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eWISA
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BLYDE:
MAIN INDEX |
ALPHABETICAL
LIST OF RIVERS |
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Map
of the BLYDE River |
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us |
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TOPOGRAPHY
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GEOLOGY
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"The geological
characteristics of the Blyde catchment consist of a relatively complex
series of lithological formations that underlie the area forming the
Drakensberg
Mountains. In the eastern
portion of the upper reaches of the catchment, the most important
features are the deep layers of dolomites of the Chuniespoort Formation,
interspersed with alternating layers of indurated shales and quartzites
of the Pretoria Series of the Transvaal Sequence.
In the western portion of this zone, the sub-catchment is
underlain by complex sequences of shales, conglomerates, silicified
sandstones and quartzites of the Transvaal Sequence.
The hard, erosion-resistant rocks forming the northward
continuation of the
Drakensberg
Mountains
rise steeply from the Mpumalanga Lowveld, forming conspicuous,
steep-sided cliffs." (Ref 2)
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"Water moving
through the deep layers of Chuniespoort dolomites in the upper parts of
the sub-catchment becomes saturated with calcium carbonate; this
precipitates out to form tufa when the water appears above ground level.
As a consequence, most of the waterfalls in the area are layered
with thick, “growing” deposits of tufa." (Ref 2)
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"In the northern
parts of the sub-catchment, downstream of the Blydepoort
Dam, crystalline gneissic and granitic rocks of the Basement Complex
underlie the catchment. These
coarse- to fine-grained, feldspar-rich rocks have been intruded by
numerous hard, fine-grained syenite “plugs” that are more
erosion-resistant; these are visible as stack-like features across the
otherwise undulating terrain in the lower parts of the sub-catchment.
In addition to the intrusive syenite formations, the basement
complex has also been intruded by a large number of dolerite dykes.
These dolerites are softer and more easily eroded than the
Basement Complex rocks and the dykes are often visible as troughs in the
landscape. These troughs
collect rainfall and act as local watercourses; this water enhances the
erosion process." (Ref 2)
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SOILS
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"The riverbed is characterized
by an abundance of big rocks, stones and pebbles. The riparian zone
alternates between narrow zones close to the stream and broad zones with
sandbanks and floodplains. The floodplains are elevated in relation to
the riverbed." (www.csir.co.za/rhp/state_of_rivers/state_of_crocsabieolif_01/olif_eco_5.05.html)
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"Soils in the
sub-catchment can be divided into four main groups:
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Moderate
to deep sandy and clay-loam soils on flat, gently-sloping and
undulating terrain overlying dolomite, limestone and sandstones in
the upper reaches of the catchment;
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Moderate
to deep sandy to clay loam soils lining long stretches of the Blyde
and Ohrigstad river valleys in their middle reaches;
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Moderate
to deep clay loam soils over much of the middle portions of the
sub-catchment (located away from the river channels), overlying the
more porous unconsolidated sedimentary and hillwash material; and
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Moderately
shallow to moderately deep, coarse-grained sandy loam to clay-rich,
fine-grained soils derived from granites and gneisses over most of
the lower reaches of the sub-catchment." (Ref 2)
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"Most of
the clayey loam soils are very suitable for irrigated agriculture when
sufficient water is provided. Virtually
all of the suitable soils are contained within the jurisdiction of
formal irrigation boards or Government Water Control Areas.
Further away from the main river channels, most of the land use
is given over to small-scale irrigation from farm dams as well as the
raising of small and large livestock (dairy and beef cattle, goats and
sheep). A wide variety of
crops are produced, ranging from intensive vegetable production to
tobacco, maize, citrus and sub-tropical fruits, sorghum and sunflowers.
Minor areas of plantation forestry (mostly Pines and Eucalyptus)
are also located in the wetter portions of the sub-catchment."
(Ref 2)
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References |
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"Ref 2" (www.mining.wits.ac.za/FinalReport-Section5.doc)
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Useful
links |
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