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Table of contents
Hydrological infrastructure
Back to Hydrology

Hydrological infrastructure

The hydrological infrastructure in the Upper Niger Basin and Inner Niger Delta varies from large dams, small weirs to irrigated perimeters. This overview is based on recent and available information and covers existing structures as well as structures which are in preparation or development.

Dams and reservoirs

The river flow of the Niger is largely governed by rainfall, but since the construction of the Markala dam in 1947 and the Sélingué reservoir in 1982, the natural flow is altered by dams, reservoirs and water extraction along its course. The main infrastructure is shortly pictured in this Section. The irrigation zone of Office du Niger is treated separately as well as the small-scaled irrigation perimeters in the Inner Niger Delta. This applies also to the water infrastructure of the northern lakes (sluices, inlets etc.). An overview of existing and planned dams and reservoirs is listed below. Locations are given in the map below, detailed locations are shown in viewer I.

Existing and planned dams and reservoirs

Name Year Type Storage volume  Water use & loss
         
Fomi/Moussako in development Energy 1.2 – 5 km3 No data
Kogbédou-Frankonédou  in study Energy no data no data 
Diaraguela in study Energy 0.89 km3 no data
Morisanako in study Energy no data no data
Sotuba dam 1929 Energy & irrigation - 0.22 km3
Sélingué dam 1982 Energy & irrigation 2.2 km3 0.83 km3
Markala dam 1947 irrigation   -  2.69 km3
Talo dam 2006 irrigation  0.2 km3 no data
Djenné dam 2018 (?) irrigation  0.4 km3 no data 
Tossaya dam planned Energy & irrigation 4.5 km3 no data

 

dams / barrages

The Upper Niger, subdivided in Upper Niger Basin, the Bani Basin and the Inner Niger Delta, with location of existing dams, dams in development (Fomi-Moussako, Djenné) and dams in study (other dams). Note that at Fomi-Moussako two locations or in study (see text for explanation).

20180203-0011.jpg

Fomi - Moussako
The Fomi dam is planned to be constructed in the Niandan tributary in Guinea-Conakry. The reservoir is meant for hydropower in combination with irrigation and flood control. The hydrological and environmental study from 2010 (Coyne et Bellier 2010) was updated in 2017 and gives details on the hydrology, the dimensions of the reservoir, its possible management and their environmental and social impact (AECOM 2017, TRACTEBEL et al. 2017). This resulted in the consideration of four different variants (November 2017): a dam at Fomi at 393 m above sea level, and three variants at Moussako, 21.7 km upstream of Fomi, with respectively a height of 402, 396 and 388.5 m asl. The definitive choice on location, dimensions and management is currently in a process of study and consultation. The surface area of the potential reservoirs (Fomi or Moussako) is given in the viewer I.

The Fomi-variant studied in 2010 (Coyne et Bellier 2010) with a dam height of 390 m, resulted in a lake with about the same surface area as Lac Sélingué (varying seasonally between 247 and 507 km2, but much deeper, 12 m, on average at high water). That is why the storage volume was, if full, about three times as large as Sélingué reservoir (6.16 km3). The new variants differ in dam height, volume, energy production and associated impacts on the site itself (displacements, environment, agriculture) and downstream (impact on discharge and inundation). The principal parameters for the four variants considered are listed in the table below.

Table 2. Parameters of dam variants at the Fomi / Moussako site. From :  AECOM 2017
Parameter / variant Fomi
Moussako I  Moussako II  Moussako III
dam height m a.s.l. 393 402 396 388.5
Total volume 479 417 278 157
Surface area km2(total volume) 479 417 278 157
Energy production GWh/y 412.7 397.4 301.6 209.3


The Fomi reservoir will be managed in about the same way as Sélingué, as far as possible given the limitation of the relatively low inflow compared to the large volume. The reservoir will be filled between July and October. The stored water is released between December and June, as a consequence of which the future flow of the Niandan River will become in March and April much times larger, on average, than the natural flow. In the recent studies four management scenario’s are considered.

Depending on the variant, the expected potential annual electricity production varies between 209 and 412 GWH. The annual production will be variable however, due to the variation in annual flow. In a dry year the production will be much lower.

Hydro-power dams in study in Upper Guinea
Apart from the Fomi-Moussako dam, another three dams in the Upper Niger Basin in Guinea are in study. Detailed information on dimensions and progress is, however, very limited. The Kogbédou-Frankonédou dam is projected in the Milo tributary south of Kankan. This dam would have a capacity of 22 MW, and a potential of 85 MW. Near Biaraguela, on the right bank of the river, a dam is in study with a height of 395 m (storage volume 0.89 km3) and a capacity of 72 MW. The dam in study near Morisanako is situated in the Sankarani, 40 km upstream of Sélingué. This dam would have a height of 390 m and a capacity of 100 MW.

