Restoration of the dams at Technopark:
Preliminary Action plan
JJ Kellermann, 15381528
Private bag X1, Matieland, University of Stellenbosch, Department of Conservation Biology and
Entomology.
Table of Content
Executive Summary........................................................................................................................ 3
1. Introduction................................................................. ............................................................... 4
1.1. Current situation and layout……………………………………………………….....……
5
1.2. Construction material................................................................................................... 7
1.3. Surrounding Biota........................................................................................................ 8
1.4. Role of Plant Biota....................................................................................................... 12
1.5. Role of Animal Biota..................................................................................................... 13
2. Water Quality............................................................................................................................... 14
3. Problem Summary ...................................................................................................................... 16
4. Usual Problems........................................................................................................................... 16
5. Recommendations....................................................................................................................... 17
5.1. Physical and mechanical removal................................................................................. 18
5.2. Dredging and flushing................................................................................................... 18
5.3. Bottom layer replacement............................................................................................. 19
5.4. Shading......................................................................................................................... 19
5.5. Aeration......................................................................................................................... 20
5.6. Nutrient removal........................................................................................................... 20
5.7. Herbicide and chemical removal.................................................................................. 21
5.8. Biological treatment...................................................................................................... 21
5.9. Organic Water Solutions............................................................................................... 22
5.10. Fire.............................................................................................................................. 22
6. Conclusion ................................................................................................................................. 23
7. References................................................................................................................................... 26
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Figure 1 Map of Technopark dams
Figure 2 Schematic representations of Technopark dams
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Executive Summary
The vision of Technopark suggests the greening of the business park in collaboration with the University of
Stellenbosch and the government by creating knowledge networks and innovation for sustainability. To initiate
this vision, this project was put underway to rehabilitate and transform the dams included in Technopark
towards a sustainable trajectory. An assessment of the fauna and flora, together with current status report by Du
Preez (2011) of the 9 dams, indicated that attention is needed to re-establish the water system.
These dams are primarily recreational dams with an ecological importance that adds scenic beauty to the
business area, but since water became stagnant, vegetation has increased, water levels dropped, siltation
occurred and overall water quality decreased.
In order to achieve an ecologically based method of rehabilitation of the Technopark dam water cycle, in a
financial viable process, all aspects and possibilities need to be considered and explained. After many
conversations with different ecologists, this report is only a preliminary draft and further investigation is
advised.
Two options however can be considered in the meantime, depending on the period of results. The long term and
most recommended process would be to reinstate the flow of the water, by repairing the water cycle. The
moving water will aerate the system, making fish and plants more active, which will remove stagnant and
abundant nutrients. With the nutrients decreasing, aquatic plant competition will increase which will lead to an
ecologically controlled plant population. This may perhaps additionally decrease the silt. This method does
however require time and assessment of results.
A short term result would be to start removing some of the lilies and reeds, but the methods can vary
excessively. Emergent plants and reeds should be controlled with specific herbicides and removed accordingly.
Cutting and fires will only lead to current control and further sprouting of the plants. Silt can be removed by
raking it closer and removing it by hand. All the processes used should avoid damaging the bentonite bottom
layer of the dams, as it may cause an increase in turbidity or leakage.
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1. Introduction
A vast number of studies and advice exist on the establishment of new dams. The rehabilitation of already
existing dams with their unique features and problems is a more challenging job. Studies claim that premature
wear and deterioration of dams can be caused by insufficient investigation of the construction region, design
deficiencies, practical implementation and a lack of dam adjustment to the actual conditions in which the
construction occur (Stol’nikov, 1969). In the case of Technopark, improper implementation and lack of
maintenance led to a broken water system that now lie stagnated, while accumulating plant matter.
There are many factors influencing the Technopark dam system, some are negative, whilst others are positive.
These factors as well as factors that affect the growth and restraint of the plants will be discussed as well as
manners in which the dams should be cleaned, if necessary.
Constructed in 1990, the dams were designed to add aesthetical value to the environment as a water feature. A
chain of dams were assembled that support water, flowing over from one dam to the next with gravity. The
water is introduced into the dams from the Theewaterskloof irrigation system or treated municipal water. The
untreated water would have flowed from dam 4, where it was introduced, to dams 3, 2 and 1, where after
flowing over into an overflow pump, was pumped to the s-channel and made its way down to dams 5,6,7 and 8.
