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Madagascar

Two major basin groups can be distinguished in Madagascar: the one draining to the west to the Madagascar Channel and the one draining to the east to the Indian Ocean. Rainfall in Madagascar varies from that of tropical rain forest to near desert conditions. The types of irrigation vary according to the three main ecological regions of the country: the Highlands, the West and the narrow East Coast. Because of the high altitude, in the Highlands the dry season (June-October) is cool, which limits crop production. The West is hot and the dry season is very long, up to nine months in the far south-west. Rainfall can be less than 400 mm/year. The East Coast is warm and humid with rainfall that can exceed 3000 mm/year and with almost no dry season. Irrigation potential has been estimated at 1.5 million hectares and over 70% of this area already benefits from irrigation, although large areas need rehabilitation.

TABLE 85 Madagascar: irrigation potential, water requirements and areas under irrigation

Country

Irrigation potential (ha)

Gross potential irrigation water requirement

Area under irrigation (ha)



per ha (m3/ha per year)

total (km3/year)


West

1000000

16000

16.000

700000

East

500000

14500

7.250

387000

For Madagascar

1500000


23.250

1087000

The renewable water resources are estimated at 337 km/year, which is almost 15 times the total water required for the development of the irrigation potential.

Islands

Five countries are grouped in this category, as shown in Table 86.

Cape Verde, an island group in the Atlantic Ocean to the west of northern Africa, is a very dry country. The islands of So Tome and Principe are situated in the Gulf of Guinea with very high rainfall. The three other countries are situated in the Indian Ocean to the east of southern Africa. Rainfall varies from an average of 900 in Comoros to almost 2200 mm/year in Mauritius. Table 87 summarizes the figures on irrigation and water requirements.

TABLE 86 Islands: areas and rainfall by country

Country

Total area of the country (km2)

Average annual rainfall in the basin area
(mm)



min.

max.

mean

Cape Verde

4030

60

500

230

Comoros

1861



900

Mauritius

2040

700

4000

2180

Sao Tome & Principe

960

900

7000

3200

Seychelles

455

1290

2370

1740

Total for islands

9346




TABLE 87 Islands: irrigation potential, water requirements and areas under irrigation

Country

Irrigation potential (ha)

Gross potential irrigation water requirement

Area under irrigation (ha)



per ha (m3/ha per year)

total (km3/year)


Cape Verde

2990

25000

0.075

2779

Comoros

300

5000

0.002

130

Mauritius

20000

5000

0.100

17500

Sao Tome & Principe

10700

12500

0.134

9700

Seychelles

1000

5000

0.005


Total for islands

34990


0.315

30109

Data quality assessment

Over 1000 references have been consulted, of which about 25% contained information that proved to be more or less useful for the purpose of this study, although there is a large variation in the reliability of the information. Table 88 below shows the availability of information on water resources and irrigation potential by country. The first category refers to countries for which reasonably detailed information was available on both water resources and irrigation potential. The second category refers to countries for which either less detailed information was available for both water resources and irrigation potential or reasonable detailed information for one of the two subjects and less for the other. The third category refers to countries for which little information was available on both water resources and irrigation potential.

TABLE 88 Availability of information on water resources and/or irrigation potential by country

Category

Information on water resources and irrigation potential

Countries

Number of countries

% of total number of countries

% of irrigation potential

1

Reasonably detailed

Botswana, Burkina Faso, Cape Verde, Egypt, Kenya, Malawi, Mali, Morocco, Niger, Nigeria, Senegal, South Africa, Swaziland, Tunisia, Zambia, Zimbabwe

16

30

28

2

Less detailed

Algeria, Benin, Chad, Ethiopia, Guinea Bissau, Libya, Madagascar, Mauritania, Mozambique, Namibia, Somalia, Sudan, Tanzania

13

25

31

3

Little information

Angola, Burundi, Cameroon, Central African Republic, Comoros, Congo, Cte d'Ivoire, Djibouti, Equatorial Guinea. Eritrea, Gabon, Gambia, Ghana, Guinea, Lesotho, Liberia, Mauritius, Rwanda, So Tome and Principe, Seychelles, Sierra Leone, Togo, Uganda, Zaire

24

45

41

Total

53

100

100

Reasonably detailed information for both water resources and irrigation potential was available for 16 countries out of the total of 53 countries, or 30%. Reasonably detailed information on water resources only existed for 19 countries, on irrigation potential only for 21 countries.

As expected, in general, the least information was available for the more humid countries (category 3).

The table above is related to information available at country level. For the purpose of this study, it was necessary to have information for each basic unit, which refers to the different basin parts within a country. In total there are 136 basic units (Tables 1 and 2). For only 50 basic units, or 36%, reasonably detailed information was available. For 33 basic units, or 24%, partial information was available, while for the remaining 54 basic units, or 40%, no information was available.

In total, 38 countries are located within more than one basin, which means that there is more than one basic unit in the country (see chapter 2 and Table 2). Table 90 shows the availability of information on irrigation potential at the basic unit level for these 38 countries.

TABLE 89 Availability of information on irrigation potential at basic unit level

Degree of availability of information on irrigation potential at basic unit level

Countries with several basic units

Number of countries

% of total number of countries

% of irrigation potential

Reasonably detailed information available for each basic unit of the country

Botswana, Burkina Faso, Ethiopia, Kenya, Mali, Morocco, Niger, Nigeria, South Africa, Tanzania, Tunisia, Zambia, Zimbabwe.

13

34

30

Reasonably detailed information available or part of the basic units of the country

Algeria, Chad, Egypt, Eritrea, Libya, Madagascar, Malawi, Mauritania, Mozambique, Namibia, Senegal, Somalia, Sudan.

13

34

34

Little or no detailed information available at basic unit level of the country

Angola, Benin, Burundi, Cameroon, Central African Republic, Congo, Cte d'Ivoire, Djibouti, Guinea, Rwanda, Uganda, Zaire.

12

32

36

Total

 

38

100

100

The above table shows, once again, that in general, the more humid countries have the least available information at basic unit level.

THE SENEGAL RIVER BASIN

THE NIGER RIVER BASIN

THE LAKE CHAD BASIN

THE NILE BASIN

THE RIFT VALLEY

THE SHEBELLI-JUBA BASIN

THE CONGO/ZAIRE RIVER BASIN

THE ZAMBEZI BASIN

THE OKAVANGO BASIN

THE LIMPOPO BASIN

THE ORANGE RIVER BASIN

THE SOUTH INTERIOR

THE NORTH INTERIOR

THE MEDITERRANEAN COAST

THE NORTH WEST COAST

THE WEST COAST

THF WEST CENTRAL COAST

THE SOUTH WEST COAST

THE SOUTH ATLANTIC COAST

THE INDIAN OCEAN COAST

THE EAST CENTRAL COAST

THE NORTH EAST COAST


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