A river in Africa that overflows its banks in summer, and along which a plant grows, from the stem of which ancient paper was made?

We are talking about the longest (6671 km) river in Africa, the Nile. It does not dry up, despite the heat, thanks to the abundant equatorial rains that come at its source.
From papyrus, a relative of our reeds, growing along the banks of the Nile, the ancient Egyptians made not only the first paper, but also household items – mats, baskets, etc.