From dam 8 the water flowed through ground channels to dam 9, which is a more natural, balancing dam. The
water would be used from dam 9 to irrigate the entire Technopark area.
An irrigation sprinkler system was initially installed for all public open spaces of Technopark. The irrigation
was planned occur from 20:00 to 06:00 the next day. A certain lag time to balance the water in dam 9 for the
irrigation system, was made to ensure that dam 9 never overflowed. The designed flow was 35 l/s. A certain
volume of retention water exist above the full supply level of each dam which gravitated down the system until
all dams reached their fully supply level until it this volume of water flowed into dam 9. The irrigation supply is
linked to the demand of the irrigation system, and therefore the timing of the activation input to dam 4 is linked
to the actual volume of water pumped by the irrigation pump system.
In order to prevent algae growth, the dams were designed to be roughly 1.5m deep and required a certain
minimum flow velocity. The flow pattern was designed to produce a closed system of “plug flow”. Ideal plug
flow is when water introduced at the top of a system moves down the channels as a unit to attempt water
introduced at the same time to reach the end of the system roughly at the same time. The stepped channels on
the southern boundaries of dams 5, 6 and 7 and the water overflows from the upstream dam along these
channels created a side input opposite to the main concrete overflow input. To avoid having a dead supply
position on the boundaries of the dams, further inputs were designed as a water cascade/small waterfall. A third
piped overflow is taken from the upstream dam with flow introduced to the western edge of the dam below
surface level. This third overflow is invisible to an uninformed person. Each dam system varies slightly from
dam to dam. (Du Preez, 2011).
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If the Technopark dams entail removing aquatic vegetation and pollutants it will be necessary to use a complex
variety of physical, chemical and biological processes (Gersberg et al., 1986).
To develop a predictive understanding of how to treat these water systems properly, it is needed to emphasise
appropriate mass balance and study the role of the aquatic plants (Rogers et al., 1991).
The fact that the plants in the dams do not struggle with growth, indicate that the nutrient level in the dams are
high enough for successful growing, but an abundance of nutrients will lead to plant and algae problems in
dams. It is well known that plants use photosynthesis to produce oxygen and energy from the use of sunlight
and Carbon dioxide. During periods of no sunlight, such as at night, the system is reversed with carbon dioxide
being produced and oxygen being used. Oxygen levels in the dams drop during the night, giving off carbon
dioxide and posing a threat to the fish and the overall water quality. Bacteria start to decompose the organic
material, by using the oxygen of the dam, leading to a overall decrease in dissolved oxygen, as seen in dam 8
where plants are abundant and bacteria visible (Verdouw, 2008).
Plants are not the only factor causing problems in the dams. The surrounding environment with rich plant
diversity attracts animals, especially birds, who then, with their waste, add nutrients to system, causing an
unbalanced dam ecosystem (Verdouw, 2008).
The bottom of the dams is made from bentonite, to seal the surface from water drainage. The properties of
bentonite will be discussed in order to decide on the restoration method and its possible reactions on the
ecosystems of the dams.
The clarity of the water can pose high water quality problems. Clarity or turbidity can be caused by several
factors, but usually the effects are the same; decreased aesthetics and cloudy water.
It is easily concluded that in order to achieve well balanced dams, it will involve an in depth study of the whole
intricate system. This paper however, is only a preliminary report and is presented as a draft with possibilities
and current standings.
1.1.
Current situation and layout
The Technopark dams were not created for ecological or ecosystem purposes but for irrigation and in an
aesthetic manner. The water is supposed to flow through the chain of dams by means of gravity when
overflowing occurs or via a pump system. Since the water of the dams has been stationary for a few years and
the management of the plant population have not received sufficient attention, the plants included in the area,
especially in the dams, are uncontrolled. The dam system includes 9 main dams and an S-channel system.
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The current situation of each specific dam is discussed below. The numbering of the dams is done according to
Du Preez (2011). Treated or untreated water, flow into dam 4, where it drains in an overflow manner to the
dams to the West namely to dam 3 over to dam 2 and thereafter over to dam 1. From dam 1 it is pumped to the
S-channel where it flows down to dam 5 all through the system and its weirs until reaching dam 9. The water in
dam 9 is supposed to be pumped back into dam 4 in order to create a continuous flow of water.
Dam 4: The plants in this dam mainly include blue water lilies. The water of this dam is odourless, clear and
had a dissolved oxygen level of 7.43 mg/L. The abundance of plants in this dam can be concluded as under
control and healthy. It is advised to leave the plants of dam 4 as it is. Many bottom sediments are visible.
