AQUASTAT
AQUASTAT

GENERAL SUMMARY

The 53 African countries have been grouped into seven regions on a basis of geographic and climatic homogeneity, which has a direct influence on irrigation. These regions, presented in Figure 1, are referred to as the Northern, the Sudano-Sahelian, the Gulf of Guinea, Central, Eastern, Indian Ocean islands, and Southern. This section briefly presents the particularities which can be observed at national and regional level, as well as trends which emerge from the information which was collected.

Water resources

The survey concentrated mostly on renewable resources. Distinction is made between the water resources generated from precipitation falling on the territory of the country or internal renewable resources, and global renewable resources which includes transfers from neighbouring countries (mostly through rivers). In both cases, the figure represents the maximum potential water resource irrespective of development potential, such as regulation of stream flow, or extractable groundwater.

TABLE 1

Regional distribution of water resources

RegionAreaPrecip.Internal renewable resources
(1000 km2)(km3/yr)(km3/yr)(mm/yr)% of total% of precip.
Northern5 753411508.71.212.2
Sudano-Sahelian8 5912 87817019.84.35.9
Gulf of Guinea2 1062 965952452.023.832.1
Central5 3297 6211 946365.248.825.5
Eastern2 9162 36425988.86.511.0
Islands (I.O.)5911 005340575.38.533.8
Southern4 7392 96727457.86.99.2
Total30 02520 2113 991132.9100.019.7

Table 1 presents, for each region, data relative to internal resources and compares these results with precipitation figures. The ratio between these two figures can beassimilated to some kind of "runoff coefficient" which would take into account recharge of that portion of the aquifers which are not connected to the river network. At regional level, this coefficient varies from 6% in arid areas to 32% in the humid zones of the Gulf of Guinea and 34% in Madagascar. Data collected in the countries show that the coefficient varies from 2% in arid countries like Libya, Niger or Botswana, up to extreme values higher than 80% in the most humid areas of Sierra Leone and Liberia. Although they cover the largest part of the continent, the Northern and Sudano-Sahelian regions contribute only respectively 1.2% and 4.3% of the total water resources of Africa. The Southern region also shows a very low runoff coefficient (9%).

Withdrawals

Table 2 shows the distribution of water withdrawals by region between the three major sectors of water use: agriculture, communities and industries. Water requirements for navigation, fisheries, mining, environment and recreation, although they can represent a significant part of the water resources, have a very low net consumption rate and are computed in very different manners by the countries, which complicates the regional analyses. For these reasons, they are not included in the computation of regional withdrawals but they appear, when available, in the country profiles.

TABLE 2

Regional distribution of water withdrawals

Withdrawals by sector
RegionAgricultureCommunitiesIndustriesTotalAs % of totalAs % of internal resources

×106m3/yr ×106m3/yr ×106m3/yr ×106m3/yr %%
Northern65 000
(85%)
5 500
(7%)
5 800
(8%)
76 300
(100%)
50.9152.6
Sudano-Sahelian22 600
(94%)
1 200
(5%)
300
(1%)
24 100
(100%)
16.114.2
Gulf of Guinea3 800
(62%)
1 600
(26%)
700
(12%)
6 100
(100%)
4.10.6
Central600
(43%)
600
(43%)
200
(14%)
1 400
(100%)
0.90.1
Eastern5 400
(83%)
900
(14%)
200
(3%)
6 500
(100%)
4.32.5
Islands
(I.O.)
16 400
(99%)
200
(1%)
20
(-)
16 620
(100%)
11.14.9
Southern14 100
(75%)
3 000
(16%)
1 800
(9%)
18 900
(100%)
12.66.9
Total127 900
(85%)
13 000
(9%)
9 020
(6%)
149 920(100%)100.03.8

For the continent as a whole, about 85% of water withdrawals are directed towards agriculture but this figure varies considerably from one region to another. Arid regions, where irrigation plays an important role in agriculture, have the highest level of water withdrawal for agriculture. The Northern region alone represents more than half of theagricultural withdrawal of the continent. In contrast, the humid regions show the lowest agricultural withdrawals: 62% for the Gulf of Guinea and 43% for the Central region, where it is the same as domestic use.

