Dam Solution?

Back to the original story about the dam for a moment.

A friend has just shown me this youtube link via his Facebook page. I thought it worth 11 minutes of my time.

Also as of 05/08/19 this has just popped up on one of my local Facebook groups

"Update: 5:50pm. Staff levels at the dam have dropped by 70% . The army and fire services have left and maybe no more than 40 personnel are on site.
We've had vast amounts of food delivered to Whaley Hall & the sailing club today and no doubt as much at Chapel school n the sports club in Whaley.
Plans for dispersal of non perishable goods are in place for a gesture towards people being repatriated to their homes when the crisis is over. "

From my earlier calculations, with the water level at the top of the dam a 0.5m syphon will give a flow of 1480 gal/s (24 million litres/hr). Once the water level has dropped by 10 feet this flow will fall to 1300 gal/s.

I have tried to find the capacity of the pumps being used without success. 24 million litres/hr sounds like an awful lot. However if the bore of the pipe was 1" the flow would be 3.7 gal/s which seems sensible.

JA

These from Hereford and Worcester are 7000 litres / Minute apparently

i.e. 420,000 l/hr and there were at least 23 of them working at one time so about 9.6 million l/hr

Bill

Edited By peak4 on 05/08/2019 19:27:11

Ah but, if you just have a syphon, once it empties the dam down to the level of the intake it will suck air and stop working, so you either need an air pump to re-prime the system, or a valve to stop the flow before it gets too low.

Also, the dam is 24m deep (to the water level, never mind the extra height of the wall), so you can't empty it with a syphon anyway

To go off on another tangent (who me?) if the pump design was sufficiently clever and the outlet is well below the inlet, once it is running you could use the pump as a water turbine and use the motor as a generator

I am not sure if I am right or wrong!

Sorry, I am getting old.

JA

Edited By JA on 05/08/2019 20:33:02

At 7000l/s the velocity in the 150mm / 6" pipe the pump sets have, would be about 1.13m/sec. ie in the normal range of 1 to 3m/s pipe velocity.

for the syphon at 1480 gps is 88800GPM so allowing 18" pipe (500mm as suggested the velocity would be 35m/s

So two questions

how thick does the pipe have to be to resist erosion?

How do you stop it working as a water jet cutter at the discharge?

And in the time we have been speculating on this they have mobalised the pumps and drained 50% or the water

Steve

I noticed in the Wikipedia entry for the dam that a proportion of the water feeding the dam is diverted into the stream alongside. I assume that steps have been taken to divert all the incoming water into the stream and that it can handle the increase.

That I think is another aspect of the problem.

There were already flood warnings in place in the area due to heavy rain making this a bad time to add another million tons of water to the outflow. Emptying the dam would have to be managed to avoid bursting banks downstream. There's nowhere else for the water to go apart from into the valley.

Dave

If there is increased rainfall in the area, it will go downstream whether or not the dam exists. Normally the dam would be full and overflowing. They may have to stop pumping if the rain starts in earnest, but there will now be a period of respite before the level rises back to danger levels. That bypass channel on the north side of the dam is of vital importance now.

From what I have seen (but can't now find to link to), the only outflow is into the canal system, not the river. Canals are not built to handle high flows. The only way to get a large volume out in a hurry was to take it over the top of the dam, which does take it into the river.

The first Chinnok loads before they started on the slipway were to dam the infeed.

Steve

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I'm not suggesting it would be a practical idea, Duncan ... but I'm struggling to understand your assertion.

Please look at the elevation profile that I linked on the 'What did you do today ...' thread when it all started.

[quote]

See the Google Earth & Elevation composite on this BBC page:

**LINK**

[/quote]

MichaelG.

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Edit: or check the contours on the OS Map 

Edited By Michael Gilligan on 06/08/2019 21:57:02

What is this reservoir for?

The canal.

The Marple locks were closed earlier this year for repairs, so the level in the reservoir built up, unlike last year.

I would suggest that had the Marple locks not been closed this year, none of this would have occurred.

I don't know why the canal system hasn't been used to drain the reservoir.

A simple online search indicates the reservoir has been causing problems for many decades.

Cheers,

Julian

Water being discharged from a pipe gave Me the idea of, why not have a generator hooked up to supply electricity to run other pumps? Might help on remote locations. Lights to work at night, cook meals etc....

What you are suggesting is a sort of hydro-electric system, flowing water turning an impeller attached to a generator (well used and understood technology), however there are losses involved in generators and motors so better to use the discharging water to drive an impeller directly coupled connected to a pump. That pump will produce a flow of water from its output so that might as well be harnessed to drive another pump.... ad infinitum...

Do you realise that you have stumbled on to perpetual motion

Ian P

Going right back to Neil's original suggestion, I wonder if he has really thought it through? So OK, we know now that a big enough siphon pipe could shift enough water to help...but how does he plan to get the siphon started? I don't think any of us have a thumb big enough to block the end of the immersed pipe, nor would sucking on the bottom end be much fun. So it seems to me that getting the siphon started is going to need a big pump. So since you are going to need a pump anyway, why bother trying to set up a siphon?

John

Using a siphon would only require energy to prime it then it would run for free.

Cheers Michael

Slowly it dawns on me the difficulties with a syphon.

You will need a large diameter rigid pipe of that runs from near the bottom of the water side of the dam to the bottom of the dry side. All the joints in the pipe above the water level in the dam must be absolutely leak free otherwise the syphon fails. The pipe work will need to be restrained to prevent movement due to change of direction of the flow (restrained using the failing dam?). The water from the dam will be exhausted at the bottom of the dam instead of any side spillway. As already mentioned priming a big syphon is not easy. The time transporting and assembling such a device would be slow compared with bringing pumps from the River Severn which can just be dumped on the ground, hoses run out and started very quickly.

JA

Or a few hundred domestic hose pipes and one guy with good lungs to suck on them in turn...and a big banner 'sponsored by hozelock'

pgk

I thought I had found a helpful explanation of the syphon/siphon here: **LINK**

https://www.physicscentral.com/experiment/askaphysicist/physics-answer.cfm?uid=20080512104921

...bur I'm struggling to comprehend this statement:

[quote]

Moreover, the pressure of water in a sealed pipe decreases with altitude, so the higher you look in that pipe, the less pressure potential energy you'll find. Because of this pressure effect, the total potential energy (gravitational plus pressure) of water in a closed pipe doesn't change, even as that water rises a short distance upward inside the pipe!

[/quote]

Two nations separated by a common language ? ... or am I just being thick ?

I will have some coffee !!

MichaelG.