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

Air temperatures across the Zambezi basin show a marked seasonal cycle, with hottest temperatures recorded
during the early Austral Summer months and lowest temperatures during the cool, dry winter months. Rainfalls
are also highly seasonal, falling predominantly as intense convective thunderstorms during the warmer summer
months (Chenje, 2000). Rainfalls vary from as little as 450 mm per annum in parts of the lower Zambezi valley
to over 2,000 mm per annum on the Mulanje Plateau and the Livingstone Mountains to the north of Malawi. The
“average” position of the ITCZ is located across the central and northern portions of Zambia; these areas
regularly receive rainfalls in excess of 1,500 mm each year. A sketch map showing the distribution of mean
annual rainfall over the Zambezi basin is shown in Figure 3.1. This figure also shows the main tributaries of the
Zambezi.
Evaporation rates across the Zambezi basin are both high and variable, ranging from some 2.4 metres per
annum in the south-western areas of Botswana, Namibia and Zimbabwe, to some 1.65 metres in the cooler,
mountainous regions to the north of Lake Malawi. In view of these evaporation rates, and the quantity of rainfall
received each year, several areas of the Zambezi show clear evidence of the dominance of physical weathering
processes (Weinert N values greater than 5.0). These areas are located in the southwestern portion of the
basin and along the middle Zambezi valley. Virtually all of the rest of the Zambezi 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).
3.1.3 Population and land use patterns
The total population of the Zambezi basin is approximately 30.8 Million, with Malawi, Mozambique, Zambia and
Zimbabwe having the highest proportion of the basin population (Table 3.2). The Zambezi basin covers over
half of the area of Malawi, Zambia and Zimbabwe, containing the breadbasket districts of these three countries,
most of the largest cities and towns and most of the largest mines. As such, the basin includes the economic
heartland of these three countries.
All Zambezi basin states have skewed population distributions, and experience large-scale migration from rural
areas to urban settlements. In addition to this pattern of urbanization, several countries (especially Malawi and
Zambia) also house several million refugees who have escaped from various civil wars in Angola, Burundi,
Democratic Republic of Congo, Mozambique and Rwanda. These unfortunate people place a heavy additional
burden on the economies and fragile natural resources available in these two countries.
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