Interesting - in this article it says that the ditch hadn't been opened up yet, until Tuesday. So it would have been dry before then, when the area had been searched before.
So I'm wondering, literally, where could it have come from? Usually there are "gates" along the ditches, where anything large couldn't get through. I just don't know where these are located.
Whoops posted the same quesion! Yes, I am wondering the same thing. I don't see a grate on the pipe portion and the gate at the top of the ditch east had to have been open as she was found at the bottom.