Soudan Méridional = Southern Sudan
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SOUDAN MERIDIONAL SOÙTHERN SUDAN Coordinateur Co-ordinator Henri J. DUMONT, Jeannine PENSAER T, Asie d MOGHRAB Y, and/et Roland G. BAKLEY Soudan ineridional - 212 - INTRODUCTIQI The Sudd swamps result Prom the White Nile crossing a very flat eountry. As a result, the river is bordered by an ever widening fringe of marshes, which may amount to several tens of kilometers across. Inside the Sudd, the river divides into two main branches, the Bahr el Jebel and the Bahr el Zeraf, each one winding its way through the plain, and each with a main channel parallelled by numerous, equally winding aide-channels, which are regularly @‘blocked” by floating islands, mainly eomposed of Papyrus and Phragmites. The surface area of these fringing swamps> along the Bahr el Jebel alone, amounts to between 8-10 000 km*. An annual flood oecurs, partly due to local precipitation, but mainly as a consequence of rainfall on the East African Plateau. It inundates .a season floodplain to a distance of up to 80 km from the main river channel. Peak values occur in April-&%ay and the maximum extent of the swamps then reaehes 70 000 kJ. Because SO much water thus becomes trapped in the Sudd, considerable losses occur and up to 50% of the annual flow may be lest through evaporation and seepage. TO reduce these losses, the Jonglei Canal is presently being dug, that Will short-circuit the swsmps to the east, between Jonglei and an area south of the Sobat-White Mile junction. The Bahr el Chacal joins the Bahr el Jebel in the North-West of the swamp area. It is a very different river, with a much less luxurious vegetation. Lakes are found in several areas of the Sudd: Lakes Papiu and Nuong along the Equatorial Nile are very different Erom Lakes Ambadi and No on the Bahr el Ghazal, both chemically and biologically. The Maehar Narshes are situated to the North-East of the Sudd. They drain only partially towards the White Nile through the River Adar, and have received very’little scientific attention SO far. The Sudd is extremely rich botanically, and also has more bird and fish species than any other area of the Nile Valley. Its invertebrate community is also rich, but partly unstudied. Its zooplankton is typically Nilotic. The phytoplankton of the Bahr el Ghazal is remarkable for its high degree of endemieity. North of the Sudd, Lakes Kunde and Keilack occur. These are significant sites, because they may be remnants of a former -overflow between the Nile and Chad Basins. %NTl%GDUCTLCN L’arrivée du Nil Blanc dans une plaine est a l’origine des marécages du Sudd. Le fleuve est borde de marecages qui s’étendent de plus en plus et peuvent atteindre jusqu’à des dizaines de kilometres de largeur. A l’intérieur même du Sudd, le Nil se divise en deux branches principales, le Bahr el Jebel et le Bahr el Zeraf, qui serpentent dans la plaine. De nombreux chenaux latéraux, parallèles au cours principal des deux branches, serpentent également et sont regulièrement obslrués, par des îles flottantes composées de Papyrus et de Phragmites. La surface des marécages qui bordent le Bahr el Jebel seul, peut couvrir de iOO0 à 10 000 km2. Sous l’effet des pluies locales mais surtout des pluies sur le Plateau Occidental Africain, la crue annuelle peut recouvrir sur