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Irrigation and drainage
Evolution of irrigation development
Irrigation potential was estimated at about 2.5 million ha based on soil and water resources criteria.
Large-scale gravity irrigation started during the British colonial period (1898-1956) and the colonial agricultural policy was characterized by the promotion of cotton production in the Nile basin. Irrigation by pumping water began at the beginning of the 20th Century, substituting traditional flood irrigation and water wheel techniques.
The Gezira Scheme is Sudan’s oldest and largest gravity irrigation system, located between the Blue Nile and the White Nile. Started in 1925 and progressively expanded thereafter, in particular with its Managil expansion. It covers about 870 000 ha–one of the largest continuous irrigation schemes under a single administration in the world (UNEP, 2007)–and is divided into some 138 000 tenancies with an average size of about 8 ha (NBI, 2008). It receives water from the Sennar Dam on the Blue Nile and withdraws over a third of Sudan’s share of Nile water under the 1959 Agreement (UNEP, 2007)–from 2 km³ in 1958 to 7.1 km³ in 1998 (NBI, 2008). The scheme has played an important role in the economic development of Sudan, serving as a major source of foreign exchange earnings and of Government revenue. It has also contributed to national food security and in generating a livelihood for the estimated 2.7 million people who live in the command area of the scheme.
In the post-colonial period, it was assumed that the only sound way to bring about development would still be through large irrigation developments. The increase in Nile water allocation through the 1959 Nile Waters Agreement with Egypt led for example to the construction of the Managil extension of the Gezira scheme and of the New Halfa scheme. The New Halfa scheme is located on the upper Atbara river in the east of the country. It was partly financed by Egypt after the construction of the Aswan High Dam that created Lake Nubia, which flooded the Sudanese town of Wadi Halfa in 1964.
In the 1970s, Sudan was expected to become the “bread basket” of the Arab world, and with large investments from oil-rich Gulf nations, irrigation schemes such as the Rahad scheme, which receives its water from the Rahad river and the Blue Nile, were established on the bank opposite Gezira. Large-scale irrigated agriculture expanded from 1.17 million ha in 1956 to more than 1.68 million ha by 1977. The 1980s were a period of rehabilitation, with efforts to improve the performance of the irrigation sub-sector. In the 1990s, some small schemes were licensed to the private sector, while the four main schemes of Gezira/Managil, New Halfa, Rahad and Suki–totalling almost 1.2 million ha–remained under government control because they were considered strategic schemes, and managed by parastatal organizations known as Agricultural Corporations. In addition, there were also four major government-run sugarcane schemes. Only the fifth and largest sugarcane plantation, the Kenana Sugar Company (White Nile State), is an international public-private joint venture (with the Kuwait Investment Authority and the Saudi Arabian government). Transfer of the irrigation management of the main schemes to water user associations started in 2009.
Out of the 1 890 000 ha equipped for irrigation in pre-2011 Sudan, almost all is located in Sudan. In 2011, the total area equipped for irrigation in Sudan was 1 851 900 ha, comprising 1 725 870 ha equipped for full control irrigation (modern and traditional irrigation) and 126 030 ha equipped for spate irrigation (Table 5, Table 6 and Figure 2).
Crops were previously irrigated by shadufs (hand-operated water pump) and sequia (animal-driven water-wheel), which are now almost entirely replaced by small irrigation pumps (UNEP, 2007). Traditional irrigation is still practiced on the floodplains of the main Nile downstream of Khartoum, as well as over substantial areas along the White and Blue Nile and the Atbara river. Irrigation systems in modern irrigation include surface, sprinkler and localized irrigation systems. Spate irrigation is practiced in the Gash Delta (Kassala State) with water from the Mareb-Gash river, in the Toker Delta (Red Sea State) with water from the Baraka river, and to a lesser extent, in Abu Habil (North Kordofan state) (NBI, 2008). In spate irrigation, water from the seasonal streams is captured and redirected by diverting structures and canals to flood wide areas of arable land. Actually irrigated area depends on the volume of water carried by the river each year. The crop grows on residual moisture in the soil and no irrigation is needed. Sometimes two crops are grown in one season.
In pre-2011 Sudan, in 2000 only about 800 000 ha, or 43 percent of the total area equipped for irrigation, were actually irrigated owing to deterioration of the irrigation and drainage infrastructures. Based on the irrigated cropping calendar, it was estimated that around 993 520 ha were actually irrigated in 2011. In 1995, surface water was the water source for 96 percent of the total irrigated area land, and the remaining 4 percent were irrigated from groundwater (small tubewells). The irrigated area where pumps are used to lift water was 346 680 ha in 2000. Most irrigation schemes are large-scale and were up to recently managed by parastatal organizations known as Agricultural Corporations. They have now been transferred to water users, while small-scale schemes are owned and operated by individuals or cooperatives (Figure 3).
