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The River Basin
Climate and Weather
 Principles of Hydrology
Hydrology of Southern Africa
 SADC Hydrogeological Map
 Hydrology of the Kunene Basin
Water Quality
Ecology & Biodiversity



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Hydrology of Southern Africa  

The hydrology of southern Africa can be considered on several levels, but the most fundamental level is to examine the prcipitation and the distribution of rivers.


Southern Africa experiences variable precipitation levels ranging from low (less than 250 mm/yr) over large areas of the region, to relatively high (more than 1 200 mm/yr), which tends to be concentrated in the north of the SADC with some smaller areas along the south-east coast. Most rain falls in the summer months (December to March) with the exception of the Western Cape of South Africa, which has a temperate climate. Rainfall is highly variable in distribution and intensity, particularly in the drier regions (Pallet et al. 1997). When rain does fall it is often episodic, arriving in short intense downpours during warm weather. Rain falling in intense downpours often runs off into river channels as it falls faster than can be absorbed into the soil.

The map below shows the average rainfall distribution across southern Africa. This map shows average values, and thus does not highlight temporal variation or local spatial variation of rainfall.

Regional distribution of precipitation.
Source: FAO 2000
( click to enlarge )

The table below summarises the rainfall and evaporation statistics for the region, including rainfall range.

Rainfall and Evaporation Statistics for (Selected) SADC Countries

Country Rainfall range Average Rainfall Potential evapotranspiration range

Total surface

mm mm km³ mm mm km³
Angola 25-1600 800 997 1300-2600 104 130.0
Botswana 250-650 400 233 2600-3700 0.6 0.35
Lesotho 500-2000 700 21 1800-2100 136 4.13
Malawi 700-2800 1000 119 1800-2000 60 7.06
Mozambique 350-2000 1100 879 1100-2000 275 220.0
Namibia 10-700 250 206 2600-3700 1.5 1.24
South Africa 50-3000 500 612 1100-3000 39 47.45
Swaziland 500-1500 800 14 2000-2200 111 1.94
Tanzania 300-1600 750 709 1100-2000 78 74.0
Zambia 700-1200 800 602 2000-2500 133 100.0
Zimbabwe 350-1000 700 273 2000-2600 34 13.1



Source: Pallet et al. (1997)

Water losses from evaporation and evapotranspiration are extremely high in southern Africa, with only a small percentage of rainfall reaching aquifers through groundwater recharge or surface water through run-off (Pallet et al.)The map below shows the distribution of evapotranspiration across the region.

Regional distribution of evapotranspiration.
Source: FAO 2000
( click to enlarge )

Surface Water

The surface resources are distributed fairly unevenly across the southern African region, with Namibia and most of Botswana in particular have very few surface water resources. Many of the water channels across the region, especially those in areas of low rainfall, high temperatures and high rates of evaporation are non-perennial, only flow after the intense rainfall events that characterise precipitation in the region.

Surface water flows are also subject to human intervention, mainly in terms of streamflow reduction for irrigation, domestic and urban supply.  Dams and other impoundments stop streamflow and in many cases fundamentally alter river basin hydrology. In 2000 there was an estimated 746 dams in the SADC region (FAO 2000). This number is likely to have increased substantially.

Distribution of regional surface water drainage.
Source: FAO 2000
( click to enlarge )


Due to the limited availability of surface water resources, groundwater is critical to integrated water resources management, particularly in rural areas not close to larger rivers or urban water supply networks.

The map below, developed by the German Geological Survey and UNESCO (WHYMAP 2008), describes groundwater resources in terms of:

  • Major groundwater basins;
  • Areas of complex hydrogeological structure; and
  • Areas with local and shallow aquifers.

Groundwater recharge potential, related to climatic conditions such as average temperatures and evapotranspiration, and geological factors such as porosity and infiltration rates, is relatively low across much of the southern African region, improving to the north, due mostly to increased precipitation.

Regional groundwater resources and recharge.
Source: WHYMAP 2008
( click to enlarge )




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Video Interviews about the integrated and transboundary management of the Kunene River basin

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