River 'flush' washes up new data
By Patrick O'Driscoll, USA TODAY
A man-made flood through the Grand Canyon last Thanksgiving shows promise in rebuilding beaches vital to recreation and the ecosystem on the Colorado River, federal scientists said Wednesday.
But the river still flushes out more sediment than it adds each year, the U.S. Geological Survey reported in a 220-page study of efforts to manage the canyon. That could lead to drastic measures, such as trucking sand from Lake Powell to remake sandbars downriver for endangered wildlife and increased numbers of river rafters, campers and hikers.
"It would be a very expensive option," said Denny Fenn, director of the agency's Southwest Biological Science Center, which oversaw the study.
Scientists hope last November's "flush" can be repeated and become a regular management tactic. The five-day experiment pushed downstream 1 million tons of sediment that had washed in from a side canyon just below Glen Canyon Dam.
The dam, built in 1963, blocks 92% of the sediment once swept down the canyon. It created beaches and backwaters where wildlife live and visitors play.
Since then, beaches have begun to disappear. So have some species. The latest study sums up years of protection efforts around operating the dam, which provides hydropower and stores water for droughts.
Next up: A less intensive test to see if smaller but more frequent releases can build beaches and still accommodate dam needs. Last year's flood was so big - peaking at 18.5 million gallons a second for 2 ½ days - that the water had to bypass the dam turbines.
Other findings:
• The canyon flush reclaimed some campsites lost to low river flows and lack of sediment. From 1998 to 2003, 55% of summer sites were lost to erosion and encroachment by vegetation.
• Asian tapeworms infect 90% of the Colorado's endangered humpback chub, an oversized minnow. Scientists aren't certain yet what effect the parasite is having, but Fenn called the news "scary." The number of humpback has declined up to 75% since 1989.
• Removing more than 18,500 non-native rainbow trout from a stretch favored by humpbacks may be helping. Trout, introduced decades ago for sport fishing, prey on young chub and other species.
• Prehistoric dwellings and sites important to native tribes are threatened by the loss of sand and more hikers. Wind-blown sand helps preserve the sites.
By Patrick O'Driscoll, USA TODAY
A man-made flood through the Grand Canyon last Thanksgiving shows promise in rebuilding beaches vital to recreation and the ecosystem on the Colorado River, federal scientists said Wednesday.
But the river still flushes out more sediment than it adds each year, the U.S. Geological Survey reported in a 220-page study of efforts to manage the canyon. That could lead to drastic measures, such as trucking sand from Lake Powell to remake sandbars downriver for endangered wildlife and increased numbers of river rafters, campers and hikers.
"It would be a very expensive option," said Denny Fenn, director of the agency's Southwest Biological Science Center, which oversaw the study.
Scientists hope last November's "flush" can be repeated and become a regular management tactic. The five-day experiment pushed downstream 1 million tons of sediment that had washed in from a side canyon just below Glen Canyon Dam.
The dam, built in 1963, blocks 92% of the sediment once swept down the canyon. It created beaches and backwaters where wildlife live and visitors play.
Since then, beaches have begun to disappear. So have some species. The latest study sums up years of protection efforts around operating the dam, which provides hydropower and stores water for droughts.
Next up: A less intensive test to see if smaller but more frequent releases can build beaches and still accommodate dam needs. Last year's flood was so big - peaking at 18.5 million gallons a second for 2 ½ days - that the water had to bypass the dam turbines.
Other findings:
• The canyon flush reclaimed some campsites lost to low river flows and lack of sediment. From 1998 to 2003, 55% of summer sites were lost to erosion and encroachment by vegetation.
• Asian tapeworms infect 90% of the Colorado's endangered humpback chub, an oversized minnow. Scientists aren't certain yet what effect the parasite is having, but Fenn called the news "scary." The number of humpback has declined up to 75% since 1989.
• Removing more than 18,500 non-native rainbow trout from a stretch favored by humpbacks may be helping. Trout, introduced decades ago for sport fishing, prey on young chub and other species.
• Prehistoric dwellings and sites important to native tribes are threatened by the loss of sand and more hikers. Wind-blown sand helps preserve the sites.
