Where I live our water supply is pumped by electricity, so losing electricity means losing fresh water. But hey, at least it's not like the UK government is about to do anything reckless.
In Kempton steam museum they have the old backup generator which was actually powered by a water turbine from the mains supply (so indirectly powered by the steam engines). I'm hopeful that the modern system has at least as good redundancy but I wouldn't bet on it either.
