Aaaah! I knew that rivers worked as if they were roads in some case(s) but didn't remember which of them it was.No, in Civ 2 and Civ 2 ToT trade workes different from Civ 3 as there are no strategic and luxury resources but caravans. Exploring along rivers in Civ 2 gives a movement bonus like a road.
Still, using rivers as tradeways (again, look at OpenTTD) might be a useful thought.