Sotuba
This is a very small hydropower plant located in the Niger, directly downstream of Bamako. The dam was built in 1929, but the run-of-river power plant is operational since 1960. It has a capacity of 5.2 MW. The estimated head between intake and outlet is 4 metres.

The plant can pass a maximum of 60 m3/s and is able to continue to work at a minimum discharge in the river of 95 m3/s. The structure itself is not very relevant for the hydrology as it has no important storage volume and as such does hardly have any impact on the flow of the Niger River. However, the same canal that feeds the plant also feeds a canal for irrigation that is able to pass 10 m3/s with a minimum river level of 316 meter, but because of the power production, the maximum amount of water diverted for irrigation is 6.37 m3/s. The water is used to irrigate the area of Baguinéda (3500 ha). According to Hassane et al. (2000) the average intake is 0.215 km3 per year.

Sélingué dam

Sélingué
The Sélingué dam and reservoir is located in Mali in the Sankarani near the Guinean border. The dam is built in 1982 and used for hydropower, and permits the irrigation of downstream rice perimeters. The Sélingué reservoir covers 450 km2 when full (2.1 km3). The management of the dam is assigned to the ‘Commission gestion des eaux de la retenue de Sélingué et du barrage de Markala’. In this Commission all stakeholders are represented.

Since the reservoir came into operation, the flow of the Upper Niger has not been fully natural. The (natural) flow of the Niger is reduced by, on average, 61% in August and by 36% in September due to the filling of the reservoir. 1.8 km3 of the annual flow is withheld by Sélingué in August and September, of which 0.5 km3 is lost due to evaporation. In the dry season 0.2 km3 per month is released, as a consequence of which the (natural) river flow roughly doubles in these months. The water stored annually in the reservoir amounts to 10-20% of the peak flow in wet years, but to 20-30% in dry years.

The difference between the inflow into and outflow from the Sélingué reservoir is a direct measure of the impact of the Sélingué reservoir on the monthly river flow. In a year with a large inflow the reservoir is already filled for a large part in August, but in a dry year relatively more water is withheld in September (to fill the reservoir). The annual variation in river flow has hardly any impact on the seasonal pattern of storing and releasing the water.

Small irrigation schemes in the Upper Niger, Mali
In the Upper Niger Basin several small or larger irrigated areas are located which extract water from the river for irrigation. Most of these are located in Mali along the Sankarani. In Guinea most of the cultivated areas found along the river are flood recession cultures, not fed by active irrigation.

Office Haute Vallée Niger (OHVN) in Mali manages, beside the irrigation scheme of Maninkoura (850 ha) 40 km downstream of Sélingué, 28 other irrigation areas with a total surface of 12 000 ha and plans to make seven other rice polders (with a total surface 3700 ha) further downstream along the Sankarani. A planned weir near Kourouba in the Sankarani would enable to irrigate the rice fields of Maninkourou (5000 ha). The total annual water intake to irrigate the 17 776 ha of rice polders along the Upper Niger Basin in Mali may be roughly estimated at 18 m3/s. This will increase to 20-25 m3/s if the Kourouba dam is functional.

Markala dam

Markala, Office du Niger
The Markala dam is located in Mali on the Niger proper, near Ségou. The dam is built in 1947 to enable irrigation under gravitation of the irrigation zone of Office du Niger, located in the Delta mort, an ancient branch of the Niger. Markala is a weir across the river used to raise the water level 5.5 m above the lowest water level of the river. The Markala dam has been operational since 1947, but it took many years before the irrigation scheme was developed (see Irrigation Zone Office du Niger).

The water intake, as registered by Office du Niger, amounts to 2.69 km3 per year, equivalent to 86.5 m3/s and does not differ for dry or wet years. Despite the gradual extension of the irrigated zone, the total water extraction remained at the same level between 1988 and 2011. Over the same period, the annual river discharge at Markala varied between 539 and 1229 m3/s. As a consequence, water use by Office du Niger is not more than 7% of a high river flow (1995), but this may increase to 16% when the flow is low (1989). The monthly water use by Office du Niger varies seasonally and is 60 m3/s in January, gradually increasing to 130 m3/s in October, decreasing to 90 m3/s in November and 50 m3/s in December. The available water supply varies between 100 m3/s in March and 3200 m3/s in September. Hence 60% of the flow is tapped in March against only a few percent in September.

