GEOGRAPHY AND POPULATION
Sudan is situated in the north-eastern corner of Africa and is the largest African country, with a total area of about 2.5 million km². On the north-east it is bordered by the Red Sea and it shares common borders with nine countries: Eritrea and Ethiopia in the east, Kenya, Uganda and Zaire in the south, the Central African Republic, Chad and Libya in the west and Egypt in the north. Sudan consists of a flat internal plain, lying at about 325 metres above sea level. It is crossed by the Nile river and its tributaries and by a number of mountains. In the south is the Sudd Region, the great wetland which is a maze of channels, lakes and swamps. The most remarkable feature of the Sudd area is its flatness: for 400 km, from south to north, the slope is a mere 0.01% and much of it is still flatter. The soils of the whole area are generally clayish and poor in nutrients. The northern third of the country is covered by a sandy desert with mobile and fixed sand dunes in the north-western part which is considered to be an extension of the eastern outskirts of the Great Desert.
TABLE 1 - Basic statistics and population
|Area of the country||1995||250581 000||ha|
|Cultivated area||1995||7 600 000||ha|
|- annual crops||1995||7 350 000||ha|
|- permanent crops||1995||250 000||ha|
|Total population||1995||28 098 000||inhabitants|
|Water supply coverage:|
The cultivable area is estimated to be 105 million ha, or 42% of the total area. The cultivated land is 7.6 million ha, which is 7% of the cultivable area. Only about 3 % consists of permanent crops, the remaining area consisting of annual crops.
The population of Sudan is about 28 million (1995), of which 75% is rural. The average population density is about 11 inhabitants/km, but there are substantial regional variations and half the population lives on just 15% of the land. The annual demographic growth rate averaged 2.8% between 1985-93. Some 80% of the population works in the agricultural sector. In 1994, agriculture accounted for 37.1% of Sudan's GDP and it provided over 80% of the country's exports.
CLIMATE AND WATER RESOURCES
The climate of Sudan varies from continental in the northern parts, through savannah in the centre, to equatorial in its most southern parts. Rainfall varies from 20 mm/year in the north to some 1 600 rnm/year in the far south. Average annual rainfall is 436 mm.
TABLE 2 - Water: sources and use
|Renewable water resources:|
|Internal renewable water resources||35.0||km³/yr|
|Total (actual) renewable water resources||1995||88.5||km³/yr|
|Total (actual) renewable water resources per inhabitant||1995||3 150||m³/yr|
|Total dam capacity||1995||8 800||106 m³|
|- agricultural||1995||16 800||106 m³/yr|
|- domestic||1995||800||106 m³/yr|
|- industrial||1995||200||106 m³/yr|
|Total water withdrawal||17 800||106 m³/yr|
|as % of total (actual) renewable water resources||20.1||%|
|Other water withdrawal||1995||200||106 m³/yr|
|Average groundwater depletion||106 m³/yr|
|Wastewater - Non-conventional water sources:|
|- produced wastewater||-||106 m³/yr|
|- treated wastewater||106 m³/yr|
|- reused treated wastewater||-||106 m³/yr|
|Desalinated water||1990||0.4||106 m³/yr|
Water used in Sudan derives almost exclusively from surface water resources, as groundwater is used in only very limited areas, and mainly for domestic water supply. There are large areas in Sudan where the exploitation of groundwater has been hampered by cost, as the water table is very deep. Internally produced water resources are estimated at 35 km³/year. Incoming water resources are estimated at 119 km³/year, resulting in total natural water resources of 154 km³/year.
Surface water is provided mainly by the Nile river. The main part of Nile is formed by the confluence of the Blue Nile (65%) and the White Nile (23%) in the capital Khartoum and receives, before flowing into Egypt, one more tributary, the Atbara river (12%). Both the Atbara and the Blue Nile rivers originate in the Ethiopian plateaux, while the White Nile originates from the Equatorial Lakes Plateau. The rivers of the Ethiopian catchment are marked by the extreme range in discharge between the peak and low periods, while the flow from the Equatorial Lakes Plateau is more uniform. At its peak the former provides nearly 90% of all water reaching Egypt, the latter only 5%. During the months with low flow the contributions are 30% and 70% respectively. The available average annual flow of the Nile is about 84 km³ at Aswan at the Sudano-Egyptian border, of which more than 80% between August and October. According to the Nile water agreement between Sudan and Egypt, Sudan's share is 18.5 km/year, measured at Aswan, at the border with Egypt. The agreement does not consider possible future reduction in water flowing from upstream countries.
