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Major river in northeastern Africa For other uses, see Nile (disambiguation).

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Nile River
The Nile downstream from Murchison Falls
Location
Countries	Burundi, DR Congo, Egypt, Eritrea, Ethiopia, Kenya, Rwanda, South Sudan, Sudan, Tanzania, Uganda[1]
Major cities	Bahir Dar, Cairo, Khartoum, Jinja, Juba
Physical characteristics
Source	Rukarara River, Rwanda[2][a]
• coordinates	02°19′35″S 29°21′30″E / 2.32639°S 29.35833°E / -2.32639; 29.35833[2]
• elevation	2,539 m (8,330 ft)[2]
Length	7,088 km (4,404 mi)[3]
Basin size	2,927,843 km2 (1,130,447 mi2)[1]
Discharge
• location	Nile Delta into Mediterranean Sea
• average	150 m3/s (5,300 cu ft/s)[4]

The Nile[b] (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa and flows into the Mediterranean Sea. At 7,088 km (4,404 mi) long, it is the longest river in the world, although the volume of water it carries is much smaller than other major rivers such as the Amazon or Congo. Its drainage basin covers eleven countries: the Democratic Republic of the Congo, Tanzania, Burundi, Rwanda, Uganda, Kenya, Ethiopia, Eritrea, South Sudan, Sudan, and Egypt. It plays an important economic role in the economy of these nations, and it is the primary water source for South Sudan, Sudan and Egypt.

The Nile has two major tributaries: the White Nile and the Blue Nile. The White Nile, being the longer, is traditionally considered to be the headwaters, while the Blue Nile actually contributes 80% of the water and silt below the confluence of the two. The White Nile begins at Lake Victoria and flows through Uganda and South Sudan, while the Blue Nile begins at Lake Tana in Ethiopia[7] and flows into Sudan from the southeast. The two rivers meet at the Sudanese capital of Khartoum.

After Khartoum the river flows north, almost entirely through the Nubian Desert, to Cairo and its large delta, joining the Mediterranean Sea at Alexandria. Egyptian civilization and Sudanese kingdoms have depended on the river and its annual flooding since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of the Aswan Dam. Nearly all the cultural and historical sites of Ancient Egypt developed and are found along river banks. The Nile is, with the Rhône and Po, one of the three Mediterranean rivers with the largest water discharge.

Etymology

The word Nile is derived from the from the Latin Nilus and the Ancient Greek Νεῖλος (Neilos), which probably originated from the Semitic term naḥal, meaning "river".[8] In the ancient Egyptian language, the Nile was called Ar or Aur, meaning "black".[8] In Coptic, it was called ⲫⲓⲁⲣⲟ.[8]

Physical geography

Sources

The source of the Nile is a tributary of the Rukarara River, in Nyungwe National Park, Rwanda, at 2°19′35″S 29°21′30″E / 2.32639°S 29.35833°E / -2.32639; 29.35833, at an elevation of 2,539 meters.[2][a] The source is defined as the starting point of the longest year-round watercourse in the Nile's drainage basin.[3] From this source, the river runs 7,088 km to the river's mouth at the Mediterranean Sea.[3] The distance was determined from satellite imagery, and was measured along the centerline of the river.[3]

The highest sources of the Nile (based on elevation) are on the eastern slopes of the Rwenzori Mountains in Uganda.[10][c] The legendary Mountains of the Moon, described by Ptolemy, have been associated with Rwenzori.[10]

The southernmost source of the Nile is in Burundi at one of the heads of the Ruvyironza River, which feeds into the Kagera River. A monumuent was erected there in 1937 by Burkhart Waldecker near the town of Rutovu, close to Mount Kikizi.[12][d]

Lake Victoria is sometimes informally described as the source of the Nile, partly because early European explorers claimed that the lake was the source; and partly because the lake's outflow river is the most upstream river called the "Nile" (rivers flowing into Lake Victoria, such as the Kagera River, do not have the word "Nile" in their names).[13]

The source of the Blue Nile tributary is near the town of Gish Abay, south of Lake Tana.[14][e]

