Louis R wrote:Draining canals is generally impractical: you can only do at points where the canal bed is higher than the surrounding terrain, and only section by section between locks. Nothing the other side of a lock will be affected, although of course you can't get through them until that side is refilled.
That's not entirely true IMHO. I don't think there's any definitive TextEv for the configuration of the lock gates, so if they're like the lock gates of most English & Welsh canals (i.e. 1 gate each side of the canal forming a wedge against the upstream side) then wouldn't blowing the walls of the upstream canal cause the weight of the water on the other side of lock gates to force them open thus draining more than the current segment. (At least until the water level drops to the level of the cill at a set of locks, at which point the segment beyond there won't drain any further[1].)
[1] Well, excluding segments which have additional water inputs from other rivers and streams in which case draining at roughly the rate of new water input in that segment will continue.