The USGS Water Science School
If you ever wondered if the expression "Water makes the desert bloom" was true, there is no better proof than this satellite picture by NASA of the Nile Valley in Egypt. For thousands of years, the lower Nile valley (northern end) has been a cradle of civilization. Surrounded by deserts, the Nile river brings much-needed water to the land and people, making the valley into an oasis of agriculture and life.
In this picture the Nile River runs north to the edge of the Mediterranean Sea, where it widens out into a vast delta. Just at the apex of the delta is the ancient city of Cairo. The city appears as a gray spot sandwiched between the delta and the northern end of the Eastern Desert. The leaf-shaped patch of green branching off of the left (western) side of the Nile Valley is a depression in the Libyan Desert that has been used as an irrigated agricultural area since 1800 BC, when the original irrigation canals were dug. The depression is fertilized by the Nile's water and silt.
Credit: Jeff Schmaltz, NASA Visible Earth