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The North Interior

The North Interior, which corresponds to the Sahara Desert, occupies almost 20% of the African continent. It extends from Morocco in the west to Egypt in the east. The largest part is occupied by Algeria (33%) and Libya (25%). More than 80% of the area of each of these two countries is located in this region (Map 13 and Table 51). The average annual rainfall is only 40 mm. It is even 0 mm in Niger.

Table 51: North Interior areas and rainfall by country

Rivers and discharges

The renewable water resources in the Rheris and Guir basins in Morocco are estimated at 0.82 km³/year, of which 0.67 km³/year is surface water and 0.15 km³/year groundwater. No information is available about the Western Sahara. Average rainfall is 30 mm/year in Mauritania and 70 mm/year in Mali. No information is available on renewable water resources in these countries.

For Algeria water availability and needs for 2025 have been estimated by basin [50]. Table 52 summarizes the figures for the five basins of the North Interior part of Algeria.

Table 52: Estimated water balance in the North Interior in Algeria in 2025 [50]

Available renewable water resources in the North Interior in Tunisia are estimated at 0.20 km³/year, of which 0.15 km³ is surface water and 0.05 km³ groundwater. For the whole of Tunisia it is estimated at 2.8 km³/year (of which 2.1 km³ is surface water [206]), which is about 80 % of the total internal renewable water resources, estimated at 3.52 km³/year.

Rainfall in the North Interior in Niger, occupying less than 1 % of the country, is negligible. Average annual rainfall is 10 mm in Libya, 45 mm in Chad, 105 mm in Sudan and 15 mm in Egypt. No information is available on renewable water resources in the North Interior for these countries.

Irrigation potential and water requirements

At present the irrigation water use of Morocco is 13375 m³/ha per year, in 2020 the country estimates its water use for irrigation to be 10380 m³/ha per year [149]. In the present study the water requirements for Morocco range from 7000 m³/ha per year in the north to 15000 m³/ha per year in the south. The irrigation potential has been estimated at 60000 ha [152]. Should 15000 m³/ha per year of water be used in the North Interior, the annual water use would exceed the water available, and the area should be reduced to 40000 ha at most [*].

The irrigation potential for Mauritania and Mali using renewable water resources has been considered negligible [*].

In Algeria the irrigation water requirement has been estimated at 7000 m³/ha per year [49]. The present study considers an irrigation water requirement of 12000 m /ha per year for the northern part of the basin, where irrigation schemes would possibly be situated. The irrigation potential using renewable water ranges from a minimum of 20000 ha, considering a water use of 12000 m³/ha per year and a water availability of 0.240 km³/year, to a maximum of 125200 ha, considering a water use of 7000 m³/ha per year and a water availability of 0.876 km³/year. The low estimate on water availability is based on the assumption that where the total water balance is negative this quantity is deducted from the water available for irrigation [*]. The planned use of 1.627 km /year of fossil water for irrigation in 2025 would lead to irrigation of 135600 if using 12000 m /ha per year of water and 232450 ha if using 7000 m³/ha per year of water [50, *].

The irrigation potential for the whole of Tunisia has been estimated at 563000 ha, of which 40000 ha in the North Interior [204]. With an irrigation water requirement of 14500 m³/ha per year of water [*], the total water requirement would be 0.58 km /year, which greatly exceeds the total available water resources, estimated at 0.20 km³/year. Reducing the area to 11000 ha means 0.16 km³/year of water would be required. The 40000 ha could only be irrigated by a water use of 4000 m³/ha per year.

As there is no rainfall in the North Interior part located in Niger, there is no potential for irrigation from renewable water resources [*].

The renewable water resources of the whole of Libya are estimated at 0.6 km³/year. As at present the agricultural water consumption is already 4.275 km³/year, most of it is fossil water [131]. It is planned to use an additional 2.365 km /year by 2025, bringing the total to 6.640 km³/year, The irrigable land has been evaluated at 750000 ha [131]. Estimating 250000 ha to be located in the North Interior [*] would require 2.225 km³/year of water if using of 8900 m³/ha per year of water [131]. Taking an irrigation water requirement of 18000 m³/ha per year [*] would lead to a total irrigation water requirement of 4.500 km³/year, all fossil water.

The oases in Chad are estimated to cover in total 100000 ha [85]. It is not clear what water would be used to irrigate these 100000 ha, but probably most will be fossil water. This study estimates 10000 ha to be located in the North Interior. The area in Sudan is also estimated at 10000 ha, in Egypt 50000 ha, all dependent mainly on fossil water [*].

TABLE 53 North Interior: irrigation potential, water requirements and areas under irrigation

(1) Considering 0.600 km³/year of renewable water available for irrigation: irrigation potential 60000 ha if using 10000 m³/ha per year and 40000 ha if using 15000 m³/ha per year.

(2) Considering 0.876 km³/year of renewable water available for irrigation and using 7000 m³/ha year: irrigation potential 125200 ha.

Considering 0.240 km³/year of renewable water available for irrigation and using 12000 m³/ha per year: irrigation potential 20000 ha.

(3) Available renewable water 0.160 km³/year: irrigation potential 40000 if using 4000 m³/ha.yr and 11000 ha if using 14500 m³/ha per year.

71000 ha is the sum of: 40000 ha (Morocco) + 20000 ha (Algeria) + 11000 ha (Tunisia).

Depending on the irrigation water requirements, estimates of the irrigation potential in the North Interior, based on renewable water resources, range from 71000 ha to 225200 ha.

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