I remember 1976 and there was a lot of bad feeling in Wales because we were water rationed but people in Birmingham weren't because they had Welsh water
I see it every day 
The back story to that, is that the people running Birmingham back in the late 1800s/early 1900s were a bit odd and pretty competent at running a big city (thank goodness we don't have any weirdoes like that now, imagine the chaos !).
So when Birmingham was expanding, the council planned ahead and secured a lake in Wales (which, by the way was paid for by the City of Birmingham) and build one of the countries longest aqueducts to bring it to Brum.
The result is that Birmigham - certainly the areas served from the Elan Valley in Wales - have 100% water security.
Any other city in Britain could have done it too. Just they clearly had different priorities like gold chains for the mayor or somesuch.
That's what running a city should be about.
The people of Wales would have better directed their anger at their own politicians who were happy to take (a lot) of money from Birmingham, and clearly not invest it in their own infrastructure. Why should Birmingham be slighted for having the foresight and political will to provide for it's citizens ???
en.wikipedia.org/wiki/Elan_Valley_Reservoirs
(few Brummies know the above by the way. Which is a tribute to the quiet efficiency of it)
Of course, in a wider sense, all this shows is that water management isn't black magic, but simple engineering, and that 80% of the reasons why it doesn't happen will be political/social or economic - not geographic or geologic.
The Romans were probably better at water management than some countries today. Somehow they managed to run an entire empire from Portugal to Palestine and Scotland to North Africa (well into North Africa) for 400 years, with few water issues (interesting supposition about Palestine upthread).