African Unification Front
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THE LIMPOPO BASIN
The Limpopo basin, located in South-eastern Africa, covers 1.3% of the continent and spreads over four countries. The drainage area of the Limpopo and its tributaries is approximately 384,000 sq km.
The Krokodil (Crocodile) is the uppper part of the Limpopo River and originates in the Witwatersrand, near Johannesburg in South Africa, and flows on a semicircular course first north-westwards to the border with Botswana and then turns to flow northeastwards, first on the border between South Africa and Botswana and then on the border between South Africa and Zimbabwe. It flows 1,100 miles (1,800 km) to the Indian Ocean.
Several tributaries originate in Botswana, the most important being the Shashi, which forms the border between Botswana and Zimbabwe before flowing into the Limpopo River. Entering Mozambique, the river has an average annual discharge of 4.8 km3. From its source the river flows northward to the Magaliesberg, cutting the Hartbeespoort Gap, which is the site of an irrigation dam. It then flows across the fertile Bushveld basin to open granite country, where it is joined on the left bank by the Marico River. From there it is known as the Limpopo. (The name may be Sotho meaning "river of the waterfall.")
Turning northeastward, the river forms the border for about 250 miles (400 km) between Northern Province and Botswana, receiving seasonal tributaries. After swinging eastward between Northern Province and Zimbabwe, the Limpopo receives the Shashi River and flows about 150 miles (240 km) to Mozambique, where it reaches the fall line. In this zone the river drops about 800 feet (250 metres), with most of the drop concentrated in 27 miles (43 km) of rapids, especially those at Malala, Molukwe, and Quiqueque.
Another important tributary, the Elephants River (also called the Transvaal River), originates in South Africa not far from Johannesburg and flows in north-eastwards. It flows into the Limpopo River in Mozambique. The Limpopo is unnavigable until its confluence with the Olifants River, 130 miles (209 km) from the coast. Though partially blocked by a sandbar at its outlet, the river can be entered by coastal steamers at high tide. The Limpopo is dammed about 62 miles (100 km) from its mouth near Guijį, where an agricultural settlement has been developed.
The Krokodil headwaters at Hartbeespoort Dam have a mean annual discharge of 124,000 acre-feet (152,954,000 cubic metres), with maximum flow in February and minimum in August. The Limpopo's lower and middle courses reflect climatic changes, drying to a series of pools in the winter months and reaching flood proportions in the summer.
The Mozambican part of the basin area is estimated to contribute only 10% of the total mean annual runoff of the river. The Limpopo River, which was initially a perennial river in Mozambique, can actually fall dry for up to a period of eight months per year, mainly due to abstractions in the upper catchment area.
The quantity of water produced in the Limpopo Basin within Botswana is estimated at about 0.6 km3/year. The maximum irrigation potential is estimated at 15,208 ha, of which about 10,000 ha would need important works for water development and storage. Moreover, as several major towns of Botswana are located in this area, including the capital Gabarone at the Notwane tributary, water problems may arise. The irrigation potential for the region is 5000 ha.
Surface water resources produced in the basin area in Zimbabwe are estimated at 0.54 km3/year, of which 0.41 km3 drains to the Limpopo River at the border between Zimbabwe and South Africa and 0.13 km3 enters Mozambique before flowing into the Limpopo River. After deducting the water already committed for domestic, industrial, mining and irrigation use and the water which can not he developed, about 0.076 km3/year of water is considered as being potentially available for irrigation development. At present 3,992 ha have been developed or planned for irrigation. Land still suitable for irrigation is about 70,000 ha, but water constraints limit the area to 6900 ha. This brings the total irrigation potential to about 10,900 ha.
For South Africa the water resources per sub-basin, it is estimated that by 2010 in the whole of South Africa 15 to 16 km3/year of water will be available for agricultural purposes. At present 198,000 ha are already irrigated, using less than 10,000 m3/ha per year.
The irrigation potential for Mozambique in the Limpopo basin has been estimated at 148,000 ha.
In view of the fact that the Limpopo River in Mozambique can already fall dry during eight months of the year, the above potential has to be considered as an upper limit, requiring important storage works and good cooperation between the basin countries.
Should South Africa use 12,000 m3/ha per year, it would already irrigate more than its potential. Botswana and Zimbabwe have higher irrigation water requirements, which means that in such a case the already small-potential of these countries would also have to be reduced.
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