Thukela River

Contents

I. Overview
II. Geophysical
III. Hydrology and Geohydrology
IV. Ecology
V. Climate
VI. Land-uses
VII. Populated places
VIII. Tributaries
IX. Dams
X. References



Overview

The Thukela is the largest river system in KwaZulu-Natal. The funnel shaped
catchment area of the Thukela River lies predominantly in the KwaZulu-Natal. The
river and its tributaries, meandering through central KwaZulu-Natal, draining from the
Drakensberg escarpment towards the Indian Ocean.

The Thukela River rises in the Drakensberg Mountains near Bergville where peaks

rise to over 3 000 m amsl.

It then flows eastward from a steep escarpment across low mountains of high relief,
open hills of high relief and lowlands of low relief and thereafter through a deeply
incised valley until it reaches the Indian Ocean approximately 85 km north of the city

of Durban , Africa ’s largest port.
Zulu meaning:

"a riverthat acts with frightening suddeness"
a name derived from the verb "tuku"which means to astonish orto be
startled"
"the fearsome one"

The River extends latitudinally from 27.41 o to 29.40o S and longitudinally from 28.96o

to 31.44o E. Catchment area: 29 0362 km

Through South Africa ’s National Water Act of 1998 (NWA), the Thukela catchment
is now a designated Water Management Area; one of 19 in South Africa . By

implication, the NWA, in its manifestations ranging from a more equitable allocation
of water to the various demand sectors (including the aquatic environment) to

controlling / levying streamflow reducing activities, will in time have to be
implemented through a stakeholder-manager-driven Catchment Management
Agency for the Thukela (the “P” in HELP).

During the drought of 1995, when the level of the Vaal Dam was below 15%, the
transfer of water from the Tugela River to the Sterkfontein Dam and releases from
this dam to the Vaal Dam were the life blood of the Gauteng area. Without this

supply, homes and industries would have run dry.

The upper reaches of the Thukela River, upstream of the confluence with the
Bushmans River, includes the towns of Bergville, Ladysmith, Colenso and Weenen.

The Klip River is the main tributary in this area. This area is the source of water for

the Thukela-Vaal Transfer Scheme, which, inter alia, transfers water to the Vaal

River System. The transfer capacity of this scheme represents a large portion (about
30%) of the water resources available in the Upper Vaal Water Management Area,

which is the economic heart of South Africa.

The catchment of the Little Thukela River, a tributary of the Thukela River, is

characterised by large irrigation requirements (36 million m 3/a). Other water uses are
insignificant. The only significant dam in this area is the small Bell Park Dam. The
upper areas the Little Thukela are located in a nature reserve and areas adjacent to

the nature reserve have developed rapidly into popular tourist resorts. The
Bushmans River rises in the Drakensberg Mountain range and flows in a north -

easterly direction past the town of Estcourt to join the Thukela River near the town of
Weenen. The Sundays River flows in a south-easterly direction from the eastern

escarpment to its confluence with the Thukela River near the Bushmans River

confluence.

The Buffalo River is the main northern tributary of the Thukela River and flows in a

southeasterly direction from the eastern escarpment (Newcastle area) to its
confluence with the Thukela River near Nkandla.

The Mooi River rises in the Drakensberg Mountains and flows parallel to the
Bushmans River in a north-easterly direction to join the Thukela River near Muden.
The only town of any significance in the catchment is Mooi River. The predominant

land use in the catchment is commercial agriculture and there is large-scale irrigation
of pastures and summer cash crops. The transfer scheme situated at Mearns can

transfer water to the Mgeni River System.

Geophysical

Topography

The Thukela River and some of its main tributaries rise in the west of the catchment in the high
lying Drakensberg Mountain Range. The headwaters of the main stem Thukela River originates at
an elevation of some 3 000 m.a.s.l. The river then winds its way through gently rolling hills before
entering steep sided gorges below Colenso. This rugged topography continues down to the river
mouth only broken occasionally by flatter, more densely populated floodplains. The Little Thukela,
Bushmans, Sundays and Mooi Rivers meander down through the mountains through relatively
undulating terrain before joining the Thukela River. The source of the Buffalo River is also
reasonably high lying but flows through more rugged topography and gorges in the lower half of its

trajectory.