The vegetation in dam 3 near the overflow from dam 4 consists of Typha capensis which act as a filter for the
pollution (bags, bottles, papers etc.). This creates an easy manner of pollutant control, but the pollution should
be removed regularly to avoid unhealthy conditions, unwanted odours and muck.
Dam 3: The plants in this dam show great success in their growth but many of the Typha capensis in the
middle can be removed. The manner of removal will be discussed later with reference to the bentonite layer.
The water of dam 3 is clear and odourless.
Dam 2: This dam is also healthy as the water is clear and odourless with submerged plants indicating a well
balanced population. Ecologically, no treatment is necessary.
Dam1: This dam is in a bad condition with very low levels of water, extreme levels of vegetation cover and
land in the centre with an ant colony. The inlet is also overgrown and evidence of leakage exists (Typha
capensis).
S-channel: This part of the water system is in serious need for rehabilitation. An excessive reed (T. capensis)
population exist and restrict water flow with indications of leakage. The Typha capensis is included in this
channel and removal may be considered.
Dam 5: This dam has a healthy, well balanced plant population with no odour. Although the water has become
murky the dam can be kept as it is for the time being.
Dam 6: This dam is an indication of the result to use physical power as a possibility in order to remove the
aquatic plants. The dam has no plants left and has high turbidity, but no odour. No further removal of plants is
thus necessary. The turbidity can be ascribed to a disturbance to the bentonite layer.
Dam 7: The water of this dam was not tested but has previously indicated low pH levels (Du Preez, 2011). The
plants (Blue water lily) in dam 7 are healthy but a small percentage may be removed to keep it in balance. The
water is murky due to the overflow of bentonite contaminated water from dam 6.
Dam 8: The western part of the dam is in an appalling condition, with silt and island-like areas, which indicate a
definite disturbance. The dam has a disproportionate amount of plants and an oil layer is also visible. This dam
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requires extensive attention since fish are observed in the dam. The dam is only slightly turbid, but an odour
was noticeable. Dam 8 water was tested as well and compared to dam 6. The silt and a percentage of the plants
need to be removed.
The ground channels that lead from dam 8 to dam 9 is extremely over vegetated and require removal of nonaquatic plants. A neat divide should be made between the grass (kukuyu grass species) and preferred aquatic
vegetation. The last dam, dam 9, stretching from the channel linking dam 8 and 9 to the dam itself was designed
to be ecological. The water would have flowed from dam 8 without further concrete channels to dam 9 (Van
Eeden, 2011). Since the flow to dam 9 is unpredictable and the dam supports itself with vast vegetation, it does
not have any silt or fish such as dam 8.
Dam 9: Logically most of the suspended debris will flow down and accumulate in the lowest dam or in still
standing water. The last dam is also over populated with Typha capensis and it would be recommended to
remove some of these plants at the inlet. The water is however clear and odourless. Acacia mensii, an extreme
invasive species are noticeable around dam 9 and require immediate attention.
Dams 3, 1, 7, 8, 9, the S-channel and the ground channels should all undergo plant removal activities. The best
removal process will be discussed and decided upon with reference to its possible outcome.
1.2.
Construction Material
Since this report studies the ecology of the dam, the manner in which the bentonite ground cover was
completed can be seen in the status report of Du Preez (April 2011). All the dams at Technopark consist of this
bottom layer of clay as a sealant.
Bentonite is a form of clay with the special ability to form thixotrophic gels when in contact with water. The
high capacity and ability of this clay to exchange cations and absorbs large quantities of water makes bentonite
the perfect mineral to waterproof and seal surfaces of water bodies. Bentonite can also serve as an extender in
adhesives, paints, cosmetics and medicines but are primarily used as stabilizers and fillers. Furthermore
bentonite can act as a bonding agent in animal feed but more importantly as a purifier for wastewater. With this
said and the fact that bentonite has a low toxicity to aquatic species, it is well adapted for fish ponds and dams
(Adamis & Williams, 2005).
