13 The Nile: Evolution, Quaternary River Environments and Material Fluxes Jamie C. Woodward1, Mark G. Macklin2, Michael D. Krom3 and Martin A.J. Williams4 1School of Environment and Development, The University of Manchester, Manchester M13 9PL, UK 2Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Aberystwyth SY23 3DB, UK 3School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK 4Geographical and Environmental Studies, University of Adelaide, Adelaide, South Australia 5005, Australia 13.1 INTRODUCTION et al., 1980; Williams et al., 2000; Woodward et al., 2001; Krom et al., 2002) as well as during previous interglacial The Nile Basin contains the longest river channel system and interstadial periods (Williams et al., 2003). The true in the world (>6500 km) that drains about one tenth of the desert Nile begins in central Sudan at Khartoum (15° African continent. The evolution of the modern drainage 37′ N 32° 33′ E) on the Gezira Plain where the Blue Nile network and its fl uvial geomorphology refl ect both long- and the White Nile converge (Figure 13.1). These two term tectonic and volcanic processes and associated systems, and the tributary of the Atbara to the north, are changes in erosion and sedimentation, in addition to sea all large rivers in their own right with distinctive fl uvial level changes (Said, 1981) and major shifts in climate and landscapes and process regimes. The Nile has a total vegetation during the Quaternary Period (Williams and catchment area of around 3 million km2 (Figure 13.1 and Faure, 1980). More recently, human impacts in the form Table 13.1). of land use change over the last few millennia and large The Nile Basin supports a vast range of ecosystems dam construction over the last hundred years or so, (Rzoska, 1976) and has played a central role in the devel- have had major impacts on the hydrology and sediment opment of a rich diversity of cultures (Wendorf et al., budget of the Nile Basin. The river basin straddles 35° of 1976; Welsby, 1998, 2001; Shaw, 2003). It has been an latitude (4° S to 31° N) encompassing a wide variety of important corridor for the movement of people and animals climates, river regimes, biomes and terrains – from the throughout the Quaternary and the lower Nile and delta Equatorial lakes plateau of the White Nile headwaters to saw the rise of the Kingdoms of Egypt (Davies and Fried- the delta complex in the Eastern Mediterranean Sea man, 1999) and their great irrigation-based civilization (Figure 13.1). It is unique among the large exotic rivers (Hassan, 1988). Today over 180 million people live within of the world in that today it fl ows for almost 2700 km the basin and about half this number are almost totally through the Sahara Desert without any signifi cant peren- dependent on Nile fl ows for economic and domestic nial tributary inputs. Of all the world’s rivers with catch- needs. While much of the basin is sparsely populated, ments greater than 1 million km2, the Nile has the lowest rapidly growing urban centres, most notably Cairo (popu- specifi c discharge, 0.98 litres s−1 km−2 at Aswan (Shahin, lation >16.5 million) and greater Khartoum (population 1985) – although base fl ows and the summer fl ood were >6 million) – and extensive tracts of agricultural land on signifi cantly higher in the early Holocene (Adamson the valley fl oor and delta – are heavily or totally reliant Large Rivers: Geomorphology and Management, Edited by A. Gupta © 2007 John Wiley & Sons, Ltd 262 Large Rivers Mediterranean Sea Dams A Aswan B Jebel Aulia C Khashm el Girba Cairo D Sennar E Roseires F Owen Falls Nile 1 Cataracts Marshes EGYPT LIBYA 1 A Lake Nasser R Lake Nubia 2 Wadi Halfa e d S Nile ea 3 5 Dongola 4 Atbar Wadi Howar 6 a CHAD ERITREA Khartoum C B Blue Nile Wadi el Melk SUDAN White Nile D Lake Tana E Malakal Sobat ETHIOPIA CENTRAL AFRICAN Bahr REPUBLIC el Jebe Juba l UGANDA Lake CONGO Lake Turkana Albert F Lake Kampala Edward Lake KENYA Victoria N RWANDA 0 500 km TANZANIA Figure 13.1 Map of the Nile Basin showing the drainage network, basin states, and major dams The Nile 263 Table 13.1 Geographical, hydrological, and water resource data for each of the 10 countries of the Nile Basin (based on sources in UNEP, 2000) Country Area of country Average rainfall Internal Actual The dependency Population in the within the Nile across the basin in renewable renewable ratio = the Nile Basin in 1990 basin (km2) and its each country for water water percentage (millions) with the percentage of the minimum and resources resources difference percentage of the