OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

are also highly seasonal, falling predominantly as intense convective thunderstorms during the warmer summer
months. Rainfalls vary from as little as 400 mm per annum in the central parts of the Limpopo valley to over
1,000 mm per annum on the Drakensberg Mountains and close to the mouth of the Limpopo River at Xai-Xai. A
sketch map showing the distribution of mean annual rainfall over the Limpopo basin is shown in Figure 4.1.
This figure also shows the main tributaries of the Limpopo River.
Evaporation rates across the Limpopo basin are both high and variable, ranging from some 3.1 metres per
annum in the western and central areas of the basin to some 1.7 metres in the cooler, mountainous regions in
the southeastern portion of the basin. In view of these evaporation rates, and the quantity of rainfall received
each year, several areas of the Limpopo basin show clear evidence of the dominance of physical weathering
processes (Weinert N values greater than 5.0). These areas are located in the western and central portions of
the basin and along the middle Limpopo valley. Virtually all of the rest of the Limpopo basin is subject to
chemical weathering processes, either seasonally (Weinert N values below 4.0) or continually (Weinert N values
below 2.0) (Weinert, 1964).
4.1.3 Population and land use patterns
The total population of the Limpopo basin is approximately 10.5 Million, with almost 60% of Botswana’s
population located within the basin (Table 4.2). The Limpopo basin also contains a large proportion of the
population comprising South Africa’s Gauteng Province, as well as the population of the Northern Province, and
almost all of the agricultural areas, towns and cities, mines and power stations of these two provinces. As a
result, the basin includes most of the critically important economic and energy heartland of South Africa.
Table 4.2: Population statistics for the four SADC states comprising the Limpopo basin (excluding the Olifants
sub-basin, which is dealt with in Section 5). [Data obtained from SARDC (1996), Basson et al. (1997), Chenje
(2000)].
Country
Total
Population of
Country
(Millions)
Country
Population in
Basin
(Millions)
ccxii
Proportion of
Country
Population
(%)
Proportion of
Basin
Population
(%)
Botswana 1.639 0.975 59.5 9.3
South Africa 43.421 7.950 18.3 76.1
Mozambique 19.980 1.150 5.8 11.0
Zimbabwe 13.109 0.375 3.0 3.6
Totals: 78.149 10.450 13.4 100.0
In Botswana, the Limpopo catchment supports several important towns and the capital City of Gaborone. The
South African sector of the Limpopo Catchment supports several large and medium-sized towns as well as
numerous smaller communities. Pietersburg, capital of the Northern Province, is also located here. In addition,