Hydrography is essentially summarized in the Nile, which in Sudan carries out a considerable part of its course, giving rise to the episode that characterizes its regime: the merger of its two spring branches, the Blue Nile and the White Nile. The origin of the latter is in a certain sense the result – which dates back to the Pleistocene – of a “capture” exerted by the river Sūbāt on the White Nile, which once poured its waters into a large inland sea formed by the wide basin today corresponding to the amphibious zone of the Sudd, invaded mainly by papyrus and grasses. This great marshy area has, in a certain way, the function of a flywheel: it stores, through the many rivers which, like the Nile, descend from the S, the waters of the Great Lakes during the most intense period of the equatorial rains and, gradually getting rid of it, thus determines the very regular regime of the White Nile; the names of the two Niles obviously refer to the color of their waters which are strongly contrasting (especially during the flood period) due to the different nature of the materials transported. The two rivers have their confluence in Khartoum, which arose not by chance at this crucial point of Nilotic geography. Further downstream, the Nile receives the contribution of the tbarah, which descends from the northern Ethiopian highlands. The flood period is due to the great summer tribute (from July to November) of the Blue Nile, which contributes 68% of the water, while the White Nile contributes only 10% and Ātbarah for 22%. In the period of lean the White Nile contributes 83%, the Blue Nile 17%, while the tbarah contribution is zero. Between Khartoum and Lake Nubia (or Nasser) the difference in height of the river, equal to 257 m, is overcome by four cataracts. Flow rates are highly variable even during full: there were (at Aswan) maximum of 155,000 million m 3 per year and minimum of 42,000 (the average is 84 billion). For Sudan, the Nile does indeed have an important function (especially in the central belt between the two Niles, Al-Jazīrah, the island) but not as in Egypt, the well-known “gift of the Nile”; here the course is broken by numerous cataracts which obstruct its navigability and, particularly towards the south, the river has never constituted a route of penetration. For the rest, the Sudanese hydrography is represented by uidians or temporary rivers (some tending to the Red Sea or Chad), long but sterile shores bordered by a green tree band that stands out in the uniform mantle of the Sahelian savannahs and steppes. The Bahr-al-Ghazāl, a tributary of the White Nile, is the longest.
According to findjobdescriptions, vegetation is very scarce in the northern desert belt, with some species of acacias, isolated shrubs and, in the oases, the date palm. The Sahel is the domain of the Grasses; towards the S next to the steppe and shrub formations there are xerophilous arboreal plants represented by acacias, tamarisks, mimosas and euphorbias. Among the many species of acacias of the savannahs (which extend in the range of rainfall between 400 and 900 mm per year), where there are numerous baobabs, the Acacia senegal (hashab) which supplies the rubber is very widespread, especially in Darfur. arabica. Where the rainfall exceeds 900 mm per year on the reliefs there is the equatorial forest, rich in precious essences such as mahogany and fruit plants such as papaya, but is now extensively degraded and is preceded to the N by arborate savannahs. The passage from the forest to the savannah is characterized by the gallery forest, which marks the course of the rivers. Finally, in the southern part of Sudan, marsh vegetation grows with papyrus and Eichhornia crassipes, a plant of the Pontederiacee family. The presence of numerous uncontaminated territories far from inhabited areas has favored the conservation of a relatively rich wildlife. Giraffes, lions, gazelles, leopards, monkeys, baboons, hippos, crocodiles, zebras and rhinos populate the entire territory of Sudan from forests to savannahs to the desert. Lack of clean water and long periods of drought causing desertification and soil erosion are among the most serious problems facing Sudan. Furthermore, the scarce water reserves are threatened by the pollution produced by industrial waste. 4.5% of the territory is protected in the form of nature reserves, wildlife oases and 10 national parks.
During the colonial period, Sudan did not see its resources exploited: the only important achievement was the strengthening of cotton growing in Gezira. We can speak of valorisation only after the conquest of independence (1956), when the government provided for the construction of the Er Roseires dams on the Blue Nile and Khashm al-Qirbah on the Atbara; was being discontinued in 1985, because of local conflicts, the very demanding construction of the Jonglei Canal, which was to divert, channeling, the White Nile waters, preventing it impaludassero in the Sudd and obtaining the direct connection between Jonglei and Malakal. In the sixties of the twentieth century, Sudan resorted to the financial and military aid of the Soviet Union and in general favored the entry of foreign capital: this policy led to a disproportionate increase in foreign debt. In the following years the economic situation became more serious, so much so that in 1983 Nimeiry established an even more authoritarian regime: the internal conflict had the immediate consequence of the thinning out of contacts with Western countries, which, in 1995, froze their credits due to of a non-repayment to the International Monetary Fund. Furthermore, the UN Security Council imposed international isolation on Sudan (1996) due to its involvement in H. Mubarak. Since 1997, some thoughtful economic choices (including the exploitation of some oil fields) have allowed the country a slow but steady recovery and a normalization of relations with Western countries. Due to the outbreak of the war in Darfur (2003), the GDP, in sharp decline compared to the first two thousand, stood at US $ 33.903 million in 2018 and the GDP per capita at US $ 808.