As suggested by
@metalinvader665 I created a thread explictly for this.
One of the peak moments (IMO) for Nubia was the 25th Dynasty and its brief rule over Egypt.
Ignoring the repercussions (or at least the non-immediate ones for now), what would it require for them (instead of building Nubian Pyramids), they decided to invest the time and energy to circumvent the various Cataracts around the Nubian Swell. Perhaps to justify it to themselves, it is to make transport between Nubia and Upper Egypt smoother - and make the Empire more secure as a result.
It has been mentioned before (including by
@DominusNovus ) that the most practical canal (i.e. one that cuts across the longer stretches of river), requires locks and other complexities to raise and lower the water.
In contrast, I think that the best option (technologically, not in terms of ideal project), would be to run parallel to the river, entirely designed to circumvent those parts of the Cataracts that aren't navigable.
The problem with that is determining the exact distances involved, and whilst some Cataracts will be relatively short, and as such the length of the canal needed is shorter - I don't expect that to be universally the case.
Overall I guess I'm asking for information on the practicalities of such a project, working within the limitations of Nile Valley Stoneworking.
On top of that, which stretches do you circumvent first? The most upriver cataracts make travel in Nubia easier, all the way down to the Sudd (which has its own advantages), but the lowermost cataracts open up stretches of the Cataract Nile to the Egyptian Nile.
I am under no misunderstanding that it is a massive project. (I mean, it hasn't been attempted IOTL), but I want to at least discuss the practicalities, before starting a thread on the impacts (tempting it may be).