While cycling through Africa, I took a break from the bike and spent 2 weeks paddling down the upper reaches of the Niger River in Guinea - 350km from Faranah to Kouroussa. This was using a locally made wooden boat, but could certainly be done by packraft… and in fact, would be better suited I think.
We left quite late into the dry season and so parts were v shallow or with rocks lying close to the surface - it was hard work dragging the heavy boat, whereas a packraft would not have had the same problems!
It was an amazing experience and I would highly recommend it.
Anyway, there’s a short film I made about the trip if anyone’s interested: http://helenstakeon.com/africa/video-of-the-great-niger-river-boat-trip/