LIMPOPO RIVER: Topography, geology and soils

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TOPOGRAPHY
The Crocodile (west)/Marico Water Management Area (Marico): 
The topography of the area is generally very flat with undulating hills in the lower reaches of the Marico River. (Ref.4)
The Crocodile (west)/Marico Water Management Area (Crocodile):
The Crocodile River and some of its main tributaries rise in the south of the catchment in the Witwatersrand topographical feature at an altitude close to 2000 m. This feature in the southern part of the catchment may be described as gently rolling hills on the highveld plateau. The rivers wind their way through the Daspoort Ridge to the Magaliesburg mountain range at the Hartbeespoort Dam where the altitude is around 1200 m. The Crocodile River then meanders through a reasonably flat weathered volcanic landscape, past the extinct Pilansberg volcano, and through the Thabazimbi mountains down to its confluence with the Groot Marico where it becomes the Limpopo River (altitude approximately 900 m). (Ref.5)
The Limpopo Water Management Area:
While the topography of the Limpopo catchment in north and north west is mostly flat, the Waterberg mountain in the Limpopo Province forms an escarpment along the south with altitudes in excess of 1 800m. From here the area slopes gradually down to the Limpopo River, hence the rivers in the northern part of the Limpopo Province drain in a northerly direction. Ref.1

The topography of the catchment in the north and north west  is characterised by mountain ranges surrounded by vary flat areas which offer very few suitable dams sites. The major mountain ranges in the are: (Ref.1)

The Waterberg in the south and east, with an altitude of over 1 800m. The Waterberg also forms an impressive escarpment between the Lephalala and Mogalakwena River catchments as well as between the Mokolo and Mogalakwena River catchments.
The Soutpansberg range, with an altitude of over 1 700 m, intrudes into the Sand River catchment extending about 50 km west of Makhado and forms the upper reaches of the Nzhelele and Nwanedi River catchments.
The Blouberg mountain, a free-standing massif of quartsite, is situated in the Mogalakwena River catchment and is the highest peak in the Limpopo WMA, at over 2 000 m.
The Buffelshoek mountain range, with an altitude of over 2 000m in places, extends east from Mokopane.
There are numerous free-standing granite massifs in the Mogalakwena River catchment, the largest of which has an altitude of over 1 700m.
The Luvuvhu/Letaba Water Management Area:
The topography in the north-east (Luvuvhu/Letaba) varies from high mountains through low mountains and foothills to the low lying plains in the east. The mountainous zone or Great Escarpment includes the northern portion of the Drakensberg mountain range and the eastern Southpansberg extend to the western  characteristic wide plains of the Lowveld. The highest peaks have an elevation of more than 2 000 m above mean sea level (msl). This area is deeply incised by the major tributaries draining the area.  The predominant topographical feature in the Luvuvhu Basin is the Soutpansberg mountain range. Its highest points and steepest slopes are situated in the upper portion of the Luvuvhu catchment. This has a profound effect on the hydrology of the rest of the catchment with significant higher rainfall a result of the topographic influence.Ref.2.

High mountains occur along the western boundary of the Letaba catchment, with foothills and undulating plains over the remainder of the area. Ref.2.

The Olifants Water Management Area:
The topography in the Olifantscatchment is characterized in the southern part of the catchment by rolling gently sloped hills, before the river cuts through the Drakensberg to enter the relatively featureless Lowveld region. Largely attributable to the topography, distinct differences in climate occur. The climate varies from cool in the southern Highveld region of the water management area through temperate in the central parts to sub-tropical east of the escarpment. The rainfall is strongly seasonal occurring mainly in summer. The mean annual rainfall falls in the range 500 mm in the Lowveld region, reaching 1000 mm in the mountains and reducing to 700 mm in the South in the Mpumalanga Highveld region of the WMA. The potential evaporation is well in excess of the rainfall. (Ref 1)
    GEOLOGY                                    
The Crocodile (west)/Marico Water Management Area (Marico): 
In the Upper catchment of the Groot Marico as well as the Upper Ngotwane catchment, the landscape is generally flat to gently rolling due to the Malmani dolomites. The dolomite is intruded by numerous dolerite dykes that have effectively sub-divided the dolomite into a series of compartments, which may or may not be hydraulically linked. Groundwater is widespread, especially in chert rich horizons and karst zones where borehole yields greater than 5l/s are common, and yields of 20l/s are feasible. The NE area are underlain by sandstone, quartzite, shale, diabase and andesite of the Pretoria Group. (Ref.4)
The Crocodile (west)/Marico Water Management Area (Crocodile):
The major feature geological feature of this catchment is the large area of volcanic intrusive rock (north of the Magaliesburg to Thabazimbi) referred to as the Bushveld Igneous Complex. Formations in this complex are extremely rich in minerals, which has led to large-scale exploitation of the platina group of metals in this area. Soil types in this area may be broadly classified as moderate to deep clayey loams which are well utilised for agricultural crops and which also allow a relatively high percentage of runoff of water. Dolomitic rock is found in a band running east-west between Rietvlei Dam and Mogale City (formerly Krugersdorp). These dolomitic compartments tend to be chert-rich, with consequent high water storage capacity. Dewatering of these compartments has led to sinkholes in the past. Some of the gold-bearing seams of the Witwatersrand Ridge in the south fall within the upper catchment but only a few goldmines still operate here. Soils in this higher and undulating southern part of the catchment are broadly classified as sandy loam, which are easily susceptible to erosion. The balance of catchment consists of sedimentary rock, with the quartsitic Magaliesberg Mountain Range being the prominent feature. (Ref.5)
The Limpopo Water Management Area:
"The Limpopo Water Management Area is underlain by a wide variety of different lithologies. In the north, the Limpopo Mobile Belt occurs as well as the Soutpansberg Group rocks, of which the Soutpansberg Range and Blouberg mountains form a part. The western and southern portion of the WMA consists of Waterberg sandstone which overlies Nebo Granite and the Lebowa Granite Suite which form the northern slope of the Bushveld complex. This is very important for mining since the Bushveld Complex is rich in minerals, especially Platinum, and there has been rapid development of mines in the Limpopo WMA recently. The central part of the WMA is underlain by the Houtrivier and Mashashane gneisses which have been intruded by younger granite plutons; for example, the Mashashane and Matlala granites."  REF 1.
The Luvuvhu/Letaba Water Management Area:
The geology is varied and complex and consists mainly of sedimentary rocks in the north and metamorphic and igneous rocks in the south. High quality coal deposits are found near Tshikondeni and in the northern part of the Kruger National Park, whilst the eastern limb of the mineral rich Bushveld Igneous Complex touches on the southern parts of the water management area. With the exception of sandy aquifers in the Limpopo River Valley, the formation is of relatively low water-bearing capacity. (Ref.2)
The Olifants Water Management Area:
The geology in the Olifants catchment consists mainly of hard rock formations, with the occurrence of the Bushveld Igneous Complex as the most prominent feature. The eastern limb of this formation cuts through the northern part of the water management area. Rich coal deposits occur in the Upper Olifants Sub-area in the vicinity of Witbank and Middelburg. A large dolomitic intrusion extends along the Blyde River, curving westwards along the northern extremity of the water management area.(Ref.3)
    SOILS                                    
The Crocodile (west)/Marico Water Management Area (Marico): 
Moderate to deep clay loam soils occur in most of the Upper Molopo catchment with moderate to deep sandy soils in the lower reaches of the D41A catchment. The moderate to deep clay loam soils are not the ideal soils for irrigation farming because although they have a reasonably high water holding capacity they are not readily penetrable by water. (Ref.4)

