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From the discussion and video, would it be accurate to say the backup lake is too small to contain enough water to prevent flooding upstream, and then the dam has to discharge the water and flood downstream to relieve upstream flooding and prevent dam failure?

What would have happened if the dam wasn't there and this amount of rain occurred?
 
Posts: 2106 | Location: Indiana | Registered: December 28, 2004Reply With QuoteReport This Post
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If I read this right the Chinese blowing the dam just killed 100 people downstream??

"China blasted a dam over a river in Anhui province on Sunday to discharge the surging flood waters as torrential rains and floods wreaked havoc in the country, killing over 100 people.

The dam on the Chuhe river, a tributary of the mighty Yangtze River, was destroyed with explosives to ease the flood control pressure in the river basin, state-run CCTV reported.

Water levels on many rivers, including the Yangtze, have been unusually high this year because of torrential rains. The Three Gorges Dam on the Yangtze last week opened three floodgates as the water level behind the world's biggest dam rose more than 15 metres above flood level.

Last week, official media reported that over 140 people were killed or missing since June. On Sunday, China's national observatory renewed a yellow alert for rainstorms, as incessant downpours would continue to wreak havoc in vast stretches of the country."

LINK




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Posts: 5135 | Location: District 12 | Registered: June 16, 2012Reply With QuoteReport This Post
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quote:
Originally posted by ChuckFinley:
If I read this right the Chinese blowing the dam just killed 100 people downstream??



I read the same thing on a different channel today & it looked to me like they were summarizing the death toll over the last couple weeks.

The only video I could find that purported to show the dam that was blown was an earthen dam that seemed to be almost entirely covered already, could have been a bad vid link tho.



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Posts: 1675 | Location: Fort Lauderdale, FL - its a dry heat....... | Registered: January 26, 2001Reply With QuoteReport This Post
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This video talks about the chinese opening dikes to flood secondary holding areas. It claims if the chinese government gives warning in advance they're liable for the damage. If they claim a natural disaster then they're not.

Sounds like something a despotic government would do.

quote:
Villages in flood reservoir area sacrificed to save big cities | China Flood | Yangtze River

https://www.youtube.com/watch?v=VhpSFEevfxw


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Posts: 12458 | Location: Bottom of Lake Washington | Registered: March 06, 2007Reply With QuoteReport This Post
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Has the flooding started to go down?




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Posts: 16967 | Location: Northern Virginia | Registered: November 08, 2008Reply With QuoteReport This Post
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quote:
Originally posted by Lefty Sig:
What would have happened if the dam wasn't there and this amount of rain occurred?

Theoretically, localized flooding up and down the river. The big deal with a dam is that it stores up (a massive volume and weight of) water, so a sudden release is likelier to be catastrophic.
 
Posts: 24476 | Location: Deep in the heart of the brush country, and closing on that #&*%!?! roadrunner. Really. | Registered: February 05, 2008Reply With QuoteReport This Post
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quote:
Originally posted by Fenris:
Has the flooding started to go down?


no

one of the videos said another heavy amount of water is supposed to arrive tomorrow

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Posts: 8028 | Location: Florida | Registered: September 20, 2004Reply With QuoteReport This Post
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Lefty Sig

Dams serve to modulate water flow, or, if you'll excuse the expression right now, flatten the curve for downstream water. Without the dam, excess rainfall leads to localized flooding that works its way down the river as the whole system slowly drains toward the ocean. What the dam does is retain some of that flood water and release it in a controlled manner so that there is no downstream flood. That's the goal anyway, as well as to generate power from the hydraulic head.

However, flooding as bad as what they've seen in China basically renders the dam useless as a flood control device, at least temporarily. Once the water level in the reservoir behind the dam reaches the safety threshold (maximum pool), the dam has to pass through all of the upstream water that comes to it or risk structural failure. Once the water levels begin to drop, the dam will begin to function again for flood control and slowly discharge the excess reservoir water.


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quote:
Originally posted by jaaron11:
Lefty Sig

Dams serve to modulate water flow, or, if you'll excuse the expression right now, flatten the curve for downstream water. Without the dam, excess rainfall leads to localized flooding that works its way down the river as the whole system slowly drains toward the ocean. What the dam does is retain some of that flood water and release it in a controlled manner so that there is no downstream flood. That's the goal anyway, as well as to generate power from the hydraulic head.

However, flooding as bad as what they've seen in China basically renders the dam useless as a flood control device, at least temporarily. Once the water level in the reservoir behind the dam reaches the safety threshold (maximum pool), the dam has to pass through all of the upstream water that comes to it or risk structural failure. Once the water levels begin to drop, the dam will begin to function again for flood control and slowly discharge the excess reservoir water.

