> This implies a degree of incompetence or corruption on the part of the dam designer and/or dam builder.
Of course it does!
In Laos/Cambodia, the dams are mostly built by China in order to help them build their silk road to Sihanoukville (so that they can have an easier route to Africa). In Vietnam, it is just plain greed since they aren't in as much of a rush to help China.
Unless you ride a motorbike into the furthest remote areas of these countries, like I have, you wouldn't be the wiser. I've see it all.
This implies a degree of incompetence or corruption on the part of the dam designer and/or dam builder.
I won't say such things never happens, but it is what not being able to predict and design around a regular change of season implies.