Talo
The Talo dam, built in 2006 in the Bani River, is meant to facilitate irrigation under gravitation in the plains between Tounga and San. The reservoir would remain small (maximum surface 50 km2, maximum volume 0.18 km3) but its surface may be as large as 80 km2, and even larger because it actually reaches the main road between San and Bla.

The planning was to develop 20 320 ha, of which 16 030 irrigated rice fields; the rest is planned to be converted into water meadows and fish ponds. The present effect of Talo on the river flow is obvious from the seasonal variation in the water level downstream upstream at Douna and downstream at Bénény-Kegni. Since 2005, the peak flood level in Bénény-Kegni has been reduced by about 50 cm.

Djenné
The Djenné dam is located south of the town of Djenné, and is realised to counteract the water losses in the lower Bani caused by the Talo dam. The dam and rice perimeters are under construction partly operational. Due to the dam a reservoir of 150 km2 and 0.357 km3 will come into existence, 245 km2 will be flooded (Lamagat 2006). Moreover, low dikes will be made along the Bani and along the Niger near Kouakarou. Rice polders will be developed west of the dam and the plan is to rehabilitate the rice polders near Djenné and Sofara, and between Fatoma and Kouna.

Two alternatives have been worked out: either rice will be grown on 435 km2 with a controlled submersion, or 100 km2 will have a full-water-control and 335 km2 controlled submersion. In a year with an average flow, the water level in Sofara will be reduced by 30-55 cm in September, but in a dry year by 64-90 cm. The impact is less further downstream. In Mopti, where the Bani flows into the Niger, the water level is yet reduced by 5-15 cm in a year with an average flow and by 17-27 cm in a dry year.

Taoussa dam
The Taoussa dam is projected at 130 km upstream of Gao and 280 km downstream of Tombouctou, and consists of a dam of 1000 m across the Niger river valley, with a height of 18 m. As a consequence, a lake of 1572 km2 will come into existence, being, on average, about 300 km long, 5 km wide and 3 m deep. The planned dam would have a 25 MW hydroelectric power plant.

To maximize the production of electricity, the lake will be filled during the flooding period (August-January) and emptied during the deflooding period in the rest of the year. The minimum working level will be some 40 cm above the lowest gate level, by which the seasonal variation in water level will be about 4 meter, being more than the natural variation in extreme dry years but less than the variation in wet years. The flooding system in the Inner Niger Delta will not be affected, but the impact will be very large in the Niger River closer to the dam: the water level will be raised about 30 cm in Koryoumé, 70-80 cm in Gourma and 110-120 cm in Bamba. The impact on the flooding dynamics at a lower water level depends on the water management. If the gates would remain closed in the dry period, the expectation is that the northern Delta will only be partly be deflooded and that even the water level in Mopti will remain relatively high during the dry period. Potentially, the planned Taoussa dam has a huge impact on the functioning of the Inner Niger Delta.

2005-3-bko-office du niger - pvw 030.jpg

 

Irrigation zone of Office du Niger

The irrigation zone of Office du Niger consists of 115 000 ha, situated 40 km north-east of Ségou, on the north bank of the Niger. The irrigation zone is located in the Delta Mort, an ancient delta of the Niger, stretching eastwards and bordered on the west side by a dune system. It forms a secluded part of the Niger Basin since the construction of the Markala dam in the 1940s. Two old river branches (so-called Falas), connected by an irrigation canal system, act as water suppliers for agriculture in this area: one heading north through the Niono region (Fala de Molodo), the other northeast towards the Macina region (Fala de Boky-Wéré).

The irrigation zone roughly extends to the north along Fala de Molodo (Niono, Molodo, N’Debougou, Kouroumari) and to the east along Fala de Boky-Wéré (Kolongo, Ke-Macina). The production zone of M’Bewani lies in between. For more information on the development of the irrigation zone, the future extensions and the production of rice, vegetables and sugar cane, see Socio-economy.

Irrigation zone of Office du Niger

To supply the rice fields and sugar cane plantations with water, water is extracted at Markala, where the Niger river is dammed to 5.5 m above the lowest water level. This enables the use of a hierarchical hydrological system with dropping water levels, feeding larger and smaller canals. The water from the river just upstream of the weir is directed through a large main canal (Canal Adducteur) with a maximum capacity of 300 m3/s to Point A, from which it is divided between three smaller canals:

  • Canal du Sahel (175 m3/s) discharging into Fala de Molodo, leading to the irrigated areas north of Niono (Molodo, Sokolo and the surrounding area);
  • Canal Costes-Ongoïba (48 m3/s) supplying the sugar cane plantation of Siribala;
  • Canal du Macina (75 m3/s) leading into Fala de Boky-Wéré, which in its turn runs in an easterly direction towards the polders of Macina.