Bentonite can be rock or clay based industrial material, which usually consists of a mixture of minerals,
therefore it is not able to report a specific molecular formula for bentonite (Adamis & Williams, 2005). The
chemical composition of bentonite does however affect its usage. The properties of saturated bentonite are
characterized by the hydrated clay minerals (Fujii et al., 2003)
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Bentonite mineral is soap-like and greasy to the touch. The colour of dry bentonite is pale blue or green and
darkens to brown, yellow or red when exposed. This clay has the ability to increase in volume up to 12–15
times its dry bulk by absorbing large quantities of water along with a high cation exchange capacity. Bentonite
is widely distributed and dispersed by air and moving water. With the swelling of bentonite in soil interstices,
bentonite plugs the voids in the soil with its tiny average particle size, which then creates a barrier of very low
permeability (Adamis & Williams, 2005).
Adamis & Williams (2005) explains that the high cation exchange capacity allows bentonite to enhance the
retention of wastes, especially in heavy metals. If the sodium bentonite is mixed with soil it will form tough,
flexible mastic that is highly durable and will not easily rupture.
Preferably, bentonite with a dominant sodium ion is used for sealing and waterproofing, whereas low-swelling
calcium bentonite is preferred for filtering, clarifying, and absorbing and for serving as a filler, stabilizer,
extender, carrier, bonding agent, or catalyst (Adamis & Williams, 2005).
Bentonite can be added to water-filled dams when draining is unpractical. To do so, bentonite in its granular
form should be distributed from a boat over the leak or the entire dam surface. If powdered bentonite is mixed
with water, it forms a slurry matter that can be poured and sink to the dams’ bottom. The best results are
achieved when the clay mix well with the bottom soil, although this may be difficult to obtain when the dam is
filled with water. The technique of pouring bentonite in a water-filled dam is less effective to reduce pond
seepage and may not be financially practical if the entire dam needs to be sealed. The best data for bentonite
application rates will be provided with laboratory or field performance tests (Keese, 1988).
The dispersive nature of bentonite can also create problems such as piping, which will create leaching and
erosion. It would not be recommended to physically pull any surface attached aquatic plant from a bentonite
dam (Van Eeden, 2011).
1.3.
Surrounding Biota
Plant and surrounding fauna species play an enormous role in the structure of the dam ecosystems. Available
nutrients are one of the biggest influences fauna and flora may have on the water system as discussed later.
Essentially, only the most important fauna and flora species in the Technopark area is accounted for.
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Many other occasional visitors can be seen.
The silt that occurs in dam 8 may be a form of filamentous algae.
1
Blue waterlily (Nyphaea nouchalia or odorata)
Water lilies are perennial plants that may form dense colonies. Bright green floating leaves are roundly shaped
and 15 to 30 cm in diameter with a slit of 1/3 the length of the leaf. As the name imply, white water lilies form
white petals with yellow centres, while blue water lilies form blue flowers, both arise from separate stalks. The
flowers open in the morning and close in the evenings. These flowers stick out above or float on the water.
Importantly for removal, these water lilies can spread from the rhizomes or from the seeds. Lilies are highly
invasive plants that grow in clear water (Masser, 2010).
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Mechanical or physical control options for water lilies include cutting and digging out rhizomes. No biological
removals are known for water lilies, while chemical control includes fluridone, imaxamox, glyphosate,
triclopyr, and 2.4-D that work excellent. 2.4-D compounds are systemic herbicides that are absorbed and move
within the plant to the site of action. Systemic herbicides usually act slower than contact herbicides (Masser,
2010).
2
Sedge (Schoenoplectus paludicola)
There are more than 100 types of sedges, most of which are difficult to identify without using detailed botanical
keys. Generally sedges are perennial grass-like plants that grow in moist soils or shallow water. Growing in
thick clusters, sedges stems are usually triangular, with spikes on the upper part of the plant. Sedges can be
removed through mechanical and physical methods, much like water lilies. They can also reestablish from
remaining roots or seeds. The only known biological manner of sedge removal, involve goats foraging on these
emergent vegetation. Chemical control options include imazapyr and glyphosate (Masser, 2010).
3
Bulrush (Scirpus spp.)
Several species of bulrushes exist that are also perennial grass-like plants. Growing in shallow water or moist
soils, these plants can grow to dense colonies from rhizomes. Bulrush colors can be lightly gray-green to dark
green, with round soft stems or triangular stems that come to a central point. The flowers of a bulrush will occur
just below the top of the stem. Biological control for bulrushes includes mostly bird species as well as goats.