Geology

The upper and middle Thukela River flows eastwards through a succession
of sedimentary strata of the Karoo Supergroup, ranging from the younger
rocks of the Triassic System (situated just below the Drakensburg volcanics)
to the base of the Karoo succession in the Tugela Ferry area.

The geology of the catchment is very varied, including Basaltic lava of the
Drakensberg, Stormberg and Beaufort beds, old granites and gneisses,

beds of Table Mountain Sandstone
and rocks of Dwyka and Ecca
series. Thick grey to brown silty
sand is typical of the debris presently being discharged
by the Thukela into its estuary.

90% of the Thukela catchment is underlain, from the
high altitude west to the lower altitude east, by Triassic
basalt over Permian / Carboniferous sandstones and
shales with coal rich seams. Towards the east, older Devonian sandstones overlay Archaean

basement complex granites and gneisses, with the sequence largely mirror-imaged near the coast

as a result of monoclinal uplifting.

Soils

The geomorphology of the Thukela River is strongly associated with the
underlying geology and the erosion resistance of the various formations on a

regional scale is reflected by these characteristics. Parts of the catchment are
quite densely populated. The arid and often erosive landscape, coupled with
overgrazing and extreme pressure on natural resources has led to the loss of

vegetative cover, erosion, and sedimentation.

The average annual sediment load at the Thukela Mouth has been estimated

at 5.5 million tons

Major Land Cover

degraded grassland; degraded thicket and bushveld
unimproved natural grassland

Major "Natural" Land Cover (Note: veld=range)

Southern tall grassland (35%)
Natal sour sandveld (15%)
Valley bushveld (20%)
Highland sourveld and Döhne sourveld (18%)
Others (12%)

Hydrology

Due to the mountainous nature of the Thukela Water Management Area and its proximity to the
Indian Ocean, the rainfall is high by South African standards, ranging from over 1 500 mm per
annum in the mountains to about 650 mm per annum in the central parts of the catchment. As a

result of the high rainfall, there is substantial runoff
from the Thukela catchment, with the
Mean Annual Runoff ,estimated at 3 799
million m3 /a. Rainfall is however erratic and
years of prolonged drought in the central
and lower catchment alternate with very wet
periods.

The Thukela is said to have "terrible peak flood"

characteristics , so that during the rainy season

"it's not uncommon to see walls of muddy water

0,9m to 1,5m high advancing downstream, bearing trees, animals and detritus... As the speed of

the current increases 2 to 5 fold, wholesale movement of the river bed results, and the river often

changes course within its bed.

Streamflow:
MAR (Mean Annual Runoff): 4000 x 10 m6 3 (equivalent to 17% of the mean
catchment MAP)
Varies: 50 – 250 mm.annum-1 between subcatchments
Coefficient of variation of annual flow: 40 – 50% in Drakensberg mountains to >
150% in central valleys, mostly 60 – 100%, i.e. 4 – 6 x CV of MAP

January and February flows account for > 40% MAR, June to September together

for < 8% of MAR
Irrigation water requirement:

800 – 1200 mm.annum-1
30 – 100 mm in January
80 – 120 mm in July

Approximately 2% of agricultural land is irrigated

Solar radiation:
25 – 30 MJ.2m .d-a1yin January (midsummer)
13 – 17 MJ.2m .d-a1y in July (midwinter

Potential evaporation:
1600 – 2000 mm per annum
180 – 220 mm in January
100 – 110 mm in July

Geo-hydrology

The Department of Water Affairs data indicates that present groundwater usage in the Thukela
Water Management Area is about 2.75 million m³/a. This converts to a usage of only 100 m³/km²/a
over the Water Management Area as a whole, which is only some 0.4 per cent of the mean annual
recharge over the area. Usage is lowest in the areas of low-density population and highest in its
more densely populated rural areas. It is evident that present groundwater usage in the Water
Management Area is in the low to very low range in terms of the sustainability of the available
resource. Groundwater usage in the Water Management Area can thus be safely increased
considerably without detrimental impact on the resource. Increased groundwater use should
therefore not impact significantly on the surface water resource.