From each of the falas, water is let into distribution smaller canals (distributeurs), acting as a primary supply system for Sections of 3000-9000 ha, which in their turn feed a secondary supply system of partiteurs. These smaller canals cover secondary Sections of 200-600 ha, which approximately correspond to the irrigated area which can be managed by one settlement or village. Complementary to the water supply system there is a drainage system (collecteurs), leading the draining water to depression or back to the river.

From each of the falas, water is let into distribution smaller canals (distributeurs), acting as a primary supply system for Sections of 3000-9000 ha, which in their turn feed a secondary supply system of partiteurs. These smaller canals cover secondary Sections of 200-600 ha, which approximately correspond to the irrigated area which can be managed by one settlement or village. Complementary to the water supply system there is a drainage system (collecteurs), leading the draining water to depression or back to the river.

The intake of water at Markala fluctuates from 58 (January-mean 1989-2004, 59 mean 2001-2010) to 131 m3/s (October id., 129 m3/s 2001-2010). The expansion of the irrigation zone so far has been able without an increase of the total water consumption in September – February, but the intended extension (see Socio-economy) is only possible at a higher water intake. Up till now, the water consumption in September and October amounted to 120-130 m3/s and never has been higher than 146 m3/s during a month. This limit was determined by the dimensions of the hydrological system. In 2011 the capacity of the system has been enlarged.

Office du Niger consumes at present 7% of the river water in a year with a high flow, but 16% in a year with a low flow. The seasonal variation is even larger, with 60% taken in March and a few per cent in October. Office du Niger has the ambition to grow but faces two constraints: the capacity of the canal between the Niger and the irrigation areas sets a limit to the water intake in July-November, whereas the low river discharge during the dry period sets a limit to the present water use in March-May.

 

Active and controlled irrigation Inner Niger Delta

The floodplains of the Inner Niger Delta are subject to a seasonal flood pulse, which depend on the seasonal discharge of the Niger and the Bani rivers. Apart from upstream infrastructures and water extraction the timing and extent of flooding is still more or less natural in the delta. However, near Mopti and Tombouctou large embanked perimeters are situated while the number of small irrigated village perimeters (PIV’s) is growing, especially in the north (see viewer I). As such, two types of flood control and water extraction can be distinguished:

  • Flood controlled irrigation (embanked, controlled water levels), of which is 300 km2 managed by Opération Riz Mopti (submersion contrôlée) between Konna and Djenné, and 126 km2 irrigated fields (of which most between Diré and Timbuktu).
  • Irrigated Village Perimeters – Périmètres Irriguées Villageois (PIV’s) : More and more land is being irrigated. These irrigation fields are usually situated on the higher parts of the floodplains or even on areas being never inundated. That is why motor pumps are needed to pump water from the river to the fields.

 

Water management of the northern lakes

The lakes on the west bank are connected to the floodpain and filled with water most of the year. The water level in most of these lakes is managed to facilitate the cultivation of the lake shores and the lakes itself, depending on depth and inundation. The following larger lakes are distinguished:

  • Lac Tanda –near Léré, shores cultivated (in the past). No active water management
  • Lac Kabara - near Léré, shores partly cultivated (in the past). No active water management
  • Lac Tagadji – relative large, edges partly cultivated. Water levels are managed and inlet at the entrance of the lake.
  • Lac Horo –relative large and shallow lake, at low water levels fully cultivated. Water levels are managed; inlet at the entrance of the lake.
  • Lac Fati - relative deep lake, edges partly cultivated. Water levels are managed; inlet at the entrance of the lake.
  • Lac Télé - relative small and shallow lake, at low water levels fully cultivated. Water levels are managed; inlet at the entrance of the lake. The canal running east of Télé to the noth, via Lac Takara, feeds Lac Faquibine, more to the north. This canal is often blocked by sand dunes.
  • Lac Faquibine & Gouber – east of Tombouctou, of which only the eastern part holds regularly water depending on rainfall and the water level in the canal which feeds the lake. Large parts cultivated.

The lakes on the east flank are only inundated in case of a high flood and are as temporary lakes. The following larger lakes are distinguished:

  • Lac Haribongo - temporal lake/depression only flooded at high floods.
  • Lac Garou & Lac Gakoney - temporal lake/depression only flooded at high floods.
  • Lac Niangaye – temporal shallow lake flooded at high floods. Cultivated.
  • Lac Do - temporal lake/depression only flooded at high floods.
  • Lac Aougoundou - temporal lake/depression only flooded at high floods.
  • Lac Korarou - temporal lake/depression only flooded at high floods.

