Geographic Setting, Hydraulic Civilization on the Nile


The Nile in Geographic Context
		LAST UPDATE: 10-25-2012

Although at its height, the Egyptian Kingdom extended southward to the confluence of the Blue Nile and the White Nile (left), its heartland always consisted of the entrenched floodplain, delta and Fayum Basin, highlighted above in green. It is technological, economic, social and religious innovations in this region that allowed the kingdom to grow and flourish for three millennia.
This section of the course is intended to place this region into its broader geographic and environmental context.

Water Vapor in Earth's atmosphere that was available for precipitation in May, 2009. Blue is less; Red is more. The page header image is another such image with a bit more detail. Note just how dry Egypt appears from on high. Water vapor, of course, is only part of the story. You must also have the conditions necessary to condense the vapor and cause it to precipitate.

This image was prepared in order to map the probability of prolonged drought in the near future, but id does an excellent job of reflecting the distribution of rainfall, desert and non-desert. Notice that the kingdom of ancient Egypt falls entirely within the deserts and arid steppes of north Africa.

Based on satellite data, this image depicts world precipitation during 2009. This is the dance that determines the timing of the Nile floods. Notice how the Ethiopian Highlands, source of the Blue Nile, benefits from both the northern winter rainfall system and the southern tropical rainfall system. Note, too, how Egypt receives little direct benefit from either.

Surface water at the wettest time of the year, showing what streams and rivers are flowing. It is rain falling in July and August that feeds the Nile when it is in flood in September. Based on data sets in the Digital Chart of the World. Look at the animated figure above this one to see the pattern of precipitation that creates this distribution of surface water.

Surface water at the dryest time of the year, in January, showing what streams and rivers flow all the time. This condition is not fully expressed on the lower course of the Nile until April. The blue in the Faiyum and the Nile Delta reflect irrigation. Based on data sets in the Digital Chart of the World. Look at the animated figure (2nd above) to see the pattern of precipitation that creates this distribution of surface water.

Profiles Nile River and its major tributaries.

Major contributions to the flow of the Nile River. From Nine Nations, One Nile, by Jullie M. Smith, 1999, Figure 6 [from Population-Environment Dynamics: Ten Case Studies, University of Michigan.

Profiles of the Blue Nile and the White Nile. Note the extreme vertical exaggeration. The distance from the ocean to the first cataract is about 675 miles; from the ocean to Khartoum about 1,875 miles. On average the floodplain between Aswan and the head of the Nile Delta descends about 30 inches in every 100 yards, which is ideal for floodplain and irrigation agriculture. From Nine Nations, One Nile, by Jullie M. Smith, 1999, Figure 5 [from Population-Environment Dynamics: Ten Case Studies, University of Michigan.

This is the first cataract at Aswan. We are just south of the head of the cataract looking north where the Nile is suddenly blocked by a series of resistant rocks, causing the river to divide into a number of shallow reaches. A series of these cataracts prevent the river from deeply incising its valley and promote the development of the agriculturally fertile floodplain necessary for the development of ancient civilization in the Nile Valley.

The narrow channels of the First Cataract, at Aswan, can be navigated by small vessels with with only a little draft, but large vessels can't easily pass even at high water. A number of the other cataracts are even more difficult to navigate.

The hatched region that contains many units of very hard rock, such as granite. Where thee units run beneath the Nile River, they form "cataracts" that make erosion very difficult and cause sediment to be retained on the upstream side. They also cause the river to meander, which widens the valley, creating and sustaining a broader floodplain. Without such formations, the Nile would incise a deeper, narrower valley with less agricultural potential.

The Nile delivers enormous amounts of sediment to the sea, forming a vast delta, most of which is actually underwater. The area not underwater is about 25,000 square km. (about 9,600 square mi. or the size of Vermont), most of which is in continuous agricultural production.