Groundwater harvest potential mostly in the range of 10 000 – 25 000 m 3.km 2.annum -1, restricted

primarily by the volume of effective storage. Average borehole yield over most of the Thukela
catchment is 0.6 – 0.8 litres.s -1 with some areas 0.8 – 1.5 litres.s-1. Groundwater quality, in terms
of total dissolved solids (TDS) is < 200 mg.litre -1in the west and 300 – 400 mg.litre -1 in the north.

Ecology

Overview

The aquatic riverine environment has been significantly modified in certain areas by development

pressure on the river system.

High sediment loads are produced, particularly from areas degraded by overgrazing.

Acid mine drainage and related treatment result in high levels of TDS

Land use activities impact on sustainability of freshwater and estuarine habitats and resources.

The Ecological Reserve has recently been determined for the Thukela River Catchment. Issues

with regard to the conservation of the aquatic riparian habitats of
this river are:

Soils in the Drakensberg Mountain Range is relatively
shallow. Pressure from human activities outside of the
protected areas, particularly in the subsistence agriculture
areas, is resulting in soil erosion with the consequent loss of
habitat and siltation of dams in the upper catchment. The
lower Drakensberg areas and specifically the Mweni Valley
are the most effected
Severe overgrazing and soil erosion problems are being
experienced in the Driefontein Block and Matiwaneskop
areas to the north west and north of Ladysmith. Similar
problems are being experienced on the land reform projects
around Weenen and Estcourt
The wetlands and sponges in the upper and middle

Drakensberg are at present not under major threat of destruction due to their remoteness
and the fact that this is a protected area. These resources need to be preserved as far as

possible due to their critical role in supplying baseflows in all the rivers

Concerns exist relating to basic human health resulting from inadequate sanitation, particularly in

rural areas.

Problems include:

high E.coli concentrations in sections of rivers
water borne diseases e.g. current incidence of cholera, frequent incidence of diarrhea

Health impacts of large (especially, proposed) dams in high temperature regions include

bilharzia risk.

Ecological damage:

Degraded grassland as a result of livestock pressure.

Loss of terrestrial biodiversity in lower catchment, also as a result of anthropogenic change

and pressure.

Loss of aquatic biodiversity as a result of inter-basin transfer and large impoundments for

irrigation.
Loss of wetlands

Aquatic Animals

The aquatic riverine environment has been significantly modified in certain areas by development
pressure on the river system. A number of indigenous fish species still remain along with exotic
fish species (including trout and bass) dominating the various dams along these watercourses.

Viable local fishing (crustaceans) industry is highly dependent on the preservation of the littoral
sand bar formed by sediment deposition offshore from Thukela estuary mouth. A major concern is
that proposed catchment development to further impound the Thukela and Bushmans Rivers will
result in sediment depositon within the proposed dams and reduced sediment transport
downstream.

Terrestrial Animals

The upper Drakensberg area along the border with Lesotho is a conservation area and much of
the fauna is protected. The environment in the upper parts of the catchment still has naturally

occurring small game and their predators, reptiles and a wealth of bird species.

