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

3.33 The Angwa sub-catchment
3.33.1 General description
3.33.1.1 Hydrology
This is Zones A1-A2 of Area C (ZSG, 1984). The Angwa River flows from near Chinhoyi Caves to Lake Cahora
Bassa in Mozambique (Figure 3.2). There are many wetlands in the Manyati area of the middle Angwa, Zone
A1.
3.33.1.2 Geology
See Figure 3.6 (ZGS, 1999). Magondi Supergroup gneisses and metasediments underlie most of the subcatchment.
Karoo Supergroup and Dande Formation sediments underlie the area north of the Zambezi
Escarpment. The area around Mwami, east of Karoi, is intruded by numerous pegmatites, many of which are
mined. For a more detailed description of these pegmatites, see Wiles (1961).
3.33.1.3 Pedology, agriculture and land use
Soils in the sub-catchment can be divided into four groups:
• Very shallow, gravelly soils in the area along the Zambezi Escarpment and the Manyame Range;
• Moderately shallow to moderately deep hydromorphic silty clay loams, derived from Magondi
metasediments;
• Moderately shallow, fine grained and highly micaceous sandy loams, derived from Magondi gneisses; and
• Moderately shallow sands and loamy sands, often sodic, formed from Upper Karoo and Dande sediments
(DRSS, 1979).
The lower Angwa valley (below the Zambezi Escarpment) lies within Natural Region IV: fairly low rainfall of
450mm to 650mm per annum. The middle Angwa valley (from Darwin Gorge to the Zambezi Escarpment) lies
within Natural Region III: high rainfall and deep soils. The upper Angwa valley (above Darwin Gorge) is within
Region IIa: high and reliable rainfall of up to 1000mm per annum and deep soils (ZSG, 1997; Surveyor General
and AGRITEX, 1998).
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