Moderate to deep clay loam soils with undulating topography occurs in the Marico (with the exception of the lower Marico) and Upper Ngotwane catchments. These soils are also not very suitable for irrigation farming, also due to their low permeability. Overgrazing in some portions of the catchment results is excessive soil erosion and loss of land cover. This has an impact on groundwater recharge. Irrigation farming is generally practised along the Groot Marico and its tributaries. (Ref.4)

Moderate to deep sandy loam soils in general flat terrain occur in the lower Marico. These soils are ideal for irrigation farming because they provide a good balance between the ability to convey water and ability to retain water. This is the area where most of the irrigation is taking place (Ref.4)

The Crocodile (west)/Marico Water Management Area (Crocodile):
Soils in the northern part of the catchment are classified as sandy loams. (Ref.5)
The Limpopo Water Management Area:
"The soils in the Limpopo WMA can be summarised as deep sandy soil in the north, moderate to deep sandy loam in the central regions, and a mixture of sandy loam and clayey soil in the south. In the Soutpansberg area, the soil type is clayey loam. The deep soils of the Limpopo WMA are generally well-suited to agriculture, but the lack of surface runoff has been the limiting factor in agricultural development." Ref 1
The Luvuvhu/Letaba Water Management Area:
A wide spectrum of soils occur in the water management area, with sandy soils most common.(Ref.2)
The Olifants Water Management Area:
"Soils in this ecoregion are highly erodible. The situation is worsened by intensive cultivation and grazing, which have caused general degradation of land cover."  (www.csir.co.za/rhp/state_of_rivers/state_of_crocsabieolif_01/olif_eco.htm)
  References                                      

Ref 1: Department of Water Affairs and Forestry, South Africa. 2004. Internal Strategic Perspective: Limpopo Water Management Area : Prepared by Goba Moahloli Keeve Steyn (Pty) Ltd, in association with Tlou & Matji (Pty) Ltd and Golder Associates (Pty) Ltd. on behalf of the Directorate: National Water Resource Planning. Report No. P WMA 01/000/00/0304.

Ref.2. Department of Water Affairs and Forestry, South Africa. 2004. Luvuvhu/Letaba Water Management Area: Internal Strategic Perspective. Prepared by Goba Moahloli Keeve Steyn (Pty) Ltd in association with Tlou and Matji, Golder Associates Africa and BKS on behalf of the Directorate: National Water Resource Planning. DWAF Report No. P WMA 02/000/00/0304. 

Ref.3. Department of Water Affairs and Forestry, South Africa. 2004. Olifants Water Management Area: Internal Strategic Perspective. Prepared by GMKS, Tlou and Matji and WMB on behalf of the Directorate: National Water Resource Planning. DWAF Report No P WMA 04/000/00/0304 .

Ref.4. Department of Water Affairs and Forestry, South Africa. 2004. Crocodile (West) and Marico Water Management Area: Internal Strategic Perspective of the Marico-Upper Molopo & Upper Ngotwane catchments. Prepared by Goba Moahloli Keeve Steyn in association with Golder and Associates and Tlou and Matji (Pty) Ltd. DWAF Report No. P WMA 03/000/00/0404

Ref.5. Department of Water Affairs and Forestry, South Africa. 2004. Crocodile River (West) and Marico Water Management Area: Internal Strategic Perspective of the Crocodile River (West) catchment : Prepared by Goba Moahloli Keeve Steyn (Pty) Ltd, Tlou & Matji (Pty) Ltd and Golder Associates (Pty) Ltd, on behalf of the Directorate: National Water Resource Planning. DWAF Report No. 03/000/00/0303.

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