Where the Indian Ocean and Atlantic Ocean Meet

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The Indian Ocean coast

The southern and south-western part of the Indian Ocean Coast is wholly situated in South Africa. The eastern part is shared between Swaziland, South Africa and Mozambique. The north-eastern part is shared between Zimbabwe and Mozambique (Map 20 and Table 77). Its total area represents 2.2% of the area of the continent.

TABLE 77 Indian Ocean Coast: Areas and rainfall by country

Country	Total area of the country (km�)	Area of the country within the basin (km�)	As % of total area of basin (%)	As % of total area of country (%)	Average annual rainfall in the basin area (mm)
					min.	max.	mean
Swaziland	17364	17364	2.6	100.0	600	1020	780
South Africa	1221040	358648	54.0	29.4	125	1270	585
Zimbabwe	390760	102047	15.4	26.1	375	1685	650
Mozambique	801590	185726	28.0	23.2	470	1770	885
Total Ind. Oc. Coast		663785	100.0		125	1770	680

Rivers and discharges

Of the four major rivers in Swaziland, two originate inside the country, the Mbuluzi and Ngwavuma rivers, and two in South Africa, the Komati and Usutu rivers. Total inflow from South Africa to Swaziland is 1.8 km�/year. Total outflow from Swaziland is 3.5 km�/year, of which 2.3 km� flow directly into Mozambique to the Umbulezi and the Maputo rivers. The remaining 1.2 km� first enter South Africa before flowing into Mozambique, in the south towards the Maputo River and in the north towards the Incomati River. The Sabie River is another tributary of the Incomati River originating in South Africa.

Within South Africa, perennial rivers occur over only one quarter of the area and mainly in the southern and south-western Cape province and on the eastern plateau slopes. However, even the perennial rivers are very irregular and have important seasonal variations. The surface water resources in the Indian Ocean part are estimated at 31 km�/year, of which about 21 km�/year are exploitable. Less than 10 km�/year are available for agricultural purposes.

The Save, Buzi and Pungo� rivers originate in Zimbabwe and all flow to Mozambique. Although the catchment area of the Pungo� River in Zimbabwe is only 5 % of the total catchment area, about 26% of the annual runoff originates from this area [155].

Irrigation potential and water requirements

For Swaziland the following irrigation potential figures are given for the country, based on land and water availability [197]:

TABLE 78 Water resources, irrigation potential and water requirements by sub-basin in Swaziland

Basin	Inflow from RSA (km�/yr)	Produced in country (km�/yr)	Outflow (km�/yr) (ha)	Irrigation potential (km�/yr)	Water demand
Lomati-Komati	0.738	0.415	1.153	17 925	0.161
Mbuluzi	0	0.352	0.352	24 280	0.219
Usutu	1.032	0.904	1.936	45 875	0.413
Ngwavuma	0	0.106	0.106	5 140	0.046
Total	1.770	1.777	3.547	93 220	0.839

In South Africa, about 9 km�/year of water are estimated to be available for agricultural purposes in the Indian Ocean Coast in 2010 [190]. Table 79 summarizes the water resources, irrigation potential and water requirements for the different basins (see also Map 20).

TABLE 79 Irrigated areas, water availability, water requirements and irrigation potential in the Indian Ocean Coast in South Africa

Sub-basin	Actual irrigated (ha)	Actual water use (km�/yr)	Water available (km�/yr)	Irr. wat. requirem. (m�/ha.yr)	Irrigation potential (ha)
H - S	200000	2.041	1.906	10000	190 600
T-W	158 000	1.547	5.898	10000	589 800
X	68 000	0.681	0.974	10000	97 400
Total IOC	426 000	4.269	8.778		877 800

For the whole of the Indian Ocean Coast in South Africa the irrigation potential is 877800 ha, which is more than twice the area irrigated at present, estimated at 426000 ha [*].

The surface water resources produced in the upper Save basin in Zimbabwe are estimated at 4.052 km�/year, which corresponds to the potential yield [216]. After deducting the amount of water already committed, the quantity of water still available is 2.542 km�/year. Of this quantity, about one-third, or 0.847 km�, can be considered as potentially available for the development of irrigation. The surface water resources produced in the upper Buzi and Pungo� basins in Zimbabwe are estimated at 1.024 km /year, of which 0.922 km /year is still available and one - third of this, or 0.307 km�/year, for the development of irrigation.

At present 124804 ha have been developed or planned for irrigation in the upper Save basin [216]. Based on land and water and considering an irrigation water requirement of 11000 m�/ha per year according to the present study, it would be possible to irrigate another 77000 ha [*], which would bring the total to about 201800 ha. In the upper Buzi and Pungo� basins 7449 ha have already been developed or planned for irrigation [216] and another 1750 ha could be developed [*], bringing the total to 9200 ha. For the whole area in the Indian Ocean Coast this leads to an irrigation potential of 211000 ha. In the upper Save basin, water is the limiting factor, while in the upper Buzi and Pungo� basins the limiting factor is land.

In Mozambique the irrigation potential has been estimated at 128000 ha in the part situated to the north of the Limpopo basin and at 240000 ha in the part situated to the south of the Limpopo basin, giving a total of 368000 ha [159].

TABLE 80 Indian Ocean Coast: 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)
Swaziland	93220	9000	0.839	67.400
South Africa	877800	10000	8.778	688000
Zimbabwe	211000	11000	2.321	65000
Mozambique	368000	11000	4.048	41710
Sum of countries	1550020		15.986	862110
Total for Ind. Oc. Coast	1500000		15.986

Problems may arise in the area where the rivers are shared by Swaziland, South Africa and Mozambique. The irrigation potential in that area has been estimated at 93220 ha for Swaziland, 100000 ha for South Africa and 240000 ha for Mozambique. The total of 433220 ha would require 4.479 km�/year of irrigation water. The total amount of water flowing to the sea has been estimated at about 6.600 km /year.

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