Mmm, I remember back in a drought of the early 80's when there was a hosepipe ban in force where we are my dad opened up an old well on our property and used water from there to water his garden. Someone reported him as they thought he was flouting the hosepipe ban, the water company came round and checked and told him he was fine and perfectly at liberty to use the water in his own well to water his garden.
However, this was over 25 years ago and in Scotland (and I suppose Scots Law may be different anyway).