Thukela Situational Assessment WAI - DWS … Thukela River is a principal river of KwaZulu-Natal...

Thukela Situational Assessment WAI

Prepared by AJ Wilson 24 April 2001

5. Catchment Characteristics

5.1 Physical Characteristics

The physical characteristics of the Thukela Water Management Area are displayed in figures Figure 10 and Figure 11 on pages 26 and 27.

The Thukela River is a principal river of KwaZulu-Natal province, South Africa and is ranked as the largest river by volume in the country (www.britannica.com). Historically, the Thukela (in Zulu, Thukela means "something that startles") marked the southern boundary of Zululand. The total drainage basin of more than 29,000 square km includes most of western KwaZulu-Natal. It rises as a stream on the 3,050-metre high Mont-aux-Sources plateau near the merger point of the Lesotho-Free State province borders. Its upper course, which lies within Royal Natal National Park in the Northern Drakensberg, hurtles down a series of waterfalls as it drops a total of 948 m. The river then cuts through the Thukela Gorge at the foot of the escarpment (about 1,500 m above sea level), is quickly joined by many tributaries, passes through the Ladysmith Basin, and, below Colenso, becomes narrow and deep. At Jameson's Drift it enters the wide, open Thukela Trough, at the eastern end of which it cuts deeply through a great block of sandstone to issue onto the coastal plain. Estimates of the Mean Annual Runoff (MAR) are between 3850 and 4400 MCM per annum which is only 17% of the precipitation that falls on the catchment.

The Thukela ends its course of 502 km at the Indian Ocean, about 84 km north of Durban, its mouth obstructed in times of normal flow by a sandbar. The river is navigable only in the lagoon formed behind the sandbar. Deposits from the river form a large oceanic sand bank some kilometers from the shore that is home to significant prawn production.

The major tributary of the Thukela is the Buffalo. Other smaller but important tributaries include the Bushman’s, Mooi, Little Thukela, Klip, Sundays and Blood Rivers.

A great variety of soils are found in the Thukela catchment, the bulk of them being highly erodable Mispah and Glenrosa soils. Differences in climate are responsible for the occurrence of soils which have developed in widely diverging directions. The soils in the catchment can thus be classified according to the ecological regions in which they are found. These are the Highlands and Midlands Mist Belt, the Interior Basin, the Valley Region and the Coast Region (see map). The narrow valleys and scanty alluvial deposits restrict irrigation in a large part of the Thukela catchment, although localized areas such as that at Muden are well irrigated.



Woodstock and Spioenkop Dams regulate flow in the upper reaches of the river and act as a supply to the Thukela/Vaal pumping scheme that supplies water to the more highly developed Vaal basin. Plans are afoot to develop the water resources further by constructing more dams in the upper/middle reaches of the Thukela and its tributaries (see section 7.2).



Figure 10 : Thukela WMA Rivers and Catchments

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Buffal o

Blood

Nottingham Road

Mooi River

Estcourt

Giants Castle

Champagne Castle

Fort Mistake

ElandslaagteBesters

LadysmithGeluksburgOliviershoek

Royal Natal N P

Bergville

Cathedral Peak

WintertonColenso

Frere

Dannhauser

Dundee

Wasbank

Pomeroy

Tugela Ferry

Weenen

Muden Kranskop

Jamesons Drift

Utrecht

GroenvleiCharlestown

Newcastle

Mooi RiverTugela River

Buffels River

Major CatchmentsDamsAll_rivers_thukela.shpRiversMajor Catchments - 1

c Towns

10 0 10 20 Kilometers

PHYSICAL PROPERTIES



Figure 11 : Thukela WMA Physical Characteristics

Mooi River

Buffels River

Major Soil FormsCartrefHuttonKroonstd/EsLonglandMagwa/IaMispah/GsPinedene/Kd


SOILS

Mooi River

Buffels River

Sediment Yield (tons/ha/annum)0 - 2500025000 - 5000050000 - 7500075000 - 100000> 100000


POTENTIONAL SOIL EROSION

Mooi River

Buffels River

Slope (in Degrees)0 - 0.10.1 - 0.30.3 - 0.60.6 - 11 - 1.6


SLOPE

Mooi River

Buffels River

GeologyBasement Granite & gneissDoleriteDrakensberg FormationDwyka TilliteMuziNatal Group SandstoneNatal Mobile Belt & Pongola GroupPietermaritzburg ShaleVryheid Sandstone


GEOLOGY



5.2 Land Use

The Land use figure attached shows that this WMA includes the urban settlements of Ladysmith, Newcastle, Estcourt, and Mandini. A number of minor urban settlements are spread inland, including Dundee, Mooi River, Colenso, Winterton, Glencoe & Utrecht. All the remaining smaller settlements are largely farming cooperative areas. There are many rural settlements in this WMA, and some are densely populated, especially in the areas around Ladysmith and Newcastle.