total basin area (in maximum years (IRWR) (ARWR) between the country’s population parentheses) (mm) (km3 year−1) (km3 year−1) ARWR and the in the basin (in IRWR parentheses) Burundi 13 260 (0.4) 895 to 1570 3.6 3.6 0 3 204 (58) DR Congo 22 143 (0.7) 875 to 1915 935 1019 8.2 1 838 (4) Egypt 326 751 (10.5) 0 to 120 1.7 58.3 96.9 47 599 (85) Eritrea 24 921 (0.8) 240 to 665 2.8 8.8 68.2 0.918 (30) Ethiopia 365 117 (11.7) 205 to 2010 110 110 0 19 454 (35) Kenya 46 229 (1.5) 505 to 1790 20.2 30.2 33.1 9 129 (32) Rwanda 19 876 (0.7) 840 to 1935 6.3 6.3 0 5 731 (72) Sudan 1 978 506 (63.6) 0 to 1610 35 88.5 77.3 20 893 (74) Tanzania 84 200 (2.7) 625 to 1630 80 89 10.1 4 878 (16) Uganda 231 366 (7.4) 395 to 2060 39.2 66 40.9 15 999 (75) Total 3 112 369 (100) 129 643 on Nile fl ows for irrigation and power generation. The of the basin. Local water resources are minimal in the arid population of Egypt (>65 million in 2001) is expected to and semi-arid regions of Egypt and Sudan (Table 13.1) double by 2050 and it already uses the largest share of the and evaporation and seepage losses are high in this part annual water budget. The spatial pattern of rainfall inputs of the basin (UNEP, 2000). The Merowe Dam near the across the Nile Basin is highly variable and because Sudan fourth cataract in northern Sudan is expected to be com- and Egypt abstract the greatest volumes for irrigation – pleted in 2008 and it will treble the nation’s hydropower and have the highest water resource dependency ratios capacity. Hydroelectric output from the Aswan High Dam (Table 13.1) – the allocation and use of Nile waters con- never lived up to expectations owing to seepage losses tinues to be a highly charged political issue within the 10 and serious underestimates of evaporation losses. The basin states (Howell and Allan, 1994). Merowe project will create the fi rst dam on the main Nile The dominant water resource management and fl ood in Sudan and will involve the resettlement of 50 000 control strategy of the twentieth century saw the develop- people as well as the loss of many archaeological sites ment of major river impoundments in the basin (Figure (Askouri, 2004). 13.1). Over the same period, as the population of Egypt This chapter reviews the evolution of the river and its and its irrigation schemes grew apace, the allocation and present day hydrology and fl uvial geomorphology. It also use of Nile waters emerged as a source of major interna- summarises the response of the Nile Basin to Late Pleis- tional political tension (Collins, 1990; Howell and Allan tocene and Holocene climatic changes as this provides 1994) and Nile Waters Treaties were signed in 1929 and important context for the contemporary fl uvial environ- 1959. The fi rst phase of construction of the Aswan High ments of the basin. The suspended sediment budget of Dam was completed in 1964 (the fi nal phase ended in the basin and offshore regions is also discussed and the 1971) and other major twentieth century dams include the impacts of the major water resource management develop- Jebel Aulia (1937) on the White Nile and the Roseires ments on water and sediment fl uxes are assessed. Dam (1966) on the Blue Nile (Figure 13.1). Since the long-term fl ow records for the Nile exhibit considerable 13.2 NILE BASIN RIVER ENVIRONMENTS annual variability (Hassan, 1981; Sutcliffe and Lazenby, 1994), the major water storage schemes hold considerable According to Said (1981) the Nile Basin encompasses fi ve strategic importance for water resource management, major regions that differ from one another in structure and power generation and fl ood control. These schemes are geological history (Figures 13.1 and 13.2). These are partly a response to the fact that most of the fl ows are listed below and the characteristic fl uvial environments of generated in headwater areas that cover only about 20 % each region are briefl y described: 264 Large Rivers Figure 13.2 Long profi le of the Nile from the White Nile headwaters to the Mediterranean Sea (after Said, 1994). Note that the Blue Nile is not shown The Nile 265 (1) The Equatorial lake plateau in the White Nile head- history of the Nile Basin and neighbouring regions and waters with densely forested, tropical catchments with have related these geological phenomena to the organiza- perennial fl ow regimes. tion of the drainage network, to the location of major (2) The Sudd region and central Sudan with low sedimentary basins, and to major changes in the former gradient fl oodplains, extensive swamplands and extent of the catchment.