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Manmade Flood to Nourish Grand Canyon Ecosystem

Posted by samzenpus on from the two-of-every-kind-of-tourist dept.

Dr. Eggman writes "The Associated Press brings us news of a flood in the Grand Canyon. This flood is no ordinary flood, however. This is a man-made flood released from the Glen Canyon Dam. The Dam is releasing four to five times its normal amount of water over the course of a three day artificial flood. Scientists are conducting this massive experiment in order to document and better understand the complex relation of the aquatic habitats, natural floods, and the sediment they bring. Floods no longer bring sediment to these parts of the canyon as the Dam keeps it locked up and released in small, drawn out intervals. The Dam prevents the floods from bringing the sediments in to replenish the sandbars and allow the river to maintain its warm, murky habitat rather than a cool, clear one. It is thought that this cool clear environment brought on by the dam is responsible for helping to extinguish 4 species of fish and push 2 more towards the brink. It is hoped that this terra-reformation experiment will positively impact the habitat and fish populations, warranting further artificial floods at an increased rate of every one to two years rather than the time span between the two previous floods and this one of 8 and 4 years."

6 of 56 comments (clear)

  1. enough sediment by peektwice · · Score: 4, Informative

    So there's enough sediment behind the dam to be a problem, and in the process of flushing it, they also can claim to be helping the canyon's ecosystem. Not to be a pessimist, but it looks to me like they're just flushing the sediment. They've done this twice before, according to TFA.

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    1. Re:enough sediment by Dr.+Eggman · · Score: 4, Insightful

      The natural state of the river did not, according to theory, see the average flow building up sediment, but rather from the sound of the article swept away more sediment than it deposited. It was the natural flooding of the Arizona monsoon seasons that deposited enough sediment to replenish the habitat, often enough to prevent species populations from collapsing. The artificial floods are meant to mimic those flood, every one to two YEARS (if the practice proves beneficial then on a continuing basis) and restore the habitats to a state similar to before the Dam. Removing the Dam is out of the question. Frankly, I'd be happy they're concerned enough to warrant the possibility of making this an annual event; considering the last two times this flooding occured just to flush out the sediment were in 1996 and 2004. 8 years and 4 years before they need to dump sediment for the Dam's sake, but purpose every year or two years for the environment's sake.

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      Demented But Determined.
    2. Re:enough sediment by Dr.+Eggman · · Score: 4, Interesting

      The flood is a three-day event, and "The water level in the canyon will only rise a few feet." Water flows regularly in the area, but its a flood event when an abnormally high volume of water is released over a period of time. Think of the Nile river floods of ancient Egypt; they weren't sweeping away everything in their path, but gently raising the water levels to consume the banks, depositing sediment before receding and leaving revitalized agricultural grounds to the Egyptian farmers.

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      Demented But Determined.
    3. Re:enough sediment by fredrated · · Score: 4, Informative

      The 'average' flow either deposited or removed sediment, depending on the amount of sediment already present when the flow occured. The Colorado River was named 'red' for a reason: it always carried a huge sediment load which it had picked up along the whole length of its run from the rocky mountains. The canyon and the river were in dynamic equilibrium: if the river was a little under in it's sediment load it would scour some from the canyon; if it had a little more than usual it would deposit sediment. The reason the Arizona monsoon has come to play a dominent role is because almost all of the pre-canyon sediment load is deposited at the head of lake Powell now, so now the only significant sediment is what is deposited by the Paria, the Little Colorado and other side canyons below the dam, when they flood during the monsoon. And that amount is pathetically small compared to what the river carried in the pre-dam period.

      The Arizona monsoon floods were not necessary to keep species from collapsing, the river always had a huge sediment load that was inimical to species like trout that need clear water. Thus there was basically no competition for habitat until Glen Canyon Dam turned the water clear. All that the artifical floods do is churn up the 'monsoon' deposited sediment from the bottom and move it up onto the existing and previously existing beach sites, benificial for plant and animal habitat. It does nothing for the hump-back chub because in very short order the water will run clear again. And the previous 2 floods have demonstrated that these newly deposited beach sands do not stay long. As long as the Colorado River through Grand Canyon runs clear it will scour and carry away sediment to Lake Meade.

      I am not sure what you mean in the sentence fragment "...before they need to dump sediment for the Dam's sake...", but no sediment is being removed from behind the dam. In fact, geologists estimate that it will probably be only a couple of hundred years before lake Powell is full of sediment and the dam will become a waterfall. The waterfall will then undercut the damn pretty quickly, as it has undercut lava flows in the past, and the dam will be gone.

      As for the articles comment that half the camp sites in the canyon are disappearing, this only refers to camp sites used by river runners. If you backpack in the canyon back country, the best place to go, you will find an unlimited number of camp sites.

  2. Re:I have a better idea! by Gay+for+Linux · · Score: 5, Funny

    Screw civilization, it's time to go back to being hunters and gatherers. Man things were awesome then, what with all the hunting and the gathering. And the even more hunting and the gathering. And life sucking.

  3. Challenge at Glen Canyon by ElDuque · · Score: 5, Interesting

    The Glen Canyon Dam was almost the site of a much larger flood in 1983, when it was nearly overtopped.

    http://www.google.com/search?source=ig&hl=en&rlz=&q=%22the+1983+flood+at+glen+canyon%22&btnG=Google+Search
    http://www.popsci.com/scitech/article/2003-03/water-vapor-almost-busts-dam

    The cavitation damage to the solid rock of the spillway walls was truly incredible.

    For an exciting telling of the story, search Google Video for "Challenge at Glen Canyon". (You will be instantly reminded of every National Parks visitors center you have been in.)

    http://video.google.com/videoplay?docid=-1358563539762136744