I was in the Oasis in Act 2 where you get Krull's head. I do not know the correct name and am not infront of the game (otherwise id be playing and not caring about posting here). Anyways I got his head and then it said go back to town talk to adria. Did that then the next part of the quest was to go to the Aquaducts back in the Oasis. Only problem is i explored the whole Oasis already and there were no Aquaduct entrence. I do not know if this is a bug or simply a random environment side effect, but I had to leave the game and reenter to have them spawn right where they should have been.

Hope this helps.