une plaine d’inoadation saisonnière s’etendant jusqu’a 80 km du cours principal de la rivière. La superficie totale des marécages peut atteindre 70 000 km2 pendant les crues en Avril-Mai. De telles retenues d’eau dans le Sudd, ereent des pertes considérables par Qvaporation et infiltration, Qvaluées jusqu’a 50% du débit annuel. Afin de réduire ces pertes, un canal est en cours de construction entre Jonglei et le sud du confluent du Nil blanc et de la rivière Sobat. Ce canal court-circuitera les marais de l’est. - 213 - Southeru sudan Soudan du Sud - Sudd Southern Sudan - Sudd - lo” Soudan meridional . 0 I 100 200 km ,’ 3’ #’ Mechar Mershes Khor bed Qrassland Hyparrhenl-.___- rut8-- type with limited Acacia-Bslanltep lorest $tata Incrassata type Qrasaiand with Acacia-Balanitep farest THE SLJDD L-J Hiphland areas - 215 - Southern Sudan Le Bahr el Ghazal rejoint le Bahr el Jebel au nord-ouest du Sudd. C’est une rivière très différente, a végétation relativement pauvre. Des Lacs se trouvent a plusieurs endroits du Sudd: les lacs Papiu et Nuong jalonnant le Nil Equatorial différent des lacs Arnbadi et No situés le long du Bahr el Ghazal, tant au point de vue chimique que biologique. Au nord-est du Sudd, les marécages de’ Machar, très peu étudiés jusqu’à présent, ne sont que partiellements, reliés au Nil par la rivière Adar. Le sudd est une région remarquablement riche au point de vue botanique, et la faune ichtyologique et ornithologique y est plus variée que partout ailleurs dans la vallée du Nil. Sa faune d’ invertébrés est aussi très riche mais relativement peu étudiée. Le zooplancton est typiquement nilotique. Le phytoplancton est remarquablement endémique dans le Bahr el Ghazal. Au nord du sudd, les lacs Kunde et Keilack, sites remarquables, sont supposés être des vestiges d’un débordement entre les bassins du Nil et du Chad. TRAVAUX REALLSESIPUBLISIIED WORKS Exploration Baker 1866, 1868; Gage lQS0; Garstin 1904; Hull 1956; Urne 1906; Liddell 1904; noorhead 1960, 1962; Shinnie 1940; Swedish tixpedition to Egypt and the White Nile (1904-1929). Divers/General Adam 1971; Bailey & Gobb 1984; Berry 6 Whiteman 1968; Cloudesley-Thompson 1984; Dumont 1979, 1986a; Bntz 1976; vergusson 1921; Green & a. 1984; Bammerton 1966, 1972; IIerbst 1954; Ilope 1902; Irurst 1933, 1957; Burst & Phillips 1931; Kassas 1971; Langlands 1962; Hef it-Babtie 1983a,b; noorhead 1960, 1962; Rzoska 1966 > 1976a; Swedish Expedition to Egypt and the White Nile (1904-1929); UNEP/FAG 1977; Williams & Faure 1980; Wright 1949, 1951. Bcology/Rcologie Beshir,& El Hoghraby 1980; Kassas ïQ/L; Higahid 1947, 19480; Saeed 1972. Glimatology/Glimatologie Cloudsley-ï’hompson 1966, 1984; Irurst & Phillips 1931; Williams 6; Adamson 1974. Geology/GBologie Andrew 1948; Khalil & Bl Badri 1973; Haley 1969; Said 1981; Sanford 1949. Geochemistry/GQochimie Drover &, Bishai 1962; Khalil & El Badri 1973. Pedology/Pédologie Bunting Technical Services Ltd 1964, 1965. Geomorphology/Géomorphologie Awad 1928; Uerry 1960, 1962a,b, 1963, 1976; Berry & Whiteman 1968; Ghristy 1917, 1933 ; Ilowell 1945, 1953; IIurst & Black 1946; IIurst & Phillips 1931; IIussein 1964; Lyons 1909; Hefit-Babtie 1983a; Tottenham 1926; UNEP/FAO 1977. Soudan meridional - 216 - Iiydrology/Iiydrologie Euroconsult Jonglei Environmental Aspects 1978; Hammerton 1964, 1965, 1966, 1972, 1973; Howell 1953; Hurst 1927, 1933, 1950, 1957; Hurst Q Black 1946; Hurst & Phillips 1931, 1932, 1938; Hussein 1964; Ibrahim A M 1984; Jonglei Executive Organ 1982; Jonglai Investigation T@am 1952, 1954; Kamal 1977; Krishnamurthy 1981; Kurdin 1968; NaCDonald 1932; Mefit Babtie 1983a; Higahid 1952a,b; Hinistry of Irrigation' and H.E.E. 1975; Ministry of Irrigation, Khartoum 1955, 1957. 