GOURITZ RIVER: Topography, geology and soils

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Map of the GOURITZ River

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TOPOGRAPHY

The topography of the Gouritz water management area is characterised by flat open plains of the semi- arid Great Karoo, Little Karoo and a narrow coastal plain with its deeply incised river valleys. These three distinctly different zones are separated by the steep Swartberg, Langeberg and Outeniqua mountain ranges that lie parallel to the coast. These mountain ranges influence the climate in the region, where the northern and central portions that form part of the Great and Little Karoo are hot and dry, while the southern coastal strip has a more temperate climate with significantly higher rainfall. (Ref 4)

The topography of the water management area is characterised by the flat open plains of the Great and Klein (Little) Karoo, interrupted by steep mountain ranges orientated in an east-west direction. Consequently the water resources of the Gouritz water management area occur in three distinctly different zones, namely:

  • The semi arid Great Karoo consisting of the Gamka River catchment, to the north of the Swartberg Mountains and the Groot River catchment, to the west of the Sewe-Weeks Poort (Klein Swartberg Mountains). The southern boundary of the Groot River catchment lies along the Langeberg Mountains.  (Ref 1)

  • The Olifants River flows though an arid valley but is fed by mountain streams rising in the Swartberg Mountains to the north, the central Kammanassie Mountains and the coastal Outeniqua Mountains in the south.  (Ref 1)

  • The Coastal Belt rivers rise in the Langeberg and Outeniqua Mountains along the coast and flow in valleys deeply incised into the coastal plain. Although the management of the water resources in the many small incremental catchments do have similarities, there are specific needs within certain of them. (Ref 1)
    GEOLOGY                                    
The Klein Karoo which lies to the north of the Langeberge and is 6-8 miles wide.  The Groot and Gamka tributaries arise here.  The Groot and Gamka tributaries arise here.  This area belongs to the Bokkeveld Group and consists of sandstones and shales.  The latter crop out everywhere both on the hills and the plains.(Ref 3)
The Langeberge - this mountain range runs from east to west and belongs to the Table Mountain Group(Ref 3)
The Renosterveld lies to the south of the Langeberge.  It comprises the Uitenhage Group of thin bedded shales, red and gray mudstones, conglomerates and clays; the Witteberg Group of quartzites and the Bokkeveld Group of shales, quartzites and sandstones.(Ref 3)
The Strandveld forms the 12 -13 km coastal belt. There are shingle beaches at the Gourits mouth and the mainland is mostly sandy.  There are extensive mobile dunes rising in terraces of 100m in places.  The extensive hilly areas of the strandveld are fixed sand intersected by rocky ridges and outcrops of dune limestone.  The Coastal Belt comprises superficial deposits, recent limestones, recent blown sands and sand deposits. The dune limestone is derived from the hardened dunes and is used for building purposes.  The channel  of the river has cut through the sand and limestone down to the underlying Bokkeveld beds which are exposed.  Near the river mouth, the Table Mountain Group (sandstone and quartzites) appears as a narrow strip.  There is a large quantityu of alluvium at Elberts Kraal on the Gourits River.  On the northern boundary of the Strandveld stands the Aasvogelberg belonging to the Table Mountain Group.  (Ref 3)

Karoo sediments and doleritic intrusions; sandstones, quartzite and conglomerates of the Malmesbury Group, overlain in the valley floors by alluvial deposits.  (Ref 4)

The Great Karoo consists of flat plains and low hills formed by Karoo sediments and doleritic intrusions. Towards the south the terrain becomes mountainous consisting of sandstones, shales and tillites of the Cape Supergroup. In the Olifants River catchment, in the vicinity of Oudtshoorn, the geology consists of sandstones, quartzite and conglomerates of the Malmesbury Group, overlain in the valley floors by alluvial deposits. (Ref 1)

klein_karroo_near Oudtshoorn.jpg (87916 bytes) klein_karroo_near Oudtshoorn2.jpg (45809 bytes) klein_karroo_near Oudtshoorn3.jpg (44607 bytes) klein_karroo_near Oudtshoorn4.jpg (45446 bytes) klein_karroo_near Oudtshoorn5.jpg (42176 bytes)
klein_karroo_near Oudtshoorn7.jpg (43988 bytes) Seweweekspoort2.JPG (82529 bytes) Seweweekspoort3.JPG (63345 bytes) Seweweekspoort4.JPG (64471 bytes) Seweweekspoort5.JPG (64685 bytes)
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Seweweekspoort12.JPG (58428 bytes) Seweweekspoort13.JPG (89815 bytes) Seweweekspoort17.JPG (110608 bytes) Seweweekspoort18.JPG (47928 bytes) Seweweekspoort19.JPG (72850 bytes)
Seweweekspoort22.JPG (74023 bytes) Seweweekspoort.JPG (81946 bytes)
    SOILS                                    
  References                                      

Ref1:   Department of Water Affairs and Forestry, South Africa. 2004. Gouritz Water Management Area: Internal Strategic Perspective. Prepared by Ninham Shand (Pty) Ltd in association with Jakoet & Associates and Umvoto Africa, on behalf of the Directorate: National Water Resource Planning. DWAF Report No P WMA16/000/00/0304.

Ref3:  ESTUARIES OF THE CAPE REPORT NO. 38 Gourits (CSW 25)CSIR Research Report 437

Ref 4:  RIVERS OF THE GOURITZ WATER MANAGEMENT AREA 2007
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