[Spooky23]

Very simple. Now scale it to feed an army with 2000 year old technology.

[andrewflnr]

Ok, but remember, in this benighted subthread, we're comparing with a proposal to move seawater instead, in equivalent amounts.

[thaumasiotes]

I can't tell what you think you're saying. Not only was this done routinely, it was much easier than the more obvious problem of providing the army with grain.