The percentage of water withdrawal over internal renewable water resources is an indicator of the importance of transfers for some countries. Libya, Tunisia, Morocco and Algeria have almost no transfer from other countries. The rate of utilization of water resources is high. This situation requires a very strict management of the resources and leads to a competition between the sectors of water use. In Libya, annual water withdrawal is higher than the volume of renewable resources, the difference coming from non-renewable resources (fossil water). Egypt and Mauritania also withdraw more water than is produced on their territory, but benefit from transfer from other countries through the Nile and Senegal rivers respectively. Niger, Somalia, Eritrea and Chad, in the Northern hemisphere, and Namibia and Botswana in the South, have few internal renewable resources but benefit from important transfers. In these countries, withdrawal is still less than their internal resources, but some of it is already taken from incoming water.

Sudan, South Africa and Swaziland have high rates of use of their internal resources, but benefit from important resources and significant amounts of incoming water.

Wastewater treatment and reuse (Tunisia, Egypt and Morocco) and desalinated water (Cape Verde, Egypt, Libya, Mauritania and South Africa) are also indicators of scarce water resources.

Irrigation potential

Due to its close relationship with water resources, irrigation potential is also unevenly distributed between the regions. It is significant to observe that this value is much less known and studied in countries benefitting from important water resources than in more arid countries. It should also be noted that the important transfers of water resources from humid to arid regions allow these latter to benefit from an irrigation potential much larger than their internal water resources would permit. This is the case of the regions traversed by the rivers Senegal, Chari and Niger in West Africa; Nile, Juba and Shebele in Eastern Africa; and Limpopo, Orange and Zambezi in Southern Africa, to name some of the most important.

The existence of inter-regional rivers and the transfers of water they implu hampers the computation of irrigation potential on a regional basis. In the same way, the computation of irrigation potential as it is presented in Table 5 may lead to a double counting of part of the shared resources, which could be avoided only through a river-basin approach. It should be noted also that the methods used in estimating irrigation potential vary from country to country, and that the choice of method can significantly affect the result, especially in humid countries. Estimates for Zaïre, for instance, vary from 1 to 40 million hectares, and irrigation potential of Congo, estimated at around 40 000 hectares in the literature, is probably only a small portion of the physical potential of the country.

Bearing in mind these uncertainties, one can notice that seven countries concentrate about 60% of the irrigation potential of Africa (Angola, Sudan, Egypt, Zaïre, Ethiopia, Mozambique and Nigeria), while at the other end of the list, 18 countries share only 5% of this potential.

Water managed areas

The diversity of water management situations encountered in Africa requests the choice of a classification which would best represent the situation of irrigation in each country. The land on which water is used for the purpose of agricultural production has been called in the text water managed areas. The term irrigated areas has been limited to that part of the water managed areas equipped with hydraulic structures: full or partial control irrigation, equipped wetland or valley bottoms and areas equipped for spate irrigation (see Table 3). The difference between the two categories comprises cultivated wetland and valley bottoms without irrigation equipment and recession cropping areas.

TABLE 3

Regional distribution of water management methods

RegionIrrigationOther cultivated wetlands/ valley bottomsFlood recession croppingTotal
Full or partial controlSpate irrigationEquipped wetlands/ valley bottomsTotal irrigation
'000 ha'000 ha'000 ha'000 ha'000 ha'000 ha'000 haas % of totalas % of cultivated land
Northern5 610
(95%)
305
(5%)
-
(-)
5 915
(100%)
-
(-)
-
(-)
5 915
(100%)
41.524.8
Sudano-Sahelian 2 263
(79%)
212
(7%)
9
(-)
2 484
(86%)
97
(4%)
296
(10%)
2 877
(100%)
20.212.1
Gulf of Guinea307
(22%)
-
(-)
163
(11%)
470
(33%)
193
(14%)
730
(53%)
1 393
(100%)
9.84.0
Central 119
(25%)
-
(-)
2
(-)
121
(25%)
352
(74%)
3
(1%)
476
(100%)
3.33.9
Eastern428
(65%)
-
(-)
6
(1%)
434
(66%)
222
(34%)
-
(-)
656
(100%)
4.62.9
Islands
(I.O.)
1 105
(100%)
-
(-)
-
(-)
1 105
(100%)
-
(-)
-
(-)
1 105
(100%)
7.740.3
Southern1 645
(90%)
-
(-)
-
(-)
1 645
(90%)
182
(10%)
9
(-)
1 836
(100%)
12.98.1
Total11 477
(81%)
517
(4%)
180
(1%)
12 174
(86%)
1 046
(7%)
1 038
(7%)
14 258
(100%)
100.09.9

