I'm with Ethiopia on this one, why does Egypt think the nile is theirs?
Several dozens of Egyptian cities and millions of Egyptians depend on the Nile. Now think about how East Africa has been ravaged by famines and droughts, and in the future Egypt is going to be one of the countries hit the hardest by climate change + water is predicted to become the main reason for war/conflict in the future.
The Nile is their life source, if they believe Ethiopia is going to constraint it, they will act militarily.
In Pakistan, most of the people depend on the Hindus river. It's their main source of water, irrigation and much more. Yet it originates in India, and these two countries have a treaty saying India can't touch it.
Still, due to dodgy relationship, Pakistan has threatened military and nuclear retaliation if India decides to f*ck around with the river.