I think they used temporary canals, probably when the Nile river flooded annually, from melting snow. Keep in mind that the Nile is one of the few rivers in the world that flows from South to North. The annual flood left a LOT of soil near the banks of the river, on either side, so it wasn't ALL desert; only east and west of the flood plain. The Pyramids are in the north, near the Delta, (the area where the river splits into many smaller streams, with swampy marshes in between them, because the river no longer flows downhill, at that point.
It would be a lot easier to move those large blocks of rock if they were on rafts. They could move them above the target location, then let water out, to drop them in place. It's like lying down in a full bathtub, then letting water out, to try to land the rubber ducky on your junk.