Ducks will consume the seeds of bulrushes while other birds, such as geese consume the rhizomes and early
shoots of the bulrush. Further physical or mechanical management options comprise of cutting and digging out
the plants and their rhizomes. Frequent mowing has shown to be effective for bulrush control. To chemically
remove bulrushes it is necessary to use products with glyphosate as active ingredient. Bulrushes are known to
be able to aggressively invade ponds (Masser, 2010).
4
Dallis grass (Paspalum dilatatum)
Dallis grass is a perennial tussock grass with short rhizomes, tillers and loose, flexible inflorescence. The
inflorescence has tufts of white hair at the junction of the clusters and the central axis. Paspalum dilatatum
grows in humid places such as wetlands and near rivers, flowering from November to February. Paspalum is
also often found as a weed in gardens, fields, along roadsides and lawns, as in this case. They thrive in clay and
loam soils and may even be a lovely meadow grass that can endure heavy trampling and grazing. Dallis grass is
often planted for grazing, silage and hay, especially in wet soil. Paspalum is susceptible to ergot (Claviceps
paspali) a dark colored poisonous fungus that grows on the spikelet. This can lead to poisoning of animals that
feed upon them. Paspalum should preferably be controlled in the seedling stage because it is difficult to combat
them at maturity. This introduced species is originally from South America (Brazil and Argentina) (Van
Oudtshoorn, 1999)
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5Vasey's
grass (Paspalum urvillei)
Paspalum urvillei is a dense perennial tussock grass with an upright stem and basal leaf sheath that is densely
covered with stiff hair. The leaf sheath has a rough leaf edge. These grasses also usually grow in moist soils and
flower from October to April. Paspalum urvillei grows in humid places such as wetlands and riparian areas or
road reserves and where water collects. Mostly found in areas with loam and clay soils. In several countries this
grass is planted as cultivated pastures and grows especially well in wetlands. As the plants get older the plant
palatability decrease and may quickly become a weed. Control measures should be applied early, as it is
difficult to control at maturity. Paspalum urvillei is found in many tropical areas but initially come from
Argentina and Uruguay (South America) (Van Oudtshoorn, 1999).
6
Cattail (Typha capensis)
These reeds has slightly flat to round leaves that can grow to 1.5 or 3m high. The dense dark brown, cigarshape at the end of the spike is the flowers, called the catkin. Cattails can grow partially submerged or in marsh
areas with nonpermanent still standing water. Since the seeds of T. capensis are blown by the wind, float on
water and grow from underground rhizomes they can spread rapidly. The lower leaf portions and rhizomes are
eaten by geese and rats. Mechanically, cattails can be removed by digging up the rhizomes and removing them
from the dam. To remove the whole plant requires much care since cutting off the tops of the plant will not kill
them and therefore rhizomes underground should also be eradicated. This option is best applied when cattails
initially invade an area. Once cattails are established it is difficult to control, although frequent mowing has
proven to be effective. Chemical controls by active ingredients such as diquat, glyphosate, imazamox and
imazapyr have proven to be successful in treating cattails. As noticeable in Technopark, these, Typha capensis
can be aggressive pond or wetland invaders (Masser, 2010).
7
Common reed (Phragmites australis)
The common reed is a perennial reed, with upright non-branching stems that generally form dense stands in wet
places, such as in rivers and wetlands. Phragmites bloom from December to June and are of little value for
grazing. These reeds play an important ecological role in protecting soils from flooding, providing shelter to
many species of birds and animal as well as filtering water. People utilize Phragmite plants for signs, thatch
mats, construction work and even for erosion prevention. This species is known to probably be the most
widespread plant in the world (Van Oudtshoorn, 1999). Common reeds propagate from seeds or rhizomes.
Many bird species utilize the thick common reed vegetation as shelter and the seeds as a food source (Masser,
2010). The dense tall stands of the common reed may choke out native plant species and diminish wetland
areas for other wildlife. Cutting the dormant stalks to a height of 60 to 90cm followed by the application of
target herbicides that are approved for herbicides has proven to be successful to suppress new growth of
common reeds (Williams & Zimmermann, 2010).
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1.4.
Role of Plant Biota
The role of plants is discussed as well as the species of different aquatic plants that occur in the dams of
Technopark.
Aquatic plants provide many attributes to a dam, such as a hiding place for insects and fish, food source for
organisms, nutrient sinks, oxygen supply and aesthetic enhancer (Verdouw, 2008).