Traditional water harvesting practices are found in all the states of Sudan. Projects in the western part of Sudan were implemented during the 1970s, 1980s and late 1990s to combat the effects of drought by improving crop production and increasing municipal water use. However, few of those projects have succeeded in combining technical efficiency with low cost and acceptability to the local agro-pastoralist farmers. This is partially due to the lack of technical know-how, but also due to the selection of inappropriate approaches with regard to the prevailing socio-economic conditions.
Role of irrigation in agricultural production, the economy and society
The importance of the irrigated agriculture is evidenced in 2011, when it corresponded to 11 percent of the cultivated area but produced over 25 percent of the total cereals production of Sudan with almost 1.5 million tons of irrigated cereals. In addition to cereals (mainly sorghum, wheat and millet, and to a lesser extent maize and rice), the main irrigated crops are cotton, fodder, groundnuts, vegetables, sugarcane and in a lesser extent sunflower, roots and tubers (Table 5 and Figure 4). In spate irrigation, the same crops are grown except for the cash crops (cotton, groundnuts, sugarcane). The irrigation sector is of crucial importance for the country due to its reliable production, contrarily to rainfed agriculture, in particular in drought years.
In recent years, sorghum has become the main crop in terms of area in the Gezira scheme with an average of 35 percent of total area planted, followed by wheat (25-30 percent) but with a downward trend, cotton (less than 25 percent) and groundnuts (about 20 percent). Sorghum has occupied the largest area because it is both a fodder and a subsistence grain crop. However, cotton is an important crop due to its high value, as well as its importance to farmers for cash income and to the national economy for the foreign exchange it generates (FAO, 2011). The irrigated subsector contributes to almost all sugar and cotton produced in the country (NBI, 2008).
Yields in Gezira for both sorghum and wheat (2.2 and 1.7 tons/ha respectively) are above the national average yields for irrigated crops (1.5 and 1.6 tons/ha respectively), but they are well below their potential yields (3.8-5.7 tons/ ha for sorghum and 3.3-4.1 tons/ha for wheat). Sugar is well-suited to Sudan because of the abundance of fertile delta lands between the Blue and White Niles and the intense sun and availability of water. This results in some of the highest sugarcane yields in the world: 92.7 tons/ha per year in average over the 1998-2007 period.
A study at Nile basin level in 2009 evidenced that the irrigation performance and water productivity vary widely over the different irrigation schemes in pre-2011 Sudan, but the irrigation practices seem to be sustainable with irrigated land becoming greener over the previous years and the irrigation systems healthy and continuous with large water resources available. At scheme level, the modern and privately-managed West Sennar and new Kenana schemes have good irrigation results but do not seem to be sustainable in the long-term, while the El Gezira and Kassala schemes have low irrigation performances. The study also confirms that yields of irrigated agriculture in the country are generally poor with low biomass water productivity (Perry et al., 2009).
Finally, it is worth noting that large areas have been sold or leased to foreign countries or companies, in particular on the banks of the Blue Nile, thus with access to irrigation water (Rulli et al., 2013).
Women and irrigation
Women carry out a major portion of agricultural activities and bear almost the entire burden of household work, including water and fuelwood collection and food processing and preparation. Depending on the States, women are active in agriculture either only within their households (in Northern and Eastern states) or within and outside their households (in Western and Central states). Although women have equal access to land use, very few have land ownership rights, and thus can’t access credit, membership in cooperatives or extension. Fewer women than men work in the irrigated agricultural sector, however they represent 49 percent of the farmers in the irrigated sector–against 57 percent in the rainfed traditional sector. Women in the rainfed sector are primarily subsistence farmers but they also work as seasonal wage labourers in the rainfed mechanized sector, and as hired or unpaid family labourers in the irrigated sector. At the household level, women are responsible for a wide range of decision making in farming activities, even when the husband is present (UNEP, 1994).
Status and evolution of drainage systems
Due to excess rainfall and sometimes to misuse of irrigation water all irrigation schemes need drainage networks to remove any excess water from the cultivated areas. In low areas, minor drains and collector drains are constructed to remove this excess water by gravity into low areas or natural drains. Sometimes, pumps are used to take water from low lands into areas outside the scheme. Also escape drains are constructed along the main canal to carry any excess water to the nearest river or natural drain. In pre-2011 Sudan, it was estimated that about 500 000 ha were drained.