Regions of the Nile Basin

The Nile Basin can be divided into seven regions; five of these regions encompass the longest course of the Nile River. Proceeding in a downstream sequence, these five regions are: the African Great Lakes, the Mountain Nile, the White Nile, the main Nile, and the Nile Delta. Two additional regions encompass major tributaries: the Blue Nile and the Atbarah River.[8]

The region Africa around its Great Lakes contains the source of the Nile river. The source is the Rukarara River within Rwanda's Nyungwe National Park,[3] and it leads to the Kagera River,[f] which drains into Lake Victoria.[8] Although it is a large lake – the second-largest freshwater lake in the world[g] – Lake Victoria is relatively shallow. The Nile river first assumes the name "Nile" where Lake Victoria empties on its north side: the course from there to Lake Albert is called the Victoria Nile.[8] A pair of waterfalls – Ripon Falls and Owen Falls – were located where the Nile exits Lake Victoria, but have both been submerged by the construction of the Nalubaale dam. After Bujagali Falls and Bujagali Power Station, the Victoria Nile empties into Lake Kyoga. After exiting Lake Kyoga, the river is joined by the River Kafu tributary, then passes over Murchison Falls and flows into Lake Albert. Unlike Lake Victoria, Lake Albert is a deep lake surrounded by mountains. The river exits Lake Albert on its north shore, where it is called the Albert Nile; this stretch of the river is relatively flat and broad, and suitable for navigation by steamboats.[8]

The second region of the Nile Basin, proceeding downstream, is the Mountain Nile (in Arabic: Bahr al Jabal).[15] This region begins near the town of Nimule and extends to Lake No, and is entirely within South Sudan. After passing through Nimule, the river goes through the Fula Rapids and on to Juba – the capital city of South Sudan. After Juba, the Nile passes through the town of Bor, then enters the Suud, a large swamp located in a flat plain. The slope of the ground in the Sudd is only 1:13,000, so the river slows down and widens. Lush vegetation, including sedges, papyrus, and common water hyacinth (an invasive species) clog the waterways and make navigation difficult. At the downstream edge of the Sudd swamp, the Nile is joined by the Bahr el Ghazal River (Arabic: "gazelle river") a tribuatary flowing from the west. This confluence happens in Lake No.[8]

Continuing downstream, the third region of the Nile Basin is the White Nile region.[h] About 140 km after Lake No, the swamps diminish near the city of Malakal, and the river enters a long, placid stretch extending to Khartoum, where it is joined by the Blue Nile near Khartoum, the capital of Sudan.[8]

The fourth region of the Nile Basin – the main Nile[i] – extends from Khartoum to Cairo, the capital of Egypt. Soon after leaving Khartoum, the river goes enters the Sabloka Nature Reserve[j] and goes through the sixth (and furthest upstream) of the renowned six cataracts of the Nile. The Atbarah River – a major tributary – joins the Nile, which then follows a large S-shape curve to the west. Four more cataracts are encountered in this large S-curve, which render the river unnavigable, although ships may travel between the cataracts. The river then enters a large reservoir, Lake Nasser.[k] This lake – the world's second largest man-made lake – was formed when the Aswan High Dam was built in Egypt, and inundates more than 480 km of the Nile river. A second dam, older and smaller, lies beneath the Aswan High Dam, near the location of the first Nile cataract (now submerged). From these dams, the Nile flows about 800 km through a limestone plateau, bordered by large amounts of irrigated farmland, until it reaches Cairo.[8]

The fifth, and final, region encompassing the Nile river is the Nile Delta, a large triangular river delta that extends from Cairo to the Mediterranean Sea.[8] The river splits into two major distributaries (channels) within the delta: the Rosetta branch and the Damietta branch. The soil in the delta, ranging from 15 to 22 meters thick, was built-up over millennia from silt carried by the river from far upstream, in the Ethiopian highlands.[8]

The final two regions of the Nile Basin are the Blue Nile basin and the Atbarah River basin,[8] both discussed in the section on Tributaries.

Tributaries

The longest course of the Nile, which includes the White Nile tributary, has several other tributaries that feed into it.