Water managed areas comprise 14.3 million ha in Africa. There is a very heterogenous geographical distribution of water managed areas: the North represents more than 40% of the total. The part of water managed areas in national agriculture varies from less than 1% of cultivated land (Zaïre, Uganda, Ghana, Togo and Comoros) to 100% in the most arid countries (Egypt and Djibouti, where agriculture is impossible without irrigation). This distribution of water managed areas shows clearly the relation between climate and the role of irrigation in agriculture. In Equatorial Africa, where precipitation is greatest, rainfed agriculture is dominant. Irrigation is used for winter cropping, rice cultivation, to secure high value crops, or in wetlands and inland valleys. In Madagascar, rice cultivation on the plateaus is very developed, which explains the high percentage of irrigation in that country even though rainfall is relatively favourable.

At national level, the distribution of water managed areas is very uneven. Five countries (Egypt, Sudan, South Africa, Morocco and Madagascar), which cover 19% of Africa, hold more than 60% of the water managed areas. By adding Nigeria, Algeria, Libya, Angola and Tunisia, more than 80% of the water managed area is controlled by 10 countries. In contrast, 28 countries, covering more than 30% of Africa, share a mere 5% of water managed lands.

Among the five classes of water management presented in Table 3, one can notice that full or partial control irrigation is the most widespread (81% of the area). Among the other classes of water management, cultivated wetlands and valley bottoms and recession cropping are a majority (15% of the total). Apart from full and partial control irrigation, present in almost all countries, the other categories are usually concentrated in a few countries. Recession cropping is used essentially on the rims of the rivers Niger and Senegal and of their tributaries, or along the Logone, Chari, Zaïre, Molopo and Okavango. The fadamas of Northwestern Nigeria, classified here as recession cropping due to lack of detailed information on their degree of development, represent 70% of that category. Spate irrigation is concentrated in the Maghreb and the Horn of Africa.

When analysing irrigation techniques used in the full and partial control schemes, Table 9 shows that surface irrigation is by far the most widely used technique (more than 80% of the total). However, more than one million hectares of irrigation by aspersion have been reported, most of it being concentrated in the North (Libya, Egypt, Morocco, Tunisia), in Zimbabwe, in South Africa and, to a lesser degree, in Kenya and Zambia. In relative terms, aspersion represents the most widely used technique in Botswana, Zimbabwe and South Africa, which benefit from a relatively long tradition in this field. Finally, the most important areas under micro-irrigation are concentrated in Egypt and South Africa.

Irrigated crops

So far, the figures given in the text refer to physical areas, which is not the case for irrigated crops which are measured in terms of harvested areas. The same plot can thus be counted several times if it is used for several crops in a year.

The figures on crops in water managed areas are very incomplete and do not allow the establishment of statistical tables by country showing the distribution of the major crops under water management in Africa. However, by using all the information available, information can be obtained on about 10.5 million hectares of crops. This figure corresponds to 75% of the physical area with water control and it can thus be considered as representative of the situation of crops in water managed lands on the continent and in the major regions. Results are summarized in Table 4, in which the different crops have been grouped in six major categories.

TABLE 4

Regional distribution of main irrigated crops (partial information)

RegionRiceOther cerealsVegetablesFodderIndustrial cropsArboricultureTotal
'000 ha'000 ha'000 ha'000 ha'000 ha'000 ha'000 ha
Northern538
(11%)
2 221
(45%)
423
(9%)
1 207
(24%)
80
(2%)
459
(9%)
4 928
(100%)
Sudano-Sahelian384
(22%)
839
(48%)
61
(3%)
4
(-)
471
(27%)
1
(-)
1 760
(100%)
Gulf of Guinea993
(80%)
52
(4%)
168
(14%)
-
(-)
21
(2%)
6
(-)
1 240
(100%)
Central21
(29%)
-
(-)
4
(6%)
-
(-)
42
(59%)
4
(6%)
71
(100%)
Eastern173
(38%)
80
(18%)
158
(35%)
-
(-)
33
(7)
8
(2%)
452
(100%)
Islands
(I.O.)
880
(97%)
-
(-)
-
(-)
-
(-)
31
(3)
-
(-)
911
(100%)
Southern147
(13%)
358
(32%)
42
(4%)
353
(31%)
198
(17%)
32
(3%)
1 130
(100%)
Total3 136
(30%)
3 550
(34%)
856
(8%)
1 564
(15%)
876
(8%)
510
(5%)
10 492
(100%)