Apart from the Nile system, there are also the seasonal rivers of Gash and Baraka in eastern Sudan. During the rainy period of July-September, the water flow, which is very violent, is drawn off into canals and spread over the land forming a very fertile delta area (spate irrigation). The water balance of Sudan is very complex, due in part to extensive evaporation from the swamps, the best known being the Sudd or Jonglei area on the White Nile in the southern part of Sudan where only half the water entering the region is estimated to flow out of it. Furthermore, from year to year variations in water resources greatly reduce the amount of water actually available for use. In the Table below, elements in the water balance of Sudan are presented, based on information from the Ministry of Irrigation and Water Resources, and including an assessment of the 80%-probability figures.
TABLE 3 - Irrigation and drainage
|1. Full or partial control irrigation: equipped area||1995||1900000||ha|
|- surface irrigation||-||ha|
|- sprinkler irrigation||-||ha|
|% of area irrigated from groundwater||1995||4.0||%|
|% of area irrigated from surface water||1995||96.0||%|
|% of area irrigated from non-conventional sources||1995||0.0||%|
|% of equipped area actually irrigated||1995||63.2||%|
|2. Spate irrigation area||1984||46 200||ha|
|3. Equipped wetland and inland valley bottoms (i.v.b.)||-||ha|
|Total irrigation (1+2+3)||1995||1946200||ha|
|- as % of cultivated area||26||%|
|4. Flood recession cropping area||-||ha|
|Total water managed area (1+2+3+4)||1995||1946200||ha|
|- as % of cultivated area||26||%|
|- increase over last 10 years||-||%|
|- power irrigated area as % of water managed area||1984||37.3||%|
|Full or partial control irrigation schemes: Criteria|
|Large-scale schemes > - ha||-||ha|
|Small-scale schemes < - ha||-||ha|
|Total number of households in irrigation|
|Total irrigated grain production||1989||670 562||tons|
|as % of total grain production||1989||20||%|
|Harvested crops under irrigation (full or partial control)||1989||1012242||ha|
|- permanent crops: total||-||ha|
|- annual crops: total||1989||1012242||ha|
|. sorghum||1989||355 320||ha|
|. cotton||1989||332 640||ha|
|. wheat||1989||165 060||ha|
|. groundnut||1989||91 140||ha|
|. sugar cane||1989||68 082||ha|
|Drainage - Environment:|
|as % of cultivated area||-||%|
|- drained areas in full or partial control irrigated areas||-||ha|
|- drained areas in equipped wetland and i.v.b||-||ha|
|- other drained areas||-||ha|
|- total drained area with subsurface drains||-||ha|
|- total drained area with surface drains||-||ha|
|Area salinized by irrigation||-||ha|
|Population affected by water-borne diseases||-||inhabitants|
According to this table, total water 'lost' by evaporation from swamps amounts to 68 km³/year. It is calculated that the reclamation of part of the swamps, through the construction of the Jonglei Canal that would direct downstream a proportion of the water considered lost each year by spill from the river and evaporation in the swamps, could lead to an increase of 10 km³/year in surface water resources. Sudan and Egypt have agreed to share the additional water equally between them.
Elements in the water balance of Sudan
|ELEMENTS||Average (km³/year)||80% reliable (km³/year)|
|1. Water resources potential:|
|- Nationally generated surface water|
|- Groundwater recharge||7||5|
|Total internal renewable water resources||35||23|
|Nilotic tributaries at border||117||102|
|Other international streams||2||1.7|
|Total natural renewable water resources||154||126.7|
|2. Currently available water resources:|
|Net available surface runoff after losses||86||70.9|
|Other regional streams||1.4|
|Internally produced surface runoff||0.7|
|Total currently available water resources||23.4|
* This figure takes into account the Sudano-Egyptian agreement of 1959 and corresponds to 18.5 km³/year at the border with Egypt.
There are four large dams, two on the Blue Nile (the Sennar and the Roseires), one on the Atbara river, and one on the White Nile. The original storage capacity of the first three reservoirs was 5.7 km³ in total, but by 1990 had been reduced to 3.2 km³ due to siltation. Apart from the Jebal Aulia dam on the
White Nile, which serves mainly to regulate the Nile flow, the other dams serve both as flood control structures and for irrigation.
Figure 1 - Water withdrawal (total: 17.8 km³ in 1994)
In 1995, total water withdrawal was estimated at 17.8 km³, of which over 94% for agricultural purposes (Figure 1).
The construction of the Jonglei Canal began in 1978 for a planned total length of 360 km and an average width of 50 metres, but the work stopped in November 1983, after 240 km, because of civil unrest in the region. By that time it also became clear that the 'water losses' in fact create resources in terms of pasture and fisheries and that the canal causes enormous human and environmental problems in the area, where millions of birds come to stay during winter. The canal would have a devastating effect on the region's eco-system and micro-climate, thereby accelerating desertification. If ever restarted, it is likely that the project would have to be revised substantially, taking into consideration the conditions of the local population and the environmental aspects.