Blue Nile

Main article: Blue Nile

The Blue Nile springs from hills in the Ethiopian Highland[14] where it originates as a stream named Abay near the town of Gish Abay:Gish in an Amharic word meaning 'source', and Abay is the name of the stream.[14][17] Gish Abay flows into Lake Tana, a large, shallow lake, which has a single outflow where it adopts the 'Blue Nile' name. The Blue Nile travels south, then north passing through South Sudan into Sudan, where it joins with the White Nile at Khartoum to form the main Nile.[17] Along its course, the Blue Nile generates electricity at several hydro power plants, including the Tisabay hydropower project at the Blue Nile Falls, the Grand Ethiopian Renaissance Dam near the border between Ethiopia and South Sudan, the Roseires Dam near town of Ad Damazin, and the Sennar Dam.[18] The size of the Blue Nile's drainage basin is over 306,000 square km.[19]

Atbarah River

Main article: Atbarah River

The Atbarah River is a tributary of the Nile which arises in northern Ethiopia, and joins the Nile about 320 km north of Khartoum.[20] Its drainage basin covers over 204,000 square km.[19] The Atbarah has a heavy flow during and following the monsoon season in Ethiopia (summer and fall), but can dry up in the winter and spring. Despite the intermittent nature of the river, it provides more than 10% of the total annual flow of the Nile.[20] Dams on the Atbarah include the Khashm el-Girba Dam, the Upper Atbara and Setit Dam Complex, and the Tekezé Dam (on the Tekezé River tributary).[21]

Bahr el Ghazal and Sobat River

The Bahr al Ghazal and the Sobat River are two tributaries of the White Nile. The Bahr el Ghazal arrives from the west, joining the White Nile at Lake No. The drainage basin of the Bahr el Ghazal river is large – about 860,000 square km[22] – and receives a relatively large amount of rain, but its contribution to the Nile is insignificant.[l] The basin includes Lake Kundi and Lake Keilak. The Bahr el Ghazal passes through the city of Wau, South Sudan: it is a permanent stream east of Wau, but a seasonal stream to the west.[24]

Another tributary, the Sobat River, joins the White Nile (after the Bahr el Ghazal confluence, before the Blue Nile) near the town of Malaka. Its basin – which includes the Machar Marshes[25] – covers about 225,000 square km.[26] The Sobat floods between July and December.[8]

Hydrography

Flow and floods

The flow rate of the Bahr al Jabal at Mongalla is almost constant throughout the year and averages 1,048 m3/s (37,000 cu ft/s). After Mongalla, the Bahr Al Jabal enters the enormous swamps of the Sudd region. More than half of the Nile's water is lost in this swamp to evaporation and transpiration. The average flow rate of the White Nile at the tails of the swamps is about 510 m3/s (18,000 cu ft/s). From here it meets with the Sobat River at Malakal. On an annual basis, the White Nile upstream of Malakal contributes about 15% of the total outflow of the Nile.[27]

The average flow of the White Nile at Lake Kawaki Malakal, just below the Sobat River, is 924 m3/s (32,600 cu ft/s); the peak flow is approximately 1,218 m3/s (43,000 cu ft/s) in October and minimum flow is about 609 m3/s (21,500 cu ft/s) in April. This fluctuation is caused by the substantial variation in the flow of the Sobat, which has a minimum flow of about 99 m3/s (3,500 cu ft/s) in March and a peak flow of over 680 m3/s (24,000 cu ft/s) in October.[28] During the dry season (January to June) the White Nile contributes between 70% and 90% of the total discharge from the Nile.[citation needed]

Ninety percent of the water and ninety-six percent of the transported sediment carried by the Nile[29] come from the Atbarah and Blue Nile, both of which originate in Ethiopia, with fifty-nine percent of the water coming from the Blue Nile. The erosion and transportation of silt only occurs during the Ethiopian rainy season when rainfall is especially high in the Ethiopian Highlands; the rest of the year, the great rivers draining Ethiopia into the Nile have a weaker flow. In harsh and arid seasons and droughts, the Blue Nile dries out completely.[30]

