CHAPTER 9: CONCLUSION
As mentioned earlier in the statement of the problem the Hennops River has gradually
deteriorated in terms of its water quality and hydrological conditions over the past three decades.
This can mainly be attributed to the catchment’s position which is situated between
Johannesburg and Pretoria within the provincial boundaries of Gauteng – the smallest of South
Africa’s nine provinces but housing approximately 8,8 million people and regarded as the
economic powerhouse of the country. The study area’s associated land use, activities and
increasing urbanisation taking place negatively affect the Hennops River and its principal
tributaries. Moreover, the river system is the responsibility of a number of local authorities,
making co-ordinated planning and management difficult.
Owing to the deterioration of the water quality and hydrological conditions of the Hennops River
affected parties concerned such as local authorities, residents and business people of Centurion
have started considering the Hennops River as a liability instead of the environmental asset with
intrinsic values it offers to its surrounding environments. Causes of its deteriorated water quality
and hydrological problems needed to be ascertained so that rehabilitative and mitigatory
measures could be proposed and it is for this reason that this study was conducted.
As such, this study’s main aim was to establish the present water quality condition and
hydrological status and condition of the Hennops River. The water’s suitability for aquatic
ecosystems well-being was also determined as fish mortalities continue to occur in sections of
the Hennops and its principal tributaries. These sections include the upper Hennops River and
Centurion Lake forming the centre of Centurion’s CBD. Once the overarching problems and
causes of these were determined and understood, rehabilitative and mitigatory measures were
proposed towards the improvement of the water quality and hydrological status.
Before this could be achieved the meaning of water quality, its various physical and chemical
constituents affecting aquatic ecosystems and the recommended Target Water Quality Range
(TWQR) as stipulated by DWAF for the well-being of these were reviewed and discussed.
Added to this, hydrology and its relevance in terms of this study were explained.
111
Conclusion
The study area also needed to be described. Not only was attention given to the position of the
Hennops River and its principal tributaries, but also to the associated physical features and
existing land uses within its boundaries. In order to gain insight, understanding and ascertaining
the causes of water quality and hydrological problems, it was deemed necessary to describe the
study area in detail.
Following this, existing knowledge of previous conditions of the study area was reviewed so that
a comparison could be made between previous and existing conditions. It was found that the
Hennops River catchment had already experienced deterioration between the 70’s and 90’s due
to factors such as increasing urbanisation, industrialisation and rapid human settlement. Coupled
with the fact that the study area is currently experiencing further developments and an increase
in human population, the rationale of this is that an improvement in water quality and
hydrological conditions of the rivers without implementing rehabilitative measures will not be
possible. Therefore, rehabilitative measures need to be implemented.
The existing knowledge of the study area was then compared to the most recent water quality of
the study area i.e. the two year period between January 2002 and December 2003. Data in terms
of water quality monitoring results were collected from two authorities responsible for
monitoring the Hennops River, viz.: DWAF and CTMM. Only certain water quality constituents
were collected and analysed i.e. those having an effect on aquatic ecosystems (Table 14). Since
water quality monitoring results would differ along different sections of the Hennops and its
principal tributaries, the actual positions of the DWAF and CTMM monitoring points were
described with the areas of the study area represented by their monitoring results.
The recent water quality data showed that only certain water quality constituents could be
causing debilitating effects on aquatic ecosystems i.e. five out of the ten different water quality
constituents showed mean concentrations not complying to the TWQR. These constituents were
dissolved oxygen, ammonia, chloride, nitrate and nitrite nitrogen and orthophosphates. As
expected, the upstream sections of the study area comprising the formal and informal settlements
of inter alia Tembisa, Ivory Park and industrial areas of Clayville and Olifantsfontein, had
higher mean constituent values than the downstream sections. This can be attributed to the land
use and activities present in these areas surrounding the Kaalspruit (Table 15).
112
Conclusion
In terms of comparing the recent water quality data to the data from the past studies, it was
concluded that the Hennops River catchment has experienced deterioration in terms of its water
quality over the past three decades. The comparison showed that mean constituent
concentrations of ammonia, phosphorus, COD and chlorine have increased over the years.
The Hennops River and its principal tributaries, especially the Kaalspruit and Olifantspruit,
experience not only water quality problems but additional hydrological problems as well. These
problems were dealt with in detail and include typically the erosion of the Olifantsfontein
wetland and riverbeds and riverbanks of the Kaalspruit and Hennops River due to the sediments
released from the wetland. Furthermore, large amounts of debris are also carried downstream by
floodwater flows. This debris consists of urban litter and vegetation debris.
Rehabilitative and mitigatory measures have been proposed. They are aimed at improving the
water quality and hydrological problems of the Hennops, Olifantspruit and Kaalspruit Rivers.
Measures proposed include the construction of sediment traps and debris traps, the erosion
control of riverbeds and riverbanks, rehabilitation of the Olifantsfontein wetland and the
construction of another in Centurion.
It is recommended that monitoring of the water quality of the Hennops and principal tributaries
continue to be conducted by DWAF and CTMM in order to monitor the state of these rivers on a
continual basis. Significant changes in water quality should be investigated to determine causes
for this and to address such problems. Furthermore, the situation of the Hennops River system
must be one of the more important environmental issues between Johannesburg and Pretoria.
Therefore, the situation illustrates the need for rivers (and water management areas) to be
managed holistically as opposed to the fragmentalised planning by different local councils and
government departments which is currently the scenario. Responsible parties need to formulate
and follow an environmental management plan which will address the upstream water quality
and associated problems as these in turn are causing problems such as the silting-up of Centurion
Lake and the loss of aquatic biota further downstream.
113
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