IRRIGATION AND DRAINAGE DEVELOPMENT
Agriculture, and especially crop production, is the most significant element in Sudan's economy. Most of the cash crops are produced by irrigation, and irrigated agriculture represents about 50% of total crop production. Sudan has an irrigation potential of about 4.8 million ha considering land resources. Taking into account water resources, the irrigation potential has been estimated at almost 2.8 million ha (without considering possible large scale developments at in the enormous wetland in southern Sudan).
The total water managed area is around 1.95 million ha, or 26% of the cultivated area. Some 46 200 ha is under spate irrigation in the Gash and Tohar deltas; the rest are full or partial control irrigation schemes (Figure 2). All irrigation water comes from surface water. Most schemes are large-scale schemes, which are managed by quasi-public Agricultural Corporations (AC), while small-scale schemes are owned and operated by individuals or cooperatives. The combined GeziraManagil scheme, located between the Blue and the White Nile, constitutes one of the largest irrigation complexes in the world under single management (about 760 000 ha). It receives its water from the Sennar dam on the Blue Nile and more than 100 000 tenant farmers and their families operate the scheme in partnership with the government and the Sudan Gezira Board, which provides administration, credit and marketing services. Originally planned for the cultivation of cotton, more and more areas are coming under food crop production. Other large schemes are the Rahad Scheme, which receives its water from the Roseires dam on the Blue Nile, and the New Halfa Project (also known as Khashm AlGirba), located on the Atbara river in the east of the country. The latter project was partly financed by Egypt after the newly constructed High Aswan dam created lake Nasser, which flooded the Sudanese town of Wadi Halfa in 1964. The inhabitants were moved to the new irrigated agricultural lands where they have been growing a variety of crops for over 30 years.
Figure 2 - Distribution of the water managed areas (total 1 946 200 ha in 1990)
Although irrigated agriculture has been Sudan's greatest economic investment, returns have been far below potential. A study by the World Bank showed that, during the period 1976-1989, yields were low and extremely variable, and cultivated areas suffered gradual decline. Cropping intensity in the Gezira Scheme, dropped from 75% to 57%, as 126 000 ha were taken out of production due to siltation and mismanagement of the canals, leading to reduced availability of water. Because of bad water management, water supply is about 12% below crop requirements at crucial points in the growth cycle, while at the same time as much as 30% of the water delivered is not used by crops. The new government in Sudan reports that since 1990 there has been considerable improvement in agricultural crop production and returns. Major irrigated crops are cash crops (cotton, groundnut, sugar), wheat and sorghum (Figure 3).
Figure 3 - irrigated crops (total: 1.01 million ha in 1989)
Since independence in 1956, Sudan has established a well developed institutional infrastructure in an attempt to make its irrigation sector more efficient. At the top, the National Nile Waters Commission determines the allocation of water to each province. The Ministry of Irrigation and Water Resources (MOI&WR) is responsible for the delivery of irrigation water to the major canals and, jointly with the Agricultural Corporations (AC), for the operation of minor canals. MOI&WR is the sole authority for surface water resources assessment and development in Sudan, whereas the Groundwater Corporation has the same responsibility regarding subterranean water resources. The Hydraulic Research Station (HRS) of MOI&WR deals with the development of theoretical and applied research concerning surface water resources. Regarding the domestic water supply, the responsibility for its management and development is divided between the Urban Waters Corporation and the Rural Waters Corporation.
TRENDS IN WATER RESOURCES MANAGEMENT
Under the reforming policies of the post-1989 government in Sudan, the development of irrigated agriculture has become the crucial. There are ongoing studies for the expansion and rehabilitation of irrigation projects. Also, the construction of new hydraulic structures, such as dams and major irrigation canals, are an essential part of the planned development. Important projects include the raising the height of Roseires dam, the excavation of two major canals for water diversion from the Blue Nile, and the construction of the Merawi dam in the northern part of the country. Further irrigation development is limited by the amount of water allocated by the Nile Water Agreement with Egypt.
Three major constraints to irrigation development in Sudan are:
MAIN SOURCES OF INFORMATION
Abdelsalam A. 1991. Sedimentation in Sudan Multipurpose Reservoirs. Internal Publ. Hydraulic Research Station, Sudan.
Craig, G.M. (ed.). 1991. The agriculture of Sudan. Oxford University Press.
Howell, Paul; Lock, Michael; Cobb, Stephen (eds). 1988. The Jonglei Canal: Impact and opportunity. Cambridge University Press.
World Bank. 1990. Sudan - Reversing the Economic Decline. Country Economic Memorandum.