Sure Shot, about half a mile. Normally the river is higher, and the dog would not have been able to cross over. (Edit: he's a she, by the way, named "Lola". Big baby, loves kids, particularly infants and toddlers. With the wife pregnant, we were really upset about that aspect.)
That said, as noted, the wife is now on board with not letting the dog run; my first project when I get home is installing invisible fence around the yard, and later extending it around the pastures.