Eventually, as the water flows through this area, large amounts of vegetation are dislodged and carried downstream where they fill the channels and prevent navigation. The basin in this area also receives drainage from other rivers and streams. Some of the contributors lose tremendous amounts of water from evaporation and only a small amount of water is added to the Nile. It continues for about 500 miles with very little water being added from other sources along the way. This section of the Nile is wide and the water flows slowly along its course.
Narrow swamps occur frequently along the edges.
These conditions contribute to the massive amounts of water lost through evaporation and seepage. The water of the Blue Nile drains from the Ethiopian Plateau, where it descends from 6,000 feet above sea level. It continues in a north-northwesterly direction through The Sudan until it reaches the White Nile at Khartoum, shown in this picture. The White Nile has a relatively constant flow. The Blue Nile in contrast is affected by the tremendous runoff resulting from the late July to October rains on the Ethiopian Plateau.