The flow of the Blue Nile varies considerably over its yearly cycle and is the main contribution to the large natural variation of the Nile flow. During the dry season the natural discharge of the Blue Nile can be as low as 113 m3/s (4,000 cu ft/s), although upstream dams regulate the flow of the river. During the wet season, the peak flow of the Blue Nile often exceeds 5,663 m3/s (200,000 cu ft/s) in late August (a difference of a factor of 50).[citation needed] Before the placement of dams on the river the yearly discharge varied by a factor of 15 at Aswan. Peak flows of over 8,212 m3/s (290,000 cu ft/s) occurred during late August and early September, and minimum flows of about 552 m3/s (19,500 cu ft/s) occurred during late April and early May.[citation needed]

Hydrology data

The following tables summarize the hydrology of the Nile Basin. The data is based on measurements made at twelve river measurement stations.[31] The stations divide the basin into twelve basins. These basins are each named after their downstream station. For example, the Murchison Falls station (2) is downstream of the Lake Victoria outlet station (1), so the basin between them is named the Murchison Falls basin.[32] The data includes the following:

Per-basin data: land surface area, precipitation, evapotranspiration, surface runoff
Per-station data: discharge

Most of the per-basin data is presented as annual measurements (usually in km3); but some data is also presented as an equivalent "depth" value (millimeters per year, covering the entire basin).[31]

Basin data

The water balance datum of each basin is a rudimentary calculation of precipitation−evapotranspiration.[33] Each basin is classified as a source, sink, or neutral, indicating if it is a net contributor to the river's flow (source) or if the adjusted evapotranspiration significantly exceeds precipitation (sink).[34]

The measuring stations are listed in the tables proceeding from upstream to downstream.

White Nile tributary hydrology (annual)[35]

MeasuringStation	BasinArea km2	Precip km3 (depth)	Evap km3(depth)	WaterBalance km3	Runoff km3 (depth)	Discharge km3 (rate)	Source? (No=sink)
1 Lake Victoria outlet[m]	264,259	353 (1,337 mm)	279 (1,055 mm)	74	57 (214 mm)	37 (1,176 m3/sec)	Yes
2 Murchison Falls[n]	85,513	109 (1,276 mm)	94 (1,105 mm)	15	9 (102 mm)	30 (946 m3/sec)	Yes
3 Mongalla[o]	131,691	159 (1,209 mm)	158 (1,201 mm)	1	5 (38 mm)	33 (1,050 m3/sec)	Neutral
4 Malakal[p]	925,160	798 (863 mm)	957 (1,034 mm)	−159	150 (162 mm)	30 (939 m3/sec)	No
5 Khartoum[q]	257,130	134 (520 mm)	174 (676 mm)	105	14(53 mm)	28 (897 m3/sec)	No

Blue Nile tributary hydrology (annual)[35]

MeasuringStation	BasinArea km2	Precip km3 (depth)	Evap km3(depth)	WaterBalance km3	Runoff km3 (depth)	Discharge km3 (rate)	Source? (No=sink)
6 Roseires Dam[36]	188,296	246(1,309 mm)	142 (752 mm)	105	70 (372 mm)	49 (1,548 m3/sec)	Yes
7 Khartoum [r]	118,651	96 (686 mm)	72 (605 mm)	10	9 (75 mm)	48 (1,513 m3/sec)	Neutral

Atbarah tributary hydrology (annual)[35]

MeasuringStation	BasinArea km2	Precip km3 (depth)	Evap km3(depth)	WaterBalance km3	Runoff km3 (depth)	Discharge km3 (rate)	Source? (No=sink)
8 Khashm el Girba[s]	100,318	95 (951 mm)	66 (656 mm)	30	10 (104 mm)	10 (302 m3/sec)	Yes
9 Mouth of Atbarah River[t]	104,051	22 (215 mm)	25 (242 mm)	−3	1 (6 mm)	12 (373 m3/sec)	Neutral

Main Nile hydrology (annual)[35]