There is some heavy industry in the urban areas of Newcastle and Dundee as well as a few bulk users around Estcourt and Ladysmith in the west and Mandini on the coast. Coal mining concerns can be found in the northern parts of this WMA. There are two mothballed Power stations (Colenso & Ngagane) in this WMA.

The majority of land is used for agriculture with areas of grassland. There is a small amount of forestry in this WMA that can be found in the southern and eastern areas. The agriculture includes large areas of beef and dairy pastures, some sugar cane near the coast and around Weenen (both dry land and irrigated), vegetables and nuts and there is some citrus farming on the coast near Mandini. The majority of irrigation is carried out using sprinkler irrigation systems, but center pivot irrigation is also used in the western areas (especially around the Thukela River).

There are some game reserves and nature parks in this WMA (see section 5.3). The largest of these is the Drakensberg Reserve area.



Figure 12 : Thukela Land Use

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Utrecht

Newcastle

Dundee

Glencoe

Ladysmith

Bergville

WintertonColenso

Weenen

Estcourt

Mooirivier

Mandini

Tugela

Mooi

Buffels

Klip

Bloed

Sundays

Slang

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Nadi

Njes

uthi

Bloukra

ns

Sand

Ngogo

Wasban k

Ncandu

Mpisi

Harts

Loza

Toleni

Ifidi

Ng aga ne

Klein - Mooi

Dwars

Sandspruit

Boe

sman

s

Sampofu

Mamba

Ste

rksp

rui t

Gubazi

Mzinyashana

Nembe

Ngc

aza

Ka als pr uit

Buffelsriviv ier

B ats

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Venterspruit

Mlambo

nja

Mbabane

Tatana

Nxwaye

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Mhlwane

Um

ngwenya

Dorin

gspr

ui t

Dorpspruit

Umnlang

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Mangeni

Mazabeko

Sithene

Ster

kst ro

om

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nyam

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mb e

L in d

e que

spru

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Mhl

onya

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Totololo

Kweeks pr uit

Ngxobongo

Mfongosi

Mtontw

anes

Mamdleni

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bidw

ana

Mp and w

en i

Man

yan e

Nhlanya

nga

Isikhehlenga

Re nsb urgs prui t

T hon

yela

na

Wasbankspruit

Eers

telin

gspr

uit

Little Tugela

Dewdrop Stream

Umdumbeni

Mi dd el sp ru it

Braamhoeksprui t

Ngagane

Buffels

Moo

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Ng ogo

Sa nd spru it

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dsp r

u it

Lesotho

Free State

KwaZulu-Natal

UPPER VAAL WMA

USUTU TO MHLATHUZE WMA

THUKELA WMA

MVOTI TO UMZIMKULU WMA

Woodstock Dam

Chelmsford Dam

Spioenkopdam

Wagendriftdam

Driel Dam

Kilburn Dam

Craigieburn Dam

Bell Park Dam

dam

Amcor Dam

Indian Ocean

Swazila

WMA Boundaries

Towns#SInternational Boundaries

Rivers

Dams

Secondary Catchment

Nature Reserve Boundaries

Provincial Boundaries

Source: CWSS Mapping 1999

Land use

Thicket Bushland

Water Bodies

Wetlands

Irrigated

Sugar Cane

Grassland

Mines

Dryland Cropping

Forest

Game Parks

Urban areas

LAND USETHUKELA WMA


SCALE: 1: 1 000 000

N

Republic of South Africa Dept. of Water Affairs and Forestry,

Directorate: Water Resources Planning

Town nameIxopo



5.3 The Natural Environment

The characteristics of the natural environment in the Thukela Water Management Area are displayed in Figure 13 on page 33.

The coastline near the Thukela River is a continuation of the long, unprotected sandy beaches further north. The most productive estuarine location, depending on the shifting sandbank at the mouth, is the area around the mouth on the southern side. The river mouth and the area a couple of kilometers out to sea are often discoloured creating conditions favourable for kob and sharks. The fish which may be caught in the vicinity of the river mouth are; large kob, garrick and shad during winter. During summer, large sharks, including the blackfin and ragged tooth and flatfish make up the catches (TRPC, 1967)

The Blood River vlei ca 6000 ha in extent, is situated in the upper Thukela catchment. The wetland provides a variety of habitats including permanently wet reed marsh, temporarily wet grasslands, seepage slope areas and several oxbow “lakes” of various depths and water regimes (WRC, 1994).