Maraichage a cote du Lac Horo fevr 2009 - Leo Zwarts.JPG

 

Sources and more information

  • AECOM 2017. Actualisation de l’étude d’impact environnemental et social du barrage à buts multiples de Fomi en Guinée. Phase 1. Scoping pour déterminer la configuration du barrage de Fomi. Ministère de l’Agriculture, Direction Nationale du Génie Rural. Rapport provisoire de la Phase 1 – 60543397 – Novembre 2017. AECOM.
  • Bonneval P, Kuper M & Tonneau J-P. 2002. L’Office du Niger, grenier à riz du Mali: Succès économiques, tran - sitions culturelles et politiques de développement; Le fil de l’eau et la part des homes. La Librairie de Cirad. Montpellier Cedex.
  • BRLi & BETICO 2015. Projet d’accroisement de la productivité agricole au Mali (PAPAM). Étude du Programme d’Aménagement Hydro-Agricole (PAHA) de la zone Office du Niger (ON). Rapport de Phase 1. Etat des lieux. Volume 2. Aménagements hydrauliques. Janvier 2015.
  • BRLi & DHI. 2007b. Establishment of a water management model for the Niger River Basin. Final Report (= document Rapport_final_Corps-rapport_anglais.pdf; note that the document has no title).
  • Coyne et Bellier 2010. Étude d'impact environnemental et social du projet de barrage de Fomi, Autorité du Bassin du Niger - Ministère de l'Énergie et de l'Hydraulique : Plan de gestion environnementale et sociale, Plan de développement local, Résumé de l’Étude d’Impact Environnemental et Social. Coyne et Bellier.
  • Hassane A, Kuper M & Orange D. 2000. Influence des aménagements hydrauliques et hydro-agricoles du Niger Supérieure sur l’onde de la crue du delta intérieur du Niger au Mali. Sud Sciences et technologies 5 : 16-31.
  • Lamagat JP. 2006. Etudes hydrologiques du barrage de Djenné. Etude statistiques hauteurs et débits moyens décadaires crues maximales. 70 p.  http://umr-selmet.cirad.fr/content/download/3919/28448/version/1/file/Atlas_SIPSA_2012-1.pdf
  • Liersch S, Fournet S & Koch H. 2017. Assessment of Climate Change and Water Management Impacts on the Water Resources in the Upper Niger and Bani River basins. Potsdam Institute for Climate Impact Research, Potsdam. Draft, 9 June 2017.
  • TRACTEBEL 2017. Actualisation de la faisabilité, études d’Avant-Projet Détaillé (APD) relatifs aux travaux d’aménagement dus barrage de Fomi sur la Haut Niger – Phase 1 : Actualisation de la faisabilité. P.010186 RP-1-1001 Volume 1-5. Ministère de l’Agriculture, Direction Nationale du Génie Rural. Novembre 2017. Tractebel Engineering S.A., Cedex, France.
  • Zwarts L, Cissé N & Diallo M. 2005a. Hydrology of the Upper Niger. In: Zwarts L, Beukering van P, Kone B, Wymenga E, editors. The Niger, a lifeline. Lelystad: RIZA/Wetlands International/IVM/A&W. p. 15-40.
  • Zwarts L, van Beukering P, Kone B & Wymenga E. 2005b. The Niger, a lifeline. Rijkswaterstaat/IVM/Wetlands International/A&W. p .1-304.  http://www.altwym.nl/uploads/file/361_1289481552.pdf (English) and http://www.altwym.nl/uploads/file/388_1294300622.pdf (French).
  • Zwarts L. 2012. L’impact d’un faible débit du fleuve sur l’inondation, la végétation et l’utilisation des terres dans le Delta Intérieur du Niger. A&W-report 1877. Altenburg & Wymenga ecological consultants, Feanwâlden. http://www.altwym.nl/uploads/file/489_1369388731.pdf and http://www.altwym.nl/uploads/file/489_1369388731.pdf (English).
  • Zwarts L. & van der Kamp J. 2013. Le Delta Interieur du Niger souffre-t-il d’un faible débit pendant l’étiage ? A&W-rapport 1938. Altenburg & Wymenga ecologisch onderzoek, Feanwâlden. http://www.altwym.nl/uploads/file/515_1405344669.pdf French) and http://www.altwym.nl/uploads/file/514_1405344577.pdf (English).