Vegetation

The natural vegetation types of the Thukela
River Catchment follow a similar pattern to
its geology. Montane grasslands covers the
higher lying areas giving way to Southern
Tall Grassveld interspersed with invading
Acacia sieberiana savanna and tilled
agriculture in the lower parts of the Upper
Thukela Sub-catchment between Bergville
and Colenso. Moving downstream past
Colenso, vegetation slowly changes to
Valley Bushveld. Coastal grasslands and
sugar cane farming characterise the lower

part of the catchment. The Mooi River system is mainly modified by pastural farming practices with
areas of indigenous subtropical forests along the steeper parts of this sub -catchment. Cattle
farming bushveld dominates the Buffalo River Sub-catchment with the exception of montane
grasslands in the upper part of this sub-catchment. Aquatic weeds have not been noted as a

problem in the Thukela River Catchment.

Major "Natural land cover"

Southern tall grassveld (35%)
Natal sour sandveld (15%)
Valley bushveld (20%)
Highland sourveld and Dohne sourveld (18%)
Others (12%)

Of prime botanical importance around the Thukela estuary is the 200 ha expanse of the Hlogwane
Forest which is a remnant of indigenious coastal dune forest in a very fine state of preservation. It
is also known as the Seula Bush and extends southwards in a narrow strip to the northern bank of

the Zinkwasi lagoon.

Besides this, due to the encroachment of sugar cane onto the estuary surrounds (and eucalytptus
plantations on the northern bank), the flora of the Tugela estuary has little resource or ecological
value. This confirmed by Orme after having reported on the results of a survey of the Tugela

floodplain using colour infra-red imagery techniques.

Climate

Temperature

The Thukela River catchment experiences a wide
variety of weather conditions ranging from generally
wet and cold in the Drakensberg Mountains, to dry
and hot in the Thukela Valley from Colenso down
towards the coast, and hot and humid and reasonably
well watered at the coast.

Mid-summer (January) monthly means of daily
maximum temperatures generally range from about
26°C to 28°C, with the highest values of up to 32°C
occurring in the valleys while in the high Drakensberg
mountains they seldom exceed 20°C (Schulze, 1997).
The Drakensberg mountains also record the lowest monthly means of daily minimum
temperatures, with sub-zero means of minima not uncommon in July. Unlike the chilly

Drakensberg range of mountains, the coastal areas are fairly cool during mid-winter with means of

daily minimum temperatures averaging about 10°C in July.

Rainfall

The region receives most of its rainfall in summer between September and April. Snow falls are

common in winter along the Drakensberg
Mountain peaks, which melt fairly quickly. The
average rainfall ranges from about 1 500 mm
per annum in the mountains to about 650 mm
per annum in the central parts of the
catchment. There is a slight increase in rainfall
towards the coast.

As is the case with all climate related
variables, rainfall in the Thukela catchment,
and with that its major ecological regions as
defined by Edwards (1967), displays
considerable spatial variation. Mean annual

precipitation (MAP) in the Thukela ranges from around 2 000 mm in the Drakensberg to as low as
550 mm in the drier, lower-lying valley regions. Significant from a water resources management
perspective is the relatively high inter-annual variability of rainfall, with CVs generally in the range

of 20 – 30%.

The driest year in 10 records only about 60% of MAP. Equally as important as its variability is the
strong concentration of rainfall in the summer months. Most of the rainfall (> 80%) is received
during the wet summer season between October and March (Schulze, 1997). The coastal region
is an exception because it has relatively wet winters during which about 30% of the annual rainfall

is received. In relation to the other months, January is the wettest month with the rainfall ranging
between 100 – 300 mm (mostly 120 – 150 mm). June and July are the driest months, with means

of those respective months’ rainfalls over most of the catchment being about 10 mm .

Land-Use

Agricultural

From a water resources point of view, irrigation is a significant land
use. According to the Thukela Water Management Area Report,

the estimated irrigated area is some 2762 km .

Commercial dryland agriculture dominates the Sundays River

catchment and there are also fairly large tracts of tribal / communal
land in the lower reaches of the catchment . Irrigation is supplied

from farm dams or from run-of-river flows.

The predominant land use in the Mooi River catchment is
commercial agriculture and there is large-scale irrigation of
pastures and summer cash crops. Craigieburn Dam on the
Mnyamvubu River supplements water supplies to approximately
2000 ha of predominantly citrus farming irrigation downstream of
the dam and along the Mooi River at Muden.

