Coming from Australia, where we've recently come off a 10-year drought, rationing drinking water is far from the next thing. Before you ration drinking water, you ban or ration washing cars, watering lawns, and laundry.

Lawns in particular guzzle a lot of water - watering lawns would have to be fully prohibited before anyone sensible started rationing drinking water, as the latter is a public health issue, and lawns are merely pretty. Having restaurants limit water is pure theatre, as bradleyjg has already mentioned.