There is one thing I don't get it.
If it's a canal , man made , doesn't it have already some debit control gates built in?
Why the hell do they have to build a dam?
Judging by the sat images, there is one here, at the start of the canal:
Paste into Google Maps search: 46.759748, 33.398324
They can't just close the dams, though. In the CabMin meetings Turchinov proposed cutting off water supplies by blaming construction/maintenance works.
Hmm , just realized that if they cut the water supply there at that point all the ukr land after the gates will suffer also.
However the head of Kherson Regional State Administration, Yuriy Odarchenko, claimed that the newly built dam is related to construction of a “water metering station” which “will be finished soon” and will give precise measurement on the “amount of water that will be transferred to the Crimean peninsula,” RBK Ukraine reported.
The excuse is there already , although let me say that it kind'a makes sense.