Nile river boat

Recycling doesn't always make sense. It is easier to fashion a new piece of wood than to carry one 600 miles. On many rivers, most of the hull didn't return. Some choice, high-value items might make the trip back upstream, but the rest was quite valuable as a raw material in the denuded desert. And remember, they still had to transport the darn thing across the desert once they got it down the river. So there was probably a large portion of multi-modal components.

 

I can't help wondering what the riverbed topology was a couple thousand years ago. I notice on the map that the first cataract is at Aswan, and I'm pretty sure they didn't have a dam there back then.

 

So 3.5Ky BP is ~1500 BCE.

 

Ancient Egyptian used a device called a shaduf, for irrigation.

It is the foundation design, of Archimedes' crane

I suspect, that with all the counterbalance resources a dessert can provide, getting the blocks on and off a barge wasn't that difficult.

Also, gin poles have been around for a long long time.

 

that, plus lots of rivers will have slow upriver currents along the banks. Lewis & Clark used that often. You can see it several spots on Stanislaus River run from Knight's Ferry. You can see scum and leaves on top of the water moving upstream where the river gets wide.

 

rivers are shallow and move very slowly or even upstream, on the inside of bends, and fast and deep on the outside curves.

Note the beach on the inside curve, where sediment can settle, and the outside bank gets undercut.

Unladen shoal draft barges to the inside, going upstream, deeper, loaded vessels on the outside, going down stream.