The longest river in the world, the Nile flows
4,184 miles (6,695 km) from its remotest headwater stream,
the Luvironza River in central Africa’s Burundi, to its delta
on the Mediterranean coast. The Nile drains more than
1,100,000 square miles (2,850,000 km2) amounting to 10
percent of Africa, including parts of Egypt, Sudan, Ethiopia,
Uganda, Kenya, Rwanda, Burundi, and Zaire. Water from
the Nile is used for almost all of the irrigation and agriculture
in Egypt and about 20 percent of the irrigation in Sudan. The
river is widely used for transportation, hydroelectric power,
and as a source of food.
The Nile has two main tributaries, the White Nile and the
Blue Nile, that meet in Khartoum, Sudan, then flow together
to the north to the sea. Lake Victoria in Uganda is the main
headwater reservoir for the White Nile, whereas Lake Tana in
Ethiopia is the main headwater reservoir for the Blue Nile. The
White Nile flows north out of Lake Victoria over Owen Falls
into the Victoria Nile that flows into Lake Albert on the floor
of the East African rift system and then is known as the Albert
Nile as it flows north out of Uganda. This region receives high
rainfall all year round, so the flow of water in the White Nile
is close to constant. In southern Sudan the river becomes
known as the Mountain Nile, before it makes a bend to the
east and is joined by the Bahr al-Ghazal River and it turns
back to the north as the White Nile. This relatively straight
stretch continues to Khartoum where the White Nile is joined
by the waters of the Blue Nile. The Blue Nile begins its journey
on the northern slope of the Ethiopian highlands, formed by
uplift and volcanism on the Ethiopian dome around the Afar
triple junction. This region receives heavy summer rains, and
these are the source of the floodwaters that reach Egypt nearly
every September. The Blue Nile and its many tributaries flow
over rugged volcanic terrane into Sudan, where a reservoir has
been created by damming Lake al-Azraq. The Blue Nile then
meanders across southern Sudan until it meets the White Nile
at Khartoum. More than half of the Nile’s water is contributed
by the Blue Nile, and during flood season, most of the silt in
the river comes from erosion of the Ethiopian highlands. From
Khartoum, the merged White and Blue Niles form a new trunk
stream, that flows in a narrow channel with virtually no floodplain
around a great bend where the waters flow first northeast,
then swing northwest, and then southwest before
continuing to the north. Old river channels followed a more
direct route through the Bayuda Desert region the river now
flows around, so it is evident that the Bayuda Desert region is
experiencing active uplift that has deflected the river to the
east. From Khartoum to the Egyptian border, the river must
flow over six sections containing rapids, known locally as
cataracts. As the river flows out of Sudan it enters Lake Nasser
in Egypt, created by construction of the Aswan High Dam.
The Nile then continues north through Upper Egypt, past
Assuit and Cairo, and splits into tributaries in the delta region
before flowing into the Mediterranean Sea. The floodplain of
the river broadens in Egypt, first to around 10 miles (16 km)
south of Cairo, then broadens dramatically to more than 100
(160 km) miles wide on the delta north of Cairo. The delta is
the main agricultural region of Egypt, containing more than 60
percent of the cultivated lands in the country.
In Sudan, the region between the White Nile and Blue
Nile is known as Al-Jazirah (or Gezira), meaning the island.
This region is extremely fertile and serves as the principal
agricultural area in Sudan, and it is the only large area outside
Egypt where Nile waters are used extensively for irrigation.
The Egyptian government is currently attempting a massive
project to form a second arm of the Nile extending out
of Lake Nasser and flowing across the Western Desert to
eventually reach the sea near Alexandria. This ambitious project
starts in the Tushka Canal area, where water is drained
from Lake Nasser and steered into a topographic depression
that winds its way north through some of the hottest, driest
desert landscape on Earth. The government plans to move
thousands of farmers and industrialists from the familiar Nile
Valley into this national frontier, hoping to alleviate overcrowding.
Cairo’s population of 13 million is increasing at a
rate of nearly one million per year. If successful, this plan
could reduce the water demands on the limited resources of
the river. However, there are many obstacles with this plan.
Will people stay in a desert where temperatures regularly
exceed 120°F (49°C)? Will the water make it to Alexandria,
having to flow through unsaturated sands, and through a
region where the evaporation rate is 200 times greater than
the precipitation rate? How will drifting sands and blowing
dust affect plans for agriculture in the Western Desert? Much
of the downriver part of the Nile is suffering from lower
water and silt levels than are needed to sustain agriculture
and even the current land surface. So much water is used,
diverted, or dammed upstream that parts of the Nile Delta
have actually started to subside (sink) beneath sea level.
These regions desperately need to receive the annual silt layer
from the flooding Nile to rebuild the land surface and keep it
from disappearing beneath the sea.
There are also political problems with establishing the
New River through the Western Desert. Ethiopia contributes
about 85 percent of the water to the Nile, yet it is experiencing
severe drought and famine in the eastern part of the country.
There is no infrastructure to get the water from the Nile
to the thirsty lands and people to the east. Sudan and Egypt
have long-standing disputes over water allotments, and
Sudan is not happy that Egypt plans to establish a new river
that will further their use of the water. Water is currently
flowing out of Lake Nasser, filling up several small lake
depressions to the west, and evaporating between the sands.
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