I think if you look closely you can see the barest edge of a bucket behind the central part of the structure, where they'd drain the actual initial liquid. (You can see that the fluid seems to arrest before that transition in the video, as well.)
and he edited the video so that the fluid flow looks smooth when the water reaches to upper most brigde. look closely at 0:43 there is something strange happening to the fluid flow. but alas great work!!
http://imgur.com/EMUJL
I think if you look closely you can see the barest edge of a bucket behind the central part of the structure, where they'd drain the actual initial liquid. (You can see that the fluid seems to arrest before that transition in the video, as well.)