The US Army Corps of Engineers (USACE) uses Tainter gates in all but its oldest river dams.
Newburgh Dam on the Ohio River
I made a special trip down the Illinois River during a flood take photos of the Dresden and Marseilles Dams during a flood. Below is a photo of the Marseilles Dam. Note that the first four gates are completely out of the water, and the river has an unobstructed flow. Also note that gates 6 and 7 are raised but no water is flowing. That is because bulkheads have been installed in those openings. They are still repairing the dam after the April, 2013, accident. There is a crane on a barge parked behind the dam on the left side of the river.
|20150714 2760, DeBruler|
A satellite image of the USACE using their Hercules 60' ringer crane to repair a gate gives us the unique view of a gate laying on a couple of barges that have been lashed together.
Control works for the Marseilles North Mill Headrace
|Photo referenced by EngrColoState|
Just one gate is opened at a time to reduce how quickly the downstream river level rises. They want to avoid creating a flash flood that would not allow fishermen, kayakers, etc., time to get to higher ground.
I've noticed that active spillways for large dams are a good source of "white noise."
(new window) The spillway volumes for the Hartwell Dam looked impressive until I realized how tall the gates are. The pivot point is at the top of the concrete pillars. In some scenes, you can see the three beams that go from the trunnion to the gate, and the beams for the open gates are not much higher than for the closed gates. When you look at the height of the training wall on the side, the gates cannot be raised much higher or the water would go over the top of the wall.
Another test of Hartwell Dam test five years after the above test.
(new window at 2:41) At 3:44 the gates jump into focus. But you still can't see much difference between the top of the opened gates and the still closed gates. You can tell by the turbulence at the outflow of the hydro plant that they did not have to shut it down during this (partial capacity) test.
(new window) Logan Martin Dam
So why are reservoir gates so tall that only a fraction of their height is used at the bottom? If you know, please comment.
Here are some of my speculations:
- The gates are cheaper than the concrete needed for a higher spillway.
- They want to release the cooler water that is lower in the reservoir.
- The spillway has to deal with a lower head of water. But this is offset by the higher pressure of the released water.
- If it is the spillway for an earthen dam, they are willing to open the gates really wide if it proves to be necessary to keep the water from topping the earthen part. A check zoom out of the Harwell Dam reveals that it is an earthen dam.