Another important land-use that has an impact on the water resources of the Thukela River

catchment is commercial timber.

The estuary is surrounded by flat alluvial land or rolling hills, all used for the cultivation of sugar

cane.

Subsistence dryland agriculture (mainly maize)

Nature Consevation, Reserves and Tourism

The Thukela Waterfall at a total height of 850 m is one of the

highest waterfalls in the world and can be viewed from the
Drakensberg KwaZulu-Natal.

A popular walk is the 23km hike along the Thukela (Tugela) River
to the tunnel. Although along the trail is not particularly strenuous
and most people should be able to manage it. The trail follows the
river right up into the Amphitheatre. Towards the end of the hike
there is a natural tunnel that has been carved out of the rock by
the river. Above the tunnel it is possible to continue following the
river until the spectacular Thukela Falls comes into view. The

word Thukela comes from Zulu and means "Startling One"

Another trail to the foot of the Tugela Falls starts at Royal Natal
National Park . The easy seven kilometre gradient up the Tugela
gorge winds through indigenous forests. The last part of the hike

to the Tugela Falls is a boulder hop. A little chain ladder takes you over the final stretch from
where you have a stunning view of the falls rushing down the Amphitheater in a series of five

spectacular cascades.

Industries and Mining

Industry as a land-use is not significant in the Thukela catchment. Small to medium-sized
industries are situated in the peripheral industrial zones in and around Newcastle, Ladysmith and
Estcourt. The biggest pulp and paper mill in Africa, SAPPI, is situated immediately bove the
estuary. The Isithebe industrial area is located close to the river mouth.

Coal mines scattered all over the northern parts of the Thukela River catchment have either been
closed for a number of years or are in the process of closing down. Many of the older mines were
never rehabilitated adequately. Consequently, these mines produce acid mine decant that enters
the Thukela River system. The worst affected areas are around Newcastle (Buffalo and Ngagane

rivers).

Populated Places

Name Province District Municipality Population River or
Bergville Uthukela Ukhalhlamba tributary

Colenso Uthukela Emnambithi-
Dannhauser Amajuba
Dundee Ladysmith
Estcourt Dannhauser
Glencoe
Ladysmith Umzinyath Endumeni 24,754
Madadeni 25,767
Mandini Uthukela Umtshezi Bushman's
Mooi River River
Newcastle Uthukela Emnambithi 89,087
Nkandla Klip River
Utrecht Amajuba Utrecht
Weenen Thukela
Umzinyathi Endondakusuka River
Mooi River
Uthukela Mooi Mpofana
Buffalo
Amajuba New Castle 219,682 River

Umzinyathi Nkandla

Amajuba Utrecht

Uthukela Emnambithi-
Ladysmith

Population

Generally sparsely populated with 5
–20 inhabitants per km2 in the west,
and > 20 inhabitants per k2min the
east; large areas of rural
communities dependent on
subsistence agriculture.

Greater concentrations associated with localised coal mining.

Overall less than 300 economically active workers per 1000 population

Tributaries

Tributary Notes
(the largest tributary, from the north)
Buffalo River
Bloukrans River (from the soutwest)
Bushmans River (from the north)
Klip River (from the southwest)
Little Thukela River (from the southwest)
Mooi River (from the north)
Sundays River

Dams

CRAIGIE BURN DAM
Max. Capacity: 23.4 mil.cub.m
Constructed on the Mnyamvubu River in 1963 .
The dam supplements water supplies to
approximately 2000 ha of predominantly citrus
farming irrigation downstream of the dam and
along the Mooi River at Muden.

DRIEL BARRAGE DAM
Max. Capacity: 8.7 mil.cub.m

Water is released from Woodstock Dam to Driel
Barrage, from where it is pumped to a transfer
canal that feeds the Jagersrust Balancing Dam.