The submerged segments of aquatic plants provide habitats for micro and macro invertebrates. These
invertebrates are in return used as food by larger fish and wildlife species including ducks. As aquatic plants
die, they are decomposed by fungi and bacteria to provide food for many other aquatic invertebrates (Masser,
2010).
Aquatic plants also act to eliminate or inhibit other organisms by different chemical means, for instance by
means of oxygen control (O’Brien et al., 1972). Therefore it could be said that higher plant abundance would
have a more intense affect on the surrounding elements.
The densest populated species that occur in the Technopark water system is the Cattail (Typha capensis) which
is superior in removing ammonia from effluents. The presence of plants and the type of plant can make a
significant difference in ammonia removal efficiency. (Gersberg et al., 1986).
Low effluent (NO2-+ NO3-)-N levels in the vegetated beds would indicate that the nitrified ammonia in this
system must have later been denitrified, and lost from the system as gaseous N2 or N20. Gersberg et al. (1983)
proved that denitrification is promoted when adequate dissolved carbon is present. No other mechanism besides
the sequential nitrification-denitrification, could explain nitrogen loss for reeds and bulrush (Gersberg et al.,
1986).
Hansen and Andersen (1981) demonstrated that the potential nitrification rate in sediments from a reed was
much higher than for sediments without plants from deeper waters. This evidence confirms that nitrifying
bacteria can directly be stimulated by the oxidizing abilities of rhizomes in plants. Gersberg et al. (1986)
explain that the shallower the root zones of an aquatic plant, the poorer the performance of ammonia removal.
Native plants are much more desirable than invasive varieties and therefore non native plants should be
removed. Invasive species out compete other indigenous species for nutrients, light and area. The invasive
species are normally not affected by the same threats and disease as native species. Non native plants are also
fast growers and since they do not have other pressures keeping them in check they can easily overgrow dams.
The key to a successful dam is to balance and prevent one specific aquatic plant from overtaking an entire dam
and to maintain diverse plants within a dam since it is healthy for the ecosystem (Verdouw, 2008).
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Free floating plants usually have leaves that float with a root system that hangs below the plant to filter the
water for nutrients. Water lilies, such as these in the Technopark dams are considered more desirable floating
aquatic plants, since they enhance the aesthetics of the area, if controlled (Verdouw, 2008).
An excess of submerged aquatic plant species exist, that has a root system that is generally attached in the
bottom sediment. These submerged plants require water for physical support. Most of the time the difference in
desire for these submerged plants is of personal taste and balance ability (Verdouw, 2008).
The roots of the lilies may cause to be obstacles for some of the aquatic birds.
1.5.
Role of Animal Biota
The surrounding bird species not only feed on the aquatic plants but introduce nutrients and sediments to the
dams. Each bird species contribute in its own manner to the ecosystems of the dams.
The fish that were primarily introduced were tilapia. If any bass was introduced, there would have been no
Tilapia left since Largemouth bass feed on Tilapia species that are present in the dam (McGinty, A.S. 1985).
Nile Tilapia (Oreochromis niloticus) has become one of the world’s most important domesticated fish, and is
widely cultured over Africa. Tilapia has a high tolerance to poor water quality and eats a wide variety of natural
food organisms. These fish are unable to withstand water temperatures lower than 10°C. Tilapias, stop feeding
at temperatures lower than 17°C and reproduce best at 27°C. Unlike most commonly farmed freshwater fish,
tilapia is very tolerant to high water temperatures, high ammonia and salinity concentrations as well as low
dissolved oxygen levels. Tilapia can survive routine dissolved oxygen concentrations (DOC) of less than 0.3
mg/L, although DOC should preferably be maintained at levels above 1 mg/L. Tilapia generally survive pH
levels between 5 and 10 but thrive in pH ranges of 6 to 9. These factors explain why the Nile Tilapia would
easily establish and reproduce in the Technopark dams and why they would not die under this undesirable
conditions. Their high numbers can be ascribed to them reaching sexual maturity at early stages and small sizes
(Popma & Masser, 1999).
Tilapia are nest builders, excavating them in the bottom of a dam with water shallower than 1m. Males usually
build the nest, thereafter mating with several females. Tilapia diet consists of aquatic macrophytes, larval fish,
plankton, detritus, benthic and planktonic invertebrates as well as decomposing organic matter. When tilapia
feeds, it does not disturb the dams’ surface as aggressively as carp, which imply that the bottom bentonite layer
would not undergo high damage with the occurrence of tilapia (Popma & Masser, 1999).
Like all other