Siphon for moving sediment and water over dam

[Wes41]

We are looking at using a siphon to move about 3cfs of water over a small dam. We want to continiously entrain the suspended silts and clays and also pull the fine hydrated clays off the bottom of the reservior.

Plan on doing a pilot study to see if it is feasible. We want to use 2-4 inch PVC hose for the test and similar materials for the permanent system.

Considering eductors or a vacuum blower with a water knockout device to prime the system. How high can a siphon lift water? Our maximum lift above the water surface would be about 10 feet, but we may could find a lower lift with a longer pipe run. We have about 20 feet of "head" below the water surface onthe back side of the dam. Total run of pipe in the 50-80 foot range. Water depth behind dam is about ten feet. The permanent solution could include lower lift heights by putting a connection through the steel floodgates. We are thinking portable/flexible pipes that could be removed during high flows that cause the diversion dam to rapidly fill with sediment and would bury the pipes.

A hydrologist and a hydrogeologist are attacting the problem without any flow/piping engineers. Do we need to find some engineering help? Any references you could point us to on siphons?

 

[BRIS]

There is plenty of data around on design of air regulated siphon spillways - USBR design of small dams etc.

But it looks like you are looking at a suction dredger utilising gravity to provide the suction.

I suggest therefore that you also look at dredging technology.


Most hydraulic text books will give you the basic principles of how a siphon works. The limit on a siphon lift is atmospheric pressure - vapour pressure. For water the maximum you can lift is about 8.0m.

It would appear that your driving head is 10 ft (difference between upstream and downstream water level) This will give you a velocity of 10 ft/sec with 80 ft of pipe.

I expect you will have to increase the flow to more than 3 cfs to get realistic results.

Yes you should consult a specialist

Brian



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