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eWISA
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THUKELA:
MAIN INDEX |
ALPHABETICAL
LIST OF RIVERS |
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Map
of the THUKELA River |
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TEMPERATURE
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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.
Ref.1.
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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. (Ref
4)
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RAINFALL
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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.
Ref.1.
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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%
(Schulze, 1997). (Ref 4)
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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. (Ref 4)
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References |
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Ref 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.
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