The Nile Border in Future Israel

[edu]

At http://en.wikipedia.org/wiki/Nile you will find various maps of the Nile river
I am linking to one of them

My question is: When G-d promises Avraham that his seed will receive the territory from the Nile to the Euphrates, what part of the Nile is the future border? Is it only the Northern edge of the river or is it all along the Nile River deep into Africa? Or something in the middle?

[muman613]

Shalom Edu,

Haven't you ever seen this map?

[edu]

Interested to know Muman613 what Rabbinic support you have for the map you brought?

Recently, I saw a book by Rabbi Yisrael Ariel, who seems to make the north right tip of the Nile as the future border. But even Rabbi Ariel claims that the entire Sinai will belong to Israel, even though part of the Sinai region is below (that is to say to the south of) the north right tip of the Nile.
I have not yet read his book in depth to see if he explains why we shouldn't draw a straight line from the edge of Sinai to the Middle of the Nile River.
A further issue that needs clarification is that at first glance it appears that the future land of Israel has a roughly square appearance, because it appears from the Talmud Megilla 3a and Baba Kama 82b and Menachot 62b, that the land of Israel is 400 Parsa by 400 Parsa.
Rabbi Ariel's borders have more of a triangular appearance.
I am not presenting here final conclusions, I'm just hoping to move along the discussion.