MeasuringStation	BasinArea km2	Precip km3 (depth)	Evap km3(depth)	WaterBalance km3	Runoff km3 (depth)	Discharge km3 (rate)	Source? (No=sink)
10 Dongola[36]	390,180	34 (87 mm)	45 (116 mm)	−11	0 (0 mm)	83(2,622 m3/sec)	Neutral
11 Aswan dam[36]	188,011	2 (12 mm)	13 (70 mm)	−10	0 (0 mm)	87 (2,757 m3/sec)	No
12 Cairo/Delta[u]	145,293	3 (18 mm)	12(85 mm)	−10	0 (0 mm)	40 (1,251 m3/sec)	No

Country data

This table contains hydrology data for the Nile Basin, on a per-country basis. Portions of countries outside the Nile Basin are excluded from the values.

Country hydrology (annual)[1]

Country	BasinArea km2[v]	Precip km3 (depth)	Evap km3(depth)	WaterBalance km3	Runoff km3 (depth)
Burundi	13,240	14 (1,092 mm)	13 (951 mm)	2	3(242mm)
DR Congo	19,919	96 (686 mm)	72 (605 mm)	10	9 (75 mm)
Egypt	235,108	4 (1,092 mm)	13 (951 mm)	39	0 (0mm)
Eritrea	24,427	14 ( 572 mm)	12(507 mm)	2	0 (16 mm)
Ethiopia	363,775	459 ( 1,262 mm)	295 (812 mm)	164	138 (380 mm)
Kenya	49,513	21 (1,532 mm)	49 (987 mm)	1	23 (465 mm)
Rwanda	20,676	76 ( 993 mm)	20 (966 mm)	27	4 (180mm)
South Sudan	617,256	612 ( 991 mm)	757 (1,227 mm)	−146	92 (150 mm)
Sudan	1,226,660	364 ( 297 mm)	445 (363 mm)	−81	23 (19 mm)
Tanzania	120,506	160 (1,327 mm)	122 (1,014 mm)	38	18 (150 mm)
Uganda	236,763	301 ( 1,271 mm)	276 (1,165 mm)	25	22 (91mm)
Total (depths are means)	2,927,843	2,048 (699 mm)	2,056 (702 mm)	−8	324 (111 mm)

Sediment transport

The Nile carries sediment downstream. The movement of sediment is classified as suspended sediment (particles suspended in the water) or bedload (sediment on the river bottom that rolls or tumbles downstream). Annual sediment transport measured at several locations include:[38][w]

Gilgel Abay, Ethiopia : 7.6 million tonnes of suspended, and an additional 0.7% of bedload
Aswan, Egypt: 0.14 million tonnes of suspended, and an additional 28% of bedload
Beni Sweif, Egypt: 0.5 million tonnes of suspended, and an additional 20% of bedload
Qena, Egypt: 0.27 million tonnes of suspended, and an additional 27% of bedload
Sohag, Egypt: 1.5 million tonnes of suspended, and an additional 13% of bedload

Geological history

Further information: Sahara § Climate history

The Nile has been the lifeline of civilization in Egypt since the Stone Age, with most of the population and all of the cities of Egypt developing along those parts of the Nile valley lying north of Aswan.[citation needed] However, the Nile used to run much more westerly through what is now Wadi Hamim and Wadi al Maqar in Libya and flow into the Gulf of Sidra.[39] As the sea level rose at the end of the most recent ice age, the stream which is now the northern Nile captured the ancestral Nile near Asyut.[40] This change in climate also led to the current extents of the Sahara desert, around 3400 BCE. Although the ancestral Sahara Desert initially developed at least 7 million years ago, it grew during interglacial periods and shrank during glacial ones. The growth of the current Sahara began about 6,000 years ago.[41]

Khufu branch

The Giza pyramid complex originally overlooked a branch of the Nile that no longer exists. This branch was highest during the African Humid Period.[42][43]

Ancient Niles

The existing Nile has five earlier phases:

i) the Upper Miocenian Eonile, of about 6 million years BP;[44][45]
ii) the Upper Pliocenian Paleonile, commencing about 3.32 million years BP, and during the Pleistocene;
iii) The Nile phases, including the Proto-Nile, commencing about 600,000 years BP;
iv) Pre-Nile;[46]
v) transitioning at about 400,000 years BP to the Neo-Nile.[47][46]

