If it is, then shutting it down would cut off an enemy's economic resources and force them to choose between an angry population and attacking a fortified position against air superiority.
Yes, being without electricity does great harm to the civilian population, but less harm than a massacre-by-flood.
I am just guessing here, but I would expect that there are better ways to solve the issue with the gate that are easier, safer and even cheaper than dynamite.
The article says only one of two gates has problems, but they cannot open only one because of the asymmetry that would introduce. So, to solve the problem with dynamite, it would be necessary to make very good calculations to be sure you make exactly the hole you want, then actually do it with a very high precision (for an explosion).
I do not think opening that gate is as much a technical problem as a problem of initiative and responsibility.
Various forms of shaped charges and explosives could be used to open the sluice gates but that would leave them permanently opened.
The main fear here is that if the dam reaches its design head, the water will tunnel underneath and around the dam through the water soluble rocks. The dam can't exceed the design head because of the spillway that is visible to the south east of the dam.
So explosives could well be used to force open the sluice gates.
You (and at least one other) reacted as though I had claimed such an action would come with a guarantee nothing could go wrong. Which is, to put it bluntly, a rather stupid reaction given that:
1. I didn't make a claim. I asked a question.
2. According to the experts, the clock is currently ticking down on a million lives with no idea of how much time is left, so your implied suggestion of doing nothing (which is the implied suggestion when you summarily dismiss a line of thought while providing nothing in its place) is... well, how exactly would you describe the suggestion of just letting a million people die, had it come from someone else?
It just seems to me that using explosives on a structure where collapse is imminent in order to fix it sounds like the most dangerous idea one could possibly have.
First of all, according to what the experts are saying, the most dangerous idea one could possibly have is your idea of doing nothing - that guarantees the worst-case outcome.
Second, one would normally expect the force required to break the dam to be orders of magnitude larger than that required to open a sluice gate. Obviously this isn't a normal situation, but then, what are the figures? If a stick of dynamite isn't the appropriate tool, exactly what would it take to open the gates?
Third, if you could say 'we are going to try this at such and such a time, everyone be prepared' that would be far better than having it fail at an unknown time.
Fourth, now that I think of it, even deliberately blowing up the dam at a known time would be better than letting it fail at an unknown time.
Fifth, I'm sure there is some relevant idea or consideration I haven't thought of, that someone else could think of if they put their mind to doing so.
I would imagine siphoning might be a simple enough process and could be setup in multiple places along the dam to avoid the asymmetric draining issues mentioned further in the discussion here on hacker news.
"This siphon effect relies on atmospheric pressure to allow the pressure and pressure potential energy to drop as the water travels upward inside the sealed pipe. But eventually the pressure of the rising water reaches zero and no further reductions in pressure and pressure potential energy are possible. That failure of the siphon effect occurs when the water is about 30 feet (10 meters) above the higher container. You can't use a siphon to lift water higher than 30 feet because above that height, an empty region will develop at the top of the pipe and stop the siphon process."
Putting aside the obvious detail that the dam would be empty already if we were trying to siphon water up a full 371 feet... Your correct, the entire thread this spawned was educational, and I learned something new today which was pretty damn interesting. Interesting enough I'm not bothered by the small karma loss my initial comment incurred.
Actually though, you could presumably cut holes in the dam as you go. So siphon off the top 30ft, then cut a hole at 341 feet and siphon through there.
That's called a spillway BTW and the problem with spillways is erosion and the energy of the water. So spillways have to be made of reinforced concrete or similarly strong materials when the local rock isn't hard enough and they have to be shaped to dissipate the energy.
The spillway of the Mosul dam is made of concrete the problem with it appears to be that it allows too high a water level for the dam in its current shape even when fully open.
I'm not sure it would be quite so simple. The article mentions the reason that they can't just open one gate is because the asymmetric draining would be harmful to the dam. It's possible that any sort of adhoc draining would adversely affect the dam. Not to mention quickly building a secure tunnel to handle the water pressure at that depth sounds like no mean feat.
Well, immediately getting back to grouting the base would be the first order of business. Second, fixing the jammed sluice gate. We need an analysis and timeline of the above and time is something it seems we don't have.
Easy to say when the sluice gates are stuck and the dam represents more than 10% of the country's already way under demand electricity production.