NTSHINGWAYO DAM (previously known as

Chelmsford Dam)

Max. Capacity: 195 mil.cub.m
Ntshingwayo Dam (previously known as
Chelmsford Dam) which was completed in 1961
and raised in 1982. . The dam was built to supply
water to the town of Newcastle, Eskom’s thermal
power station and irrigation farmers downstream.
Releases are sometimes made to dilute factory
spillages that end up in the river system

WOODSTOCK DAM

Max. Capacity: 380.8 mil.cub.m

Located on the upper reaches of the Thukela
River, is the main source of water for the
Thukela-Vaal Transfer Scheme.

SPIOENKOP DAM

Max. Capacity: 271.3 mil.cub.m

Constructed to regulate flow downstream of the
Driel Barrage to mitigate the effect of the transfer
scheme. The dam also supplies water to
Ladysmith and supports water requirements for
the farmers between the dam and the confluence
of the Little Thukela River. Releases are also
occasionally called for to dilute the effluent
discharged by Sappi into the lower Thukela near
the river mouth. The Tugela-Mhlathuze Water
Transfer Scheme at Middeldrift can also be
supported from Spioenkop Dam if necessary.

WAGENDRIFT DAM

Max. Capacity: 58.5 mil.cub.m

The Wagendrift Dam was constructed in 1963 on
the Bushmans River to supply approximately
3000 ha of irrigation between the dam and the
Thukela River. Up to 2 m3 /s is released from the
dam for environmental and irrigation
requirements if the dam is not spilling. Estcourt
obtains water for domestic and local industrial
purposes directly from the Wagendrift Dam and
discharges treated effluent back into the river
downstream of the dam.

ZAAIHOEK DAM
Max. Capacity: 193 mil.cub.m
Built in 1988 with an original capacity of 193
million m3. Zaaihoek Dam is on the Slang River
(tributary of the Buffalo River). Used to transfer
water to the Vaal system and the Majuba Power
Station. Can also supplies demands downstream
of the dam by releasing water into the Slang
River.

Bell Park Dam

Max. Capacity: 7.5 mil.cub.m
The dam,is situated in the upper reaches of
Little Tukela River. The dam is used mostly
for recreational purposes and its potential is
not fully utilised.

Kilburn Dam

Max. Capacity: 35.7 mil.cub.m

Slangdraai Dam

Max. Capacity: 10.3 mil.cub.m
On the Sundays River.

References

1. Department of Water Affairs and Forestry, South Africa. 2004. Internal
Strategic Perspective: Thukela Water Management Area : Prepared by Tlou &
Matji (Pty) Ltd, WRP (Pty) Ltd, and DMM cc on behalf of the Directorate:
National Water Resource Planning (East). DWAF Report No. P WMA
07/000/00/0304.

2. The Estuaries of Natal by George Begg

3. Submitted by School of Bioresources Engineering and Environmental

HydrologyUniversity of Natal Pietermaritzburg, 3201 South Africa

4. Schulze, R.E., Dlamini, D.J.M. and Horan, M.J.C. 2005. The Thukela
Catchment : Physical and Socio-Economic Background . In: Schulze, R.E.
(Ed) Climate Change and Water Resources in Southern Africa: Studies on
Scenarios, Impacts, Vulnerabilities and Adaptation. Water Research
Commission, Pretoria, RSA, WRC Report 1430/1/05. Chapter 10, 191 - 209.

5. Midgley, DC, Pitman, WV and Middleton, BJ (1994). Surface Water
Resources of South Africa 1990. Volume VI. Drainage Regions U,V,W,X -
Eastern Escarpment– Appendices and Book of Maps. WRC Report Number
298/6.1/94.

6. Professor R.E. Schulze University of Natal , Pietermaritzburg, South Africa
School of Bioresources Engineering and Environmental Hydrology (BEEH)

7. www.unescohelp2007.com/Thukele.doc

8. Tugela Waterfall photo: [email protected]



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