From this column here:
This silly practice [of putting jugs of water on a lawn to deter dogs] has been floating around since the late 1970s, and by now has spread all over the world. Folklorist Jan Brunvand, who tells the whole story in his book, Curses! Broiled Again!, says he saw plastic bottles on lawns everywhere during a trip to New Zealand, and apparently they were common in Australia, too.
I was born in New Zealand in 1981 and lived there until 2000, and I certainly don’t remember anyone putting jugs of water on the lawn to act as a dog deterrent.
Then again, everyone’s house tended to have fences on the lawn, and I don’t recall that many dogs running around in the street unleashed in the city I lived in (Dogs off leashes in rural areas were considered target practice for farmers, incidentally).
I’d be interested to see where all these Jugs were seen- it may have been an Auckland thing that didn’t spread south, or perhaps I just wrote it off with all the other generally odd stuff that happens in NZ…