The Office du Niger is a semi-autonomous government agency in Mali that administers a large irrigation scheme in the Ségou Region of the country. Water from the Niger River is diverted into a system of canals at the Markala dam 35 kilometres (22 mi) downstream of Ségou. The water is used to irrigate nearly 100,000 hectares (390 mi2) of the flat alluvial plains to the north and northeast of Markala that form part of the Delta mort. Although the French colonial administration constructed the system to produce cotton for the textile industry, the main agricultural product is now rice. Around 320,000 tons are grown each year representing 40 percent of the total Malian production. Large quantities of sugar cane are also grown in joint ventures between a Chinese company and the Malian state. The irrigation scheme uses 2.7 km3 (0.65 cu mi) of water each year corresponding to around 10 percent of the total flow of the Niger River.
Historical development The Office du Niger was first conceived in the 1910s. By the late 1920s director Émile Bélime's plans included 1 850 000 hectares of irrigated rice farms, a 3000+ km railway link to North Africa, and the forced relocation of 1-3.5 million Malian peasants. While these massive goals were never reached, tens of thousands of locals were rounded up and forced to work on the project in horrible conditions. By 1948 irrigation had only reached around 20 000 hectares, worked by less than 23 000 farmers. By the time the project was nationalized in the early 1960s, this number had grown, but only to 42 000.
Niger River
The Niger River, and its tributaries, the Sankarani, the Niandan, the Milo and the Tinkisso, rise in Guinea Highlands and the Fouta Djallon nearly 750 km (470 mi) to the southwest of Markala. The climate of both Mali and Guinea is determined by the West African Monsoon with the maximum rainfall occurring in August, but while the annual rainfall in the Guinea Highlands approaches 2,000 mm (79 in), that at Markala is only 600 mm (24 in). The short but relatively intense rainy season produces a surge of water flowing down the river system which in turn leads to the flooding of the Inner Niger Delta. Since the construction of the Sélingué hydroelectric dam on the Sankarani in 1982, some of the flood water has been retained and released later during the dry season. At the Markala dam, in an average year, the discharge of the Niger River reaches a peak of around 2,800 m3 (99,000 cu ft) in the second half of September but drops to under 120 m3 (4,200 cu ft) in the dry season between February and April. The average discharge is around 800 m3 (28,000 cu ft), but there are large year-to-year variations in the intensity of the monsoon and thus in the water flowing in the river. In a dry year such as 1989, the average discharge was only 539 m3 (19,000 cu ft), while in a wet year such as 1995 the discharge was 1,229 m3 (43,400 cu ft).
Water management The Markala Dam maintains the water in the Niger at a level 5.5 m (18 ft) above the lowest point of the river bed. Water for the Office du Niger scheme is diverted into the main irrigation canal, the Canal Adducteur, on the left bank 4 km (2.5 mi) upstream from the dam.
Irrigation system The irrigation scheme utilizes two ancient branches of the Niger River, the Fala de Molodo that runs northwards from the Niger for 135 km (84 mi) to the Alatona region and the Fala de Boky-Wéré that runs in an east-northeast direction towards the town of Macina. Before the construction of the Markala Dam these channels would fill with water during the annual flood. The Canal Adducteur has a capacity of 287 m3/s (10,100 cu ft/s) and runs for 9.8 km (6.1 mi) to the junction called "Point A". Here the water is distributed into three canals, the Canal du Sahel that flows northwards to the Fala de Molodo, the Canal Costes-Ongoïba that supplies water to the Siribala sugar cane farm and the Canal Macina that carries water to the Fala de Boky-Wéré.
Irrigation impact on the river Between 2000 and 2005 the average flow of water used by the Office du Niger was 87 m3/s (3,100 cu ft/s) but the flow varied throughout the year, reaching a peak of 135 m3/s (4,800 cu ft/s) in October and dropping to a minimum of 48 m3/s (1,700 cu ft/s) in December. On average the Office du Niger used around 10 percent of the total water in the river and although during the wet season only a small proportion was diverted, at the end of the dry season when the river discharge was at a minimum, a large proportion was used for irrigation. To satisfy some of the downstream requirements, there is an international agreement to allow at least 40 m3/s (1,400 cu ft/s) of water to flow past the Markala dam at all times. In March this left on average only 60 m3/s (2,100 cu ft/s) available for irrigation and in the driest year only 30 m3/s (1,100 cu ft/s). The water released by the Sélingué Dam to generate electrical power increased the flow of water in the dry season. The maximum amount of water diverted from the river is set by the dimensions of the canal. Until the upgrade associated with the Alatona project in 2007-12 the greatest flow was around 147 m3/s (5,200 cu ft/s) but with the upgrade to the canal system flows of up to 287 m3/s (10,100 cu ft/s) should be possible. Taking into account the 40 m3/s (1,400 cu ft/s) passing through the dam, the Niger would need a flow of at least 326 m3/s (11,500 cu ft/s) to satisfy the demand. The river only has this amount of water between July and December in an average year and between August and November in a dry year. There is a longstanding proposal to build a hydroelectric dam at Fomi in Guinea on the Niandan. The effect on the Niger at Markala would be similar to that of the Sélingué Dam: the flow would be reduced during the wet season and increased during the dry season. This increased flow during the dry season would allow the Office du Niger to divert additional water from the river.
Extent of irrigated areas Keïta et al. (2002) give the total irrigated area in January 2000 as 74,000 ha (180,000 acres) and provide the following breakdown:
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