The characteristic vegetation of the Drakensberg escarpment is Themeda-Festuca alpine veld. This is restricted to the high ground bounding the catchment. The vegetation of most of the catchments of the upper Bushmans and Mooi rivers and of small areas of the upper margins of the Thukela, Venterspruit and Sand spruit, as well as the Sundays rivers on the plains, is Highland Sourveld and Dohne Sourveld. Some of the higher areas in the lower Buffalo and Insuzi river catchments are similar. The vegetation of most of the remaining areas is Southern Tall grassveld. Most of the upper part of the Buffalo river basin is somewhat different and has a perimeter of tall grassveld on high ground surrounding the main valley where the vegetation is Sour Sandveld.

The vegetation of the more broken, hilly and drier catchments of the lower-Thukela, Klip, Sundays, Bushmans, Mooi and Buffalo rivers is Dry Thorn or Valley Bushveld. Ngongoni Bushveld occurs in small areas on high ground in the lower river below Ngobevu and Ngongoni veld of the Natal mist belt occurs on the heights of Kranskop. A small area of Coastal Forest and Thornveld is found on the sandy coastal soils where the rainfall is higher. Most of the rather narrow coastal belt is used for the cultivation of sugar cane (Acocks, 1953).



There are numerous protected areas in the uThukela Water Management Area as outlined in table 4 below (State of the Environment, 1998);

Table 4: Nature Reserves in the Thukela WMA

Nature Reserve Area (ha)

Year established

Chelmsford dam 6845 1975

Moor Park 264 1967

Ncandu 1875 1925

Spioenkop 7283 1975

Thukela Drift 41 1973

Wagendrift 764 1973

Weenen 4183 1975

Cathedral Peak State Forest (partly within the catchment)

32246 1927

Giants Castle Game Reserve (partly within the catchment)

34638 1903

Royal Natal National Park 8094 1916



Mapping of the extent of the alien infestation has been carried out for the following quaternary catchments for the Thukela CMA area; V11A, V11B, V11C, V11D, V11E, V11F, V11J, V11K and V11L. Coverage reveals that the presence of weed species is a significant problem in these catchments (Abeeda Kadir, DWAF, personal comm.)

Invasive alien plants occupy about 11% of the Thukela catchment with 9% of the area described as totally invaded and 2% as condensed invasion. Solanum mauritianum is the most common species in these areas, while Acacia dealbata and Acacia mearnsii are noted for being widespread. Chromolaena is also widespread and common to the Zululand coast, spreading inland along the Thukela River. Generally, the conditions in the Drakensberg area may be described as “controllable and even eradicable” while the Midlands and Coastal Zone may be described as major problem areas. Alien vegetation threatens water security not only for large-scale agricultural production but also for local communities and landowners. The riparian areas will therefore need to be more closely monitored for alien vegetation since it impacts negatively on water production in high–yielding (high rainfall) catchments and consumes available water in low-yielding catchments (WRC, 1998).



Figure 13 : Natural Environment of the Thukela WMA

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Nottingham Road

Mooi River

Estcourt

Giants Castle

Champagne Castle

Fort Mistake

ElandslaagteBesters

LadysmithGeluksburg

Oliviershoek

Royal Natal N P Bergville

Cathedral Peak

WintertonColenso

Frere

Dannhauser

Dundee

Wasbank

Pomeroy

Tugela Ferry

Weenen

MudenKranskop

Jamesons Drift

Utrecht

GroenvleiCharlestown

Newcastle

Bu ffal o

Blood

Tu gela

Mooi River

Buffels River

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Thukela

Water Management Areas in South Africa

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Thukela Water Management Area :Natural Environment

TownscRivers

DamsUrban Areas

Problem AreasNatural Heritage SitesProtected Areas

Wetlands

Acocks Veld TypesCoastal Forest and ThornveldHighland Sourveld and Dohne SourveldHighland Sourveld to Cymbopogon-Themeda Veld Transition (Eastern Free State Highveld)Natal Sour SandveldNgongoni VeldNgongoni Veld of Natal Mist-BeltNorth-Eastern Sandy HighveldNorthern Tall Grassveld (Transition between Piet Retief Sourveld and Southern Tall Grassveld)Piet Retief SourveldSouthern Tall GrassveldThemeda Veld (Turf Highveld)Themeda Veld to Highland Sourveld TransitionThemeda-Festuca Alpine VeldValley BushveldMajor Catchments

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