Stormwater is also a resource and important as the world's human population demand exceeds the availability of readily available water. Techniques of storm water harvesting with point source water management and purification can potentially make urban environments self-sustaining in terms of water.
Rivers flow downhill to sea level (generally speaking; some end in other bodies of water or join another rver). They flow with gravity from a higher elevation to a lower. The Nile rises on the western flank of the Great Rift Valley (many people consider Lake Victoria to be the source) and the Blue Nile joins the White Nile at Khartoum. The land falls away towards the north, thus the river flows north until it reaches the Mediterranean Sea at the Nile Delta. Direction of flow of a river is determined by elevation of the drainage basin, not geographical (North, South etc.) direction. http://en.wikipedia.org/wiki/Nile#Course.
The source of the Nile is sometimes considered to be Lake Victoria, but the lake itself has feeder rivers of considerable size like the Kagera River. Interesting Facts about the Nile river: 1  The Nile River is the longest river in the world. 2  The Nile flows into the Mediterranean Sea. 3  The Nile has a length of about 6,695 kilometers (4,160 miles). 4  Its average discharge is 3.1 million litres (680,000 gallons) per second.