STEELPOORT RIVER: Topography, geology and soils

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Map of the STEELPOORT River

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TOPOGRAPHY
"The underlying geological formations beneath the Steelpoort sub-catchment consist predominantly of basic rocks of the Bushveld Igneous Complex, consisting predominantly of magnetite-rich gabbros, norites, anorthosites, pyroxenites and gabbroic rocks of the Rustenburg Layered Suite (RLS).  These rocks form the base of the relatively flat-bottomed valley areas as well as forming the watershed marked by the steep-sided, more mountainous or hilly terrain to the east and west of the Steelpoort River ."    (Ref 2)
"The mountainous area located to the northeast of the sub-catchment (close to the confluence of the Steelpoort and Olifants rivers) consists predominantly of erosion-resistant quartzites shales and silicified shales of the Transvaal Sequence.  These rocks form steep-sided hills and cliffs with little surface soil.

The Steelpoort Valley itself is a steep-sided valley that trends in a predominantly northeasterly direction as a result of the Steelpoort Fault.  This regional structure appears to have been exploited by the Steelpoort River during its evolution.  The valley floor is covered with extensive, deep deposits of colluvium (hillwash), with more recent (Quaternary) alluvial deposits located on the flood terraces on either side of the Steelpoort River ."    (Ref 2)

    GEOLOGY                                    
    SOILS                                    
"The river has deep alluvial sands and silt deposits. In some areas the river forms secondary channels, floodplains and woody islands."  ((www.csir.co.za/rhp/state_of_rivers/state_of_crocsabieolif_01/olif_eco_4.03.html))
Soils in the sub-catchment can be divided into three main groups:

  • Moderate to deep, stony sandy-clay loam soils on the foot slopes, as well as the sloping and undulating terrain in the upper reaches of the sub-catchment;

  • Shallow to moderately deep clayey loam soils lining the valley bottoms in the middle reaches of the sub-catchment; and

  • Shallow to moderately deep fine to coarse sandy alluvial soils lining flood terraces on either side of the river channels, particularly in the central and lower reaches of the sub-catchment.    (Ref 2)

"Most of the clayey loam soils in the upper and central parts of the sub-catchment are very suitable for cultivation and extensive rain-fed and irrigation agriculture is practiced in these regions.  Water is pumped either directly from the Steelpoort River or from small storage dams on tributary streams for small-scale irrigation.  Minor use is made of borehole water for irrigation, especially in the central and lower reaches, due to problems with vanadium contamination and possible toxicity."  (Ref 2)
  References                                      

"Ref 2" (www.mining.wits.ac.za/FinalReport-Section5.doc)
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