Kunene River in KaokolandWith an areal of approximately 824.000 square km, Namibia is more than tripple the size of Great Britain. The north-to-south length of the country is 1500 km, while the east-to-west width is around 600 kilometres in the south and 1100 kilometres in the north. The population density is very low (1,8 million people), amounting to 2,2 inhabitants per sqkm. The main reason for this being the harsh desert and semi-desert conditions and the resultant scarcity of surface water. With the exception of the border rivers - Orange in the south and Kunene, Okavango and Zambesi in the north - there are only dry rivers in Namibia.They are called "Riviere" and only flow periodically during the rainy season, sometimes just for a few days or even hours.
Namibia can be divided into four major geographical segments. In the west stretches the Namib Desert with hardly any vegetation. It reaches from the north of South Africa up to Angola. The desert belt has a width of about 100 kms in the south and 1100 kms in the north, gets up to 600 metres high and is characterised by mighty expanses of sand dunes in its central part. In the north and the south it has predominantly gravel fields. Towards the inland, the desert belt is followed by the "Escarpment", a mountain wall of up to 2000 metres. Namibia's highest mountain is the Brandberg with a height of 2579 m.
The Escarpment changes into the Central Plateau which slowly descends towards the east. The heights of the central highland vary between 1100m and 1700m. The majority of the Namibian towns and villages lie on this plateau, like the capital of Windhoek at 1654 metres above sea-level. Further to the east lies the Kalahari Basin, also part of the plateau, which reaches heights of 1000m in places. It is characterised by wide sandy plains and long-dunes with scarce vegetation. Another distinct geographical area, is the north-east in the relatively rainy Kavango and Caprivi region. It is flat and covered with dense bushveld.
Simply put, average rainfall increases from the south-west to the north-east. The annual amounts vary between 50 mm in the Namib and 700 mm in the Caprivi. In years of drought, like 1991 to 1993, they can even be much lower than that.
Rain mostly comes from the north-east between December and February, when humid, unstable air masses approach from the tropical part of Africa and reach Botswana and Namibia, causing strong thunderstorms with torrential rains. Most of the rainwater evaporates immediately or is channelled away as sheet flow without being absorbed by the vegetation. However, due to water-impermeable layers of clay and stone, the groundwater is collected and is eventually used by the surrounding settlements and farms.
Part of the annual rainfall is collected in dams, the biggest of them being Hardap Dam near Mariental with a capacity of 300 million cubic metres. The water supply remains, on account of the growing population, a major problem for Namibia. There are, for example, plans to build a pipeline from the Okavango to Windhoek, but Botswana fears changes in the ecology of the Okavango Delta and opposes the project.