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The Volta Basin

The Volta basin occupies almost 28% of the total West Coast and is shared between six countries (Map 16 and Table 64).

Rivers and discharges

The most upstream part of the Volta basin is located in Mali, where it occupies less than 1 % of the area of the country. One river, the Sourou, crosses the border from Mali to Burkina Faso, but there is almost no flow in this river.

Table 64: Volta basin areas by country

Two-thirds of Burkina Faso are within the Volta basin. The Black Volta (Monhoun), Red Volta (Nazinon) and White Volta (Nakambé) all have their sources in Burkina Faso.

The Black Volta originates in the south-west of the country, flows north-eastwards and then turns south. In the south, it becomes the border, first between Ghana and Burkina Faso and then between Ghana and Côte d'Ivoire. When leaving Burkina Faso, its discharge is about 5 km³/year; when entering Ghana, it is about 6 km³/year. The Red Volta originates in the central part of Burkina Faso, near Ouagadougou, and flows south-eastwards to the border with Ghana. After crossing the border, it joins the White Volta. The White Volta originates in the north of Burkina Faso and also flows south-eastwards to the border with Ghana. The total annual discharge leaving Burkina Faso through the Red and White Volta Rivers is estimated at 3.7 km³/year.

The Pendjari River originates in the north-west of Benin. It flows north-east, then turns sharply to the west to become the border, first between Burkina Faso and Benin, then between Togo and Benin for just a short distance before entering Togo with a total annual discharge of 2.2 km³. In Togo, which it crosses in the north, here called the Oti River. Further downstream it becomes the border between Togo and Ghana. Entering Ghana further south, its discharge is estimated at 11 km³/year.

Many other tributaries have their source within Ghana, but especially in the northern savannah part most of these water courses run almost dry after the rains. The groundwater here is low yielding and cannot be relied upon for extensive irrigation [113]. In the south a dam has been constructed at Akosombo for hydropower. Behind this dam, one of the world's largest artificial lakes has been created, Lake Volta, with a surface area of 8500 km² and a capacity of 148 km³. The average annual discharge flowing to the sea is estimated at about 38 km³.

Irrigation potential and water requirements

The irrigation potential in Mali, occupying less than 1% of the country and with very few surface water resources has been considered negligible [*].

The irrigation potential in Burkina Faso has been evaluated at 142000 ha, distributed as follows over the different sub-basins [67, 69, 72, 73]:

Of these 142000 ha, about 20000 ha are valley bottoms and 7000 ha small areas irrigated by small earth dams.

The irrigation potential of Benin has been evaluated at 300000 ha, but no details are available on location [57]. It is estimated that 30000 ha are located in the Pendjari Basin [*].

Table 65: Irrigation potential and water requirements by sub-basin in the Volta basin in Burkina Faso

The irrigation potential of Togo has been evaluated at 180000 ha, of which 100000 ha are valley bottoms [21a]. No details are available on location. As the Volta basin occupies about half of Togo, half of the irrigation potential, or 90000 ha, is estimated to be within the Volta basin [*]

Of the irrigation potential of 475000 ha for the whole of Côte d'Ivoire [21a], 25000 ha are estimated to be in the Volta basin [*].

The potential for irrigated rice production in the inland valley swamps and the floodplains within Ghana has been evaluated at 1.9 million hectares, of which 346000 ha are estimated to be suitable for fully controlled irrigation development [114]. No figures are available on location. About two-thirds of the country being within the Volta basin, an irrigation potential of 1.2 million hectares has been tentatively estimated for this area [*].

Table 66: Volta basin: irrigation potential and water requirements

The total annual flow to the sea, 38 km³, exceeds than the total annual irrigation water requirements for the whole basin, 28.5 km³. Comparing the water requirements in the different parts of the basin with water availability, the balance remains positive everywhere.

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