Remember Streams can flow underground as well as overground, maybe it's a question for dowsers, i'm pretty sure i remember reading or being told by dowsers that the Avenues at Avebury follow underground watercourses, i'm not so sure myself but the kink in the WKA near Avebury is very watercourse like, and would explain why you think there may be a link between the Avenues and Water, Just a thought...