[mekoka]

As it certainly doesn't need to be proven further, Egyptians were quite an ingenious people. All of the things you're suggesting as obstacles would probably be trivial to deal with for them at their advancement level. A commenter (seferphier) posted this link that may provide a glimpse into additional possible cues, I suggest to have a look http://www.youtube.com/watch?v=C1y8N0ePuF8&feature=youtu.be&.... I particularly liked the part where it is suggested that it would be relatively easy for them to move 600 litres of water in a single minute. With virtually unlimited water and such a capacity to move it, I think the theory might be plausible and merits further investigation.