A real world metaphor for Minsky's theories that policies intended to minimize economic risk may reduce the frequency of crises but increase the magnitude of downturns, as risks accumulate to the point that once triggered, the consequences are truly calamitous.




The budget should be balanced, the Treasury should be refilled, public debt should be reduced, the arrogance of officialdom should be tempered and controlled, and the assistance to foreign lands should be curtailed lest Rome become bankrupt. People again must learn to work, instead of living on public assistance. ~ Cicero 55 BC

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Posts: 16967 | Location: Northern Virginia | Registered: November 08, 2008Reply With QuoteReport This Post
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Once the water level in the reservoir behind the dam reaches the safety threshold (maximum pool), the dam has to pass through all of the upstream water that comes to it or risk structural failure.

At that point the question becomes can they release enough water to keep the water level from rising beyond the safety threshold?
What if new water is coming into the pool faster than they can release it?



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Posts: 18497 | Location: St. Louis, MO | Registered: April 03, 2009Reply With QuoteReport This Post
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Which would be why they blew up that other dam.
 
Posts: 24476 | Location: Deep in the heart of the brush country, and closing on that #&*%!?! roadrunner. Really. | Registered: February 05, 2008Reply With QuoteReport This Post
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Thanks for the explanations. So if they had made that lake deeper to hold more water, maybe they would be better off? But that would mean a bigger dam, right?

Just remember, official CCP disaster death tolls are an order of magnitude or more understated. So that 100-some number is really 1000-some.

For example, a mine caves in and and more than 100-200 miners never come home. Doing what digging they can, they find 13 bodies. Therefore, the death toll is 13. No body, no death. This happened in a friend's hometown.
 
Posts: 2106 | Location: Indiana | Registered: December 28, 2004Reply With QuoteReport This Post
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i read its the largest electricity producing dam in the world

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Posts: 8028 | Location: Florida | Registered: September 20, 2004Reply With QuoteReport This Post
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Not for long. More rain in the forecast.


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Sad for folks downstream. Karma for the ccp regime.
 
Posts: 2198 | Location: newyorkistan | Registered: January 06, 2008Reply With QuoteReport This Post
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quote:
Originally posted by chellim1:

At that point the question becomes can they release enough water to keep the water level from rising beyond the safety threshold?
What if new water is coming into the pool faster than they can release it?


Those are good questions. I would think during the design phase of a dam, you'd look at the worst projected inflow volume case, then double it. Design the outflow capability to that value, something like that. Not being able to release water fast enough would lead to a complete dam failure eventually.

I don't see how blowing up other dams, either upstream or downstream would help the problem at Three Gorges. You would want more upstream dams to help slow the water down if possible, not fewer.


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Posts: 428 | Location: Missouri | Registered: October 17, 2010Reply With QuoteReport This Post
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quote:
Originally posted by JoseyWales2:

I don't see how blowing up other dams, either upstream or downstream would help the problem at Three Gorges. You would want more upstream dams to help slow the water down if possible, not fewer.


I assumed the dams that they blew were not actually on the Yangtze but were dams on distributaries of the Yangtze upstream of the Three Gorges dam.


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Posts: 24618 | Location: Ski Town, Utah | Registered: October 29, 2012Reply With QuoteReport This Post
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I don't see how blowing up other dams, either upstream or downstream would help the problem at Three Gorges. You would want more upstream dams to help slow the water down if possible, not fewer.


I'm guessing the theory is to blow dams in other out-flowing rivers from the upstream body of water, thus lowering the amount of water going to the main dam.




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Posts: 35266 | Location: NW Indiana | Registered: November 22, 2002Reply With QuoteReport This Post
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quote:
Originally posted by Lefty Sig:
Thanks for the explanations. So if they had made that lake deeper to hold more water, maybe they would be better off? But that would mean a bigger dam, right?
.

Not quite that simple. I think you're envisioning a giant bowl of sufficient height all around to contain another foot, 3 feet, whatever, of water.

Look at the topography on almost any lake of size and you'll see that's not at all the way they work. If you snapped your fingers and made a damn a couple feet higher you have to look at every single foot of shoreline that is within 2 feet of full pool. If there is one, let alone dozens, of places where that height is 1' higher and you put in another 1.5 feet, you then are flooding additional area behind wherever that is. If it's isolated to one or a few spots suited for another retention method no problem. But if not, you've greatly expanded the area beyond current footprint.

Even if you could, the load on the existing dam is now MUCH greater due to the expanded area and the impact on the entire dam structure.

You also can't just build a small simple dam to stop that "leak". If you were building to bring up level by one foot that's pressure from that one foot over an enormous area all coming to bear on that spot. I think - I'm a little less certain on the physics of that. Probably actually much less at surface of water than as you progress downward, butit's not zero.

Either way, it's dam complicated.

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https://watchers.news/2020/07/...bs-to-more-than-150/







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