Flowing north from the Ethiopian Highlands, satellite imagery was used to identify dry watercourses in the desert to the west of the Nile. A canyon, now filled by surface drift, represents the Eonile that flowed during 23–5.3 million years before present. The Eonile transported clastic sediments to the Mediterranean; several natural gas fields have been discovered within these sediments.[citation needed]

During the late-Miocene Messinian salinity crisis, when the Mediterranean Sea was a closed basin and evaporated to the point of being empty or nearly so, the Nile cut its course down to the new base level until it was several hundred metres below world ocean level at Aswan and 2,400 m (7,900 ft) below Cairo.[48][49] This created a very long and deep canyon which was filled with sediment after the Mediterranean was recreated.[50] At some point the sediments raised the riverbed sufficiently for the river to overflow westward into a depression to create Lake Moeris.[citation needed]

Lake Tanganyika drained northwards into the Nile until the Virunga Volcanoes blocked its course in Rwanda. The Nile was much longer at that time, with its furthest headwaters in northern Zambia. The currently existing Nile first flowed during the former parts of the Würm glaciation period.[45]

Affad 23 is an archaeological site located in alluvial deposits formed by an ancient channel of the Nile in the Affad region of southern Dongola Reach, Sudan.[51]

Integrated Nile

There are two theories about the age of the integrated Nile. One is that the integrated drainage of the Nile is of young age and that the Nile basin was formerly broken into series of separate basins, only the most northerly of which fed a river following the present course of the Nile in Egypt and Sudan. Rushdi Said postulates that Egypt supplied most of the waters of the Nile during the early part of its history.[52]

The other theory is that the drainage from Ethiopia via rivers equivalent to the Blue Nile, the Atbara and the Takazze flowed to the Mediterranean via the Egyptian Nile since well back into Tertiary times.[53]

R. B. Salama suggests that a series of separate closed continental basins each occupied one of the major parts of the Sudanese Rift System that during the Paleogene and Neogene periods (66 million to 2.588 million years ago): Mellut rift, White Nile rift, Blue Nile rift, Atbara rift and Sag El Naam rift.[54]

Human civilization

Ancient Egyptian civilization

European exploration

To the ancient Greeks and Romans, the upper reaches of the White Nile remained largely unknown, as they failed to penetrate the Sudd wetlands of South Sudan. Vitruvius thought that source of the Nile was in Mauritania, on the "other" (south) side of the Atlas Mountains.[59] Various expeditions failed to determine the river's source. Agatharchides records that in the time of Ptolemy II Philadelphus, a military expedition had penetrated far enough along the course of the Blue Nile to determine that the summer floods were caused by heavy seasonal rainstorms in the Ethiopian Highlands, but no European of antiquity is known to have reached Lake Tana. The Tabula Rogeriana depicted the source as three lakes in 1154.[citation needed]

Europeans began to learn about the origins of the Nile in the 14th century when the Pope sent monks as emissaries to Mongolia who passed India, the Middle East and Africa, and described being told of the source of the Nile in Abyssinia (Ethiopia).[60] Later in the 15th and 16th centuries, travelers to Ethiopia visited Lake Tana and the source of the Blue Nile in the mountains south of the lake. Supposedly, Paolo Trevisani (c. 1452–1483), a Venetian traveller in Ethiopia, wrote a journal of his travels to the origin of the Nile that has since been lost.[61][62] James Bruce claimed to be the first European to have visited the headwaters.[63] Modern writers give the credit to the Jesuit Pedro Páez. Páez's account of the source of the Nile[64] is a long and vivid account of Ethiopia. It was published in full only in the early 20th century, but was featured in works of Páez's contemporaries, like Baltazar Téllez,[65] Athanasius Kircher[66] and Johann Michael Vansleb.[67]