The most widespread crop is rice, which alone represents more than one third of the water managed crop area. However, large discrepancies can be seen between the regions. Cultivated mostly in wetlands and valley bottoms, rice is the predominant crop in the humid zones of the Gulf of Guinea and Eastern Africa. It is also very developed on the plateaus of Madagascar. In the Northern and Southern regions, it represents only a small portion of the total crops under water management. Among the other cereals, wheat and maize are cultivated and irrigated mostly in the countries of the North (Egypt and Morocco) and in South Africa, Sudan and Somalia. Sorghum is cultivated in the Sudano-Sahelian region, mostly as recession cropping.

Vegetables (in the table, root and tuber crops have been included in this category) are present in all regions and almost every single country. On the whole, they represent about 8% of the cultivated areas under water management in Africa. In Algeria, Mauritania, Kenya, Burundi and Rwanda, they are in fact the most widespread crops under water management. Arboriculture, which represents 5% of the total, is concentrated almost uniquely in the Northern region and is mostly composed of citrus. Industrial crops are located mostly in Sudan and in the countries of the Southern region (mostly cotton and oilseed crops). In this category, one also finds sugar cane, coffee, cocoa, oil and date palm, banana, tobacco and cut flowers. Apart from sugar cane, present in all regions except the Northern, the other crops are generally concentrated in a limited number of countries. Finally, the category grouping fodder crops and irrigated pastures, although it concerns only a very limited number of countries (concentrated in the Northern and the Southern regions) represents an important part of the cultures under water management (15%). Berseem, cultivated almost exclusively in Egypt, represents the most widespread irrigated crop in that country (1 million hectares). Other fodder crops or irrigated pasture are found principally in Morocco and in South Africa, with this last country having most of the irrigated pasture land (220 000 hectares).

Rate of use of equipped areas

One of the most frequently used indicators to assess the rate of intensification of the use of irrigated land is the cropping intensity, or the ratio between irrigated crops (including double and triple cropping) and areas equipped for irrigation. The survey showed, however, that this figure was almost never available or not reliable enough at country level. Another possible indicator is the rate of use of land equipped for irrigation, which is the part of the equippedareas actually used for production at least once in the year. This figure can vary significantly from one year to another, in particular where irrigation schemes have problems of water availability. In Table 9, the average rate of use of irrigated schemes for full and partial control is presented for each of the 30 countries where this information could be found. A regional analysis does not allow consideration of geographical trends in the variation of this value. This is probably due to the fact that it is a factor which is more related to socio-economic conditions specific to individual countries rather than to criteria related to climate and geography.

For eight out of the thirty countries, the rate of use of equipped areas is recorded to be 100% and more than half of the countries report rates of use above 80%. Conversely, countries like Lesotho, Benin, Angola, Mozambique and Eritrea show rates of use below 50%, the causes of which, very diverse, are described in detail in the country profiles. Overall, the equipped areas of the 30 countries represent 8.3 million hectares. About 1.5 million hectares, or 18% of the equipped area, is not irrigated.

Environment and health

Environmental and health problems in Africa are as serious as in other developing regions. However, in Africa, very little quantitative information is available on this aspect. Salinization of irrigated lands is a serious problem in a number of irrigation projects, such as in Egypt, Namibia, Morocco, Ethiopia and Senegal. Although water pollution by agriculture is not very serious at the continental level, due to relatively low levels of fertilizer application, fertilizer and agrochemical pollution of water resources is reported in the Northern region. Health problems related to water development, particularly vector-borne diseases such as schistosomiasis and malaria, are serious throughout the continent. Approximately 90 to 95 percent of malaria-related deaths in the world are estimated to be in Africa. Again, country-specific data, linking irrigation development and human health, are lacking in many countries. Some of these environmental and health issues, depending on availability and reliability of data, are described in the country profiles.

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