1975; Nohammed 1977; Moorhead 1960, 1962; Rz&ska 1976d,e,f; Sutcliffe 1974; Sutcliffe & Park 1982; UNEP/FAO 1977. Physico-chemistry/Physicochimie des eaux AL Hafeez B Saudi 1971; Beam 1906, 1908; Beauchamp 1956; Bishai 1959, 1961b. 1962; Boutros 1972; Burden 1956; Desougi 1984; Drover & Bishai 1962; El yoghraby 1973C; Entz 1976; Gay 1958; Hammerton 1963; Khalil & Badri 1973; Kurdin 1968; Tallin8 1957, 1976%. Hydrobiology/Hydrobiologie Abdullahi 1979; Drar 1951; Bammerton 1964, 1965, 1966, 1972, 1973; Hydrobiological Research Unit, Univ. Khartoum 1953-1973; Befit-Babtie 1983a; Rzoska 1958, 1961, 1974, 1976a; TalEing & Rzoska 1967. Limnology/Limnologie Dumont 1979, 1986a; Nefit-Babtie 1983b; Rzoska 1974; Saeed 1976. Algae/Algues Abdel Karim â Saeed 1978; Bastow 1960; Brook 1954; Gronblad 1962; Gronblad & al. 1958; Hammerton 1963; Karim 1961; Karim & Saeed 1978; Pankow 1979; Prowse 1955; Prowse & Talling 1958; Saeed 1972, 1976; Talling 1976b; Talling & Rzoska 1967. Hacrophytes Ahti --et al. 1973; Bani 1968; Brown 1905; Denny 1984; Desougi 1980; Drar 1951; El Hoghraby 1975; Evans-Pritchard 1950; Halwagy 1961; Nefit-Babtie 1983a,b; Higahid 1947, 1948a,b, 1952a,b; Nohammed K A 1951; Rzoska & Wickens 1976; Thompson & Hamilton 1983; Thornton 1957; Youssif 1974. Gyperus papyrus Faure 1956; Gaudet 1979; Thornton 1957. Eichhornia crassipes Abdalla & Abdel Hafeez 1969; Abdel Hafeez 1975; Abu-Gideiri & Yousif 1974; Bank 1966; Batanouny b Fikry 1979; Bebawi 1972; Beshir 1975a,b; Beshir d Koch 1979; Bishai 1962; Davies 1959; Davis 1959; Desougi 1974, 1980, 1984; El Hoghraby 1975; El Tigani 1975; ,Fariz 1972; Field Survey on Fruit Setting by Eichhornia crassipes (1972); Freidel 1975, 1979; Freidel & Beshir 1979; Gay 1957, 1959, 1960a,b; Gay 6, Berry 1959; Gayed 1963; Heinen â Ahmed 1964; Irving & Eeshir 1982; Kamal h Little 1970; Little 1965; Loomis 1967; Hohammed 1975a.b.c; I¶ohammed & Bebawi 1972a,b; Nukhtan 1967; Dbeid 1962, 1975a,b,c; Obeid & chadwick 1964; Obeid â Tag El Seed 1975; Osman et a. 1975; Pettet 1964; Tag El Seed 1972, 1978; Tag El Seed 6 Obeid 1975; You&f 1974. - 217 - Southern Sudan Invertebrates/Invertebres Plankton/Plancton Abu-Gideiri 1969a,b; Abu-Gideiri & Yousif 1974; Ahmed M A 1970; Ali 1977; Brook & Rzoska 1954; Dumont 1986b; Ekman 1904; Rl Moghraby 1972, 1973b, 1977; Green 1984b; Kiefer 1978; Monakov 1966a,b, 1971; Rzoska 1952, 1968, 1976b; RzOska --et al. 1955; Smirnov 1971; Talling â Rz&ska 1967; Von Daday 1910. Divers/General Abdalla & Bakr 1975; Abu-Gideiri 1969a,b; Abu-Gideiri â Yousif 1974; Ahmed H A 1970; Ali 1977; Amirthalingham 1965; Anderson et a1 . 1974; Balfour-Browne 1947; Brook & Rzoska 1954; Brtek 1972; Bryant 1935; Cranston -et --a1 1981; De Han 1901; De Ridder 1984; Dumont 1986a,b; Ekman 1904; Rl Hag 1972; 01 Moghraby 1972, 19730, 1977; Faure 1956; Flower 1900, 1931; Frandsen 1979; Freeman 1950; Fryer 1979; Gassouma 1972; Ghabbour 1976; Gibbins 1935; Gordon 1930; Green 1984a,b; Green et a1 .