Europeans had been resident in Ethiopia since the late 15th century and one of them may have visited the headwaters even earlier without leaving a written trace. The Portuguese João Bermudes published the first description of the Tis Issat Falls in his 1565 memoirs, compared them to the Nile Falls alluded to in Cicero's De Republica.[68] Jerónimo Lobo describes the source of the Blue Nile, visiting shortly after Pedro Páez. Telles also uses his account.[citation needed]

The White Nile was even less understood. The ancients mistakenly believed that the Niger River represented the upper reaches of the White Nile. For example, Pliny the Elder writes that the Nile had its origins "in a mountain of lower Mauretania", flowed above ground for "many days" distance, then went underground, reappeared as a large lake in the territories of the Masaesyli, then sank again below the desert to flow underground "for a distance of 20 days' journey till it reaches the nearest Ethiopians."[69]

Modern exploration of the Nile basin began with the conquest of the northern and central Sudan by the Ottoman viceroy of Egypt, Muhammad Ali, and his sons from 1821 onward.[citation needed] As a result of this, the Blue Nile was known as far as its exit from the Ethiopian foothills and the White Nile as far as the mouth of the Sobat River. Three expeditions under a Turkish officer, Selim Bimbashi, were made between 1839 and 1842, and two got to the point about 30 kilometres (20 miles) beyond the present port of Juba, where the country rises and rapids make navigation very difficult.[citation needed]

Lake Victoria was first sighted by Europeans in 1858 when British explorer John Hanning Speke reached its southern shore while traveling with Richard Francis Burton to explore central Africa and locate the great lakes.[citation needed] Believing he had found the source of the Nile on seeing this "vast expanse of open water" for the first time, Speke named the lake after Queen Victoria. Burton, recovering from illness and resting further south on the shores of Lake Tanganyika, was outraged that Speke claimed to have proven his discovery to be the true source of the Nile when Burton regarded this as still unsettled. A quarrel ensued which sparked intense debate within the scientific community and interest by other explorers keen to either confirm or refute Speke's discovery. British explorer and missionary David Livingstone pushed too far west and entered the Congo River system instead. It was ultimately Welsh-American explorer Henry Morton Stanley who confirmed Speke's discovery, circumnavigating Lake Victoria and reporting the great outflow at Ripon Falls on the lake's northern shore.[citation needed]

Economy

The confluence of the Kagera and Ruvubu rivers near Rusumo Falls, part of the Nile's upper reaches

The Nile has long been used to transport goods along its length. Winter winds blow south, up river, so ships could sail up river using sails and down river using the flow of the river. While most Egyptians still live in the Nile valley, the 1970 completion of the Aswan Dam ended the summer floods and their renewal of the fertile soil, fundamentally changing farming practices. The Nile supports much of the population living along its banks, enabling Egyptians to live in otherwise inhospitable regions of the Sahara. The river's flow is disturbed at several points by the Cataracts of the Nile which form an obstacle to navigation by boats. The Sudd also forms a formidable navigation obstacle and impedes water flow, to the extent that Sudan had once attempted to build the Jonglei Canal to bypass the swamp.[70][71]

Nile cities include Khartoum, Aswan, Luxor (Thebes), and the Giza – Cairo conurbation.[citation needed] The first cataract, the closest to the mouth of the river, is at Aswan, north of the Aswan Dam. This part of the river is a regular tourist route, with cruise ships and traditional wooden sailing boats known as feluccas. Many cruise ships ply the route between Luxor and Aswan, stopping at Edfu and Kom Ombo along the way. Security concerns have limited cruising on the northernmost portion for many years.[citation needed]

Despite the development of many reservoirs, drought during the 1980s led to widespread starvation in Ethiopia and Sudan, but Egypt was nourished by water impounded in Lake Nasser. Drought has proven to be a major cause of fatality in the Nile river basin. According to a report by the Strategic Foresight Group, droughts in the last century have affected around 170 million people and killed half a million people.[72] From the 70 incidents of drought which took place between 1900 and 2012, 55 incidents took place in Ethiopia, Sudan, South Sudan, Kenya and Tanzania.[72]

Water politics

Further information: Water politics in the Nile Basin and Grand Ethiopian Renaissance Dam § Controversies