PHOENIX - For the third time since 1996, officials plan to unleash a manmade flood in the Grand Canyon next month in an effort to restore an ecosystem that was altered by a dam constructed on the Colorado River decades ago.
When Glen Canyon Dam and Lake Powell were constructed it changed the flow of water through the Canyon. Waters released by the dam are usually from the bottom of Lake Powell, where temperatures are cooler. Silt and sediments are trapped by the still waters of Lake Powell and they do not flow down the Colorado into the Canyon. The Water flowing through the Canyon is, therefore, cooler and less muddy than it was before the Glen Canyon Dam was constructed.
So what, you ask. The water is clearer and cooler. Big deal.
Ah, but it is a big deal to the native species that grew up in that warm muddy water and depended upon the silt and sediment to provide nutrients and sand bars.
Without spring floods to flush the system and help rebuild beaches and fish habitat, native species suffered even as non-native fish thrived. The shift helped speed the extinction of four fish species and push two others, including the endangered humpback chub, near the edge.
Okay, you got that. Several species of fish have finned their way off this mortal coil because the dam has altered the ecosystem where they lived. (Apparently the Grand Canyon is the only place they lived.
What to do about those that are still threatened? Why, create a replica of the annual spring floods, of course. That ought to do the trick!
If approved by the U.S. Department of the Interior, next month's flood will scour and reshape miles of sandy banks on the floor of the Grand Canyon. The department's decision is expected this week.
If approved, flows in the Grand Canyon would increase to 41,000 cubic feet per second for nearly three days — four to five times the normal amount of water released from the Glen Canyon Dam. What scientists and environmentalists want to see is what will happen to the fish and the canyon when the gates close at dam and the staged flood recedes.
As the headline says, they’ve done this twice before starting in 1996. Huge amounts of water are released from Glen Canyon Dam. It scours the Canyon and reshapes the sand bars and beaches in the little nooks and crannies. No word of how the fish fare, Do they get flushed as well, like some belly up goldfish won at the local carnival?
Where’s all that “flushed” material go? Why to the next impoundment downstream, of course. That would be Lake Mead. You know, the major electrical for Las Vegas and water source for half of the southwest. No mention of the troublesome sedimentation filling Lake Mead, however.
According to an article in the Goat, a High Country News blog:
Lake Powell, on the Arizona-Utah border, was created to benefit Colorado, New Mexico, Utah and Wyoming. Three hundred miles away, on the Arizona-Nevada border, Lake Mead stores Colorado River water for Arizona, California and Nevada
So water will be pulled from one groups supply and dumped (along with lots of mud and other rubbish) into the holding tank of another group. Doesn’t sound so bad, especially when BOTH reservoirs are only at about half their capacity do to 1) drought and 2) over use. (The former problem may be alleviated slightly this spring when all that snow in the Rockies melts. See: Wet Snowpack Holding for Now from February 22, 2008 for an idea of what the problem might be come April and early May—Hint: it won’t be drought. “…over a wide area of the Rocky Mountains. Statewide, the snowpack is 132 percent of normal, with the highest levels recorded across the southern half.”)
Hopefully, the current snowpack will be absorbed by both the reserve capacities of the manmade lakes all up and down the western rivers and the thirsty soils of the agricultural areas. Otherwise, we’ll be reading about gargantuan flooding along the Missouri and Mississippi Rivers—again. (Who am I kidding? There will be flooding as there is every spring whether the snowpack is above or below average. With some luck, however, the melt may be a long, slow event and there won’t be the serious flooding that occurs from a rapid warm spell.)
See The Future Is Drying Up, published in the NY Times last October 21, 2007, for an interesting look at the usage of and claims upon the water supply in the American southwest.
Also from the NY Times of December 10, 2007: Western States Agree to Water-Sharing Pact
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