to replicate as much as we can what Mother Nature would have done.

HARDEEN: Dave Wegner is director of Glen Canyon Environmental Studies, the Bureau of Reclamation office coordinating the research.

WEGNER: Historically, and that's pre-dam, floods would come in the spring time and erode beaches away. But as the waters receded in the spring, the sediment that had been picked up by the floods during the runoff would drop that sediment out then and rebuild those beaches.

HARDEEN: That changed 33 years ago when Lake Powell began filling up behind the Glen Canyon Dam. Millions of tons of sediment that used to replenish Grand Canyon beaches every year were held back. Annual spring floods that kept the river corridor scoured clean of most vegetation were halted, too.

(Footfalls on gravel)

HARDEEN: It wasn't long after the dam was built before hikers and river runners noticed environmental changes, primarily massive beach erosion along hundreds of miles of the Colorado River through the Grand Canyon. And fast-growing tamarisk and other non-native trees colonizing the river banks. For 30 years the dam was operated only to produce valuable hydropower to meet peak electrical demands of downstream consumers, rather than with any concern for the canyon's environment. As power was needed, more water was released, saturating sandy beaches. When power demands fell, water from the dam was quickly cut back allowing heavy, wet beaches to fall into the river and be carried away. This experimental flood was meant to rebuild those eroded beaches and wash away some of the invading trees. Larry Stevens is a river ecologist for Glen Canyon Environmental Studies.

STEVENS: That part of the flood has been tremendously successful. Lots and lots of sand deposition, new, big, high beaches being, having been formed by the flood. We got on the order of 5 or 6 feet of new sand on a lot of sites all the way through the canyon.

HARDEEN: In the first 61 miles, 55 new beaches were created with some gaining as much as 12 feet of new sand. The flood also dredged out backwaters that had filled in along the river. These are warmer, slow water areas which endangered native fish like the humpback chub, speckled dace and razorback sucker need to raise young. Yet the high water wasn't good news for every endangered creature. The Kanab ambersnail exists only here in its small lakes near Kanab, Utah. The flood washed away about 10% of its habitat here, but not before scientists marked and moved every snail in the path of the flood. And US Fish and Wildlife biologist Vicki Maretsky says in preparing for the flood, researchers found a new threat to the ambersnail.

MARETSKY: We've discovered a new predator on the snail in the area, which we hadn't anticipated. We'd been expecting things like beetles or maybe other snails or something like that, but it turns out that there are deer mice in the site, which seem to be able to grab the snails while they're active and moving around and just sort of pluck them from their shells.

HARDEEN: Dr. Maretsky says biologists will continue to monitor the mice, but that they probably don't threaten the snail population. Analysis of the flood data and aerial photography will continue through the summer. Tom Moody is a Grand Canyon river guide and consultant for the Grand Canyon Trust.

MOODY: We hope that we can learn, that the scientists can learn how these processes work well enough that we can use this as a valuable, viable management tool.

HARDEEN: Scientists will try to figure out how often a flood like this may be needed, how long it should last, and how much water should be released to rejuvenate the system next time. This first flood follows a 1992 law that changed the way the dam is managed and protects the canyon's environment. For years, power distributors and users resisted altering the dam's operation because of the costs. But among other benefits of this flood, researchers found the positive effects occurred in only 2 days rather than an entire week. That means the cost to power users for future prescribed floods will be millions of dollars less. Tom Moody says this flood's success demonstrates that a balance can be found between environmental and energy concerns.

MOODY: It's a significant event in that instead of fighting the effects and impacts of these large dams and western rivers, that we're actually working with the Bureau of Reclamation, working with the water users and the Upper Basin states to utilize the dam to restore and enhance the downstream resources.

HARDEEN: The flood had one other job to accomplish. Eleven years ago water flowing from the dam uncovered prehistoric Indian ruins and artifacts. The discovery of these relics was a reminder of how important the canyon has been to Hopis for millennia. Now, to protect these sites from the elements and vandals, 8 Indian tribes, including the Hopis, asked that this year's flood be allowed to re-bury them. Hopi religious leader Dalton Taylor.

TAYLOR: The Grand Canyon means a lot to Hopi, because our ancestors went through here. And my uncles and my fathers and other old timers, they tell me, if you ever visit any site, look for this symbol. And sure enough when we were at there, it's right there. So I tell them, this is Hopi. No doubt about it.

HARDEEN: While several sites were stabilized during the flood, scientists won't know until later this summer, when the spring runoff ends and the river level drops again, exactly how many of these cultural resources were saved. For Living on Earth, I'm George Hardeen in Tuba City, Arizona.

 

 

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