Manmade Flood to Nourish Grand Canyon Ecosystem

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."

Comments

enough sediment

[peektwice]

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.

Re:enough sediment

[Dr. Eggman]

Don't know if I should reiterate this or not, but the last dump was in 2004 and the one before that was 1996. It hardly seems as though they need to dump sediment again for the Dam's sake after 4 years if the previous dump span was 8 years. Furthermore, the article proposes the possibility of annual or biannual dumps, if the restoration attempt proves beneficial to the fish habitats.

Re:enough sediment

[fredrated]

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.

And also see the other side..

[Anonymous Coward]

Not saying its all wrong, but it does not harm to consider the criticism as well.

" Far from restoring crucial sand banks and other areas, the flows could destroy habitat, [Grand Canyon National Park Supt. Steve Martin] said. One flood was not enough, Martin said Monday. Holding off follow-up flows for months would leave endangered humpback chub fish, sandbars used by river rafting trips, and archaeological treasures at river's edge diminished "almost to the point of no return," he said."

Re:Don't worry about it

[AngelofDeath-02]

And of course, then there's the theory that global warming affects the ocean currents, that distribute the warm and cold climates, causing winters to be milder, and summers cooler ...

Thats why here in AZ I wore a t-shirt Clear till Mid January. Oh ya.. I'm wearing a T-shirt now, too =)

Anyway, I think its too early to dismiss global warming like you are doing. I agree that the earth is robust, but seasonal extremes is one predicted outcome of this scenario.

Re:How is this different from ....

[Dr. Eggman]

Its not so much about the volumes of water we are trying to bring downstream, in fact the Dam does regularly release water downstream (hence its function as a dam and not a reservoir barricade.) Instead, its about the material brought along with the water flow. The amount of sediment deposited by the regular flow is not enough to offset the sediment swept from the sandbars and it is hoped that periodical flood volumes of water would deposit much more sediment, enough to offset that which it takes as well as the regular flow takes. As you'll notice, although a larger volume of water is released in the artificial flood, the flow does not reach much farther up the sandbars than the regular flow.

Re:Don't worry about it

[thestuckmud]

Nature isn't easily effected by man.

On the contrary, most biologists believe we are in the beginning of a period of primarily anthropogenic mass extinction, called the Holocene extinction event. Whether or not we choose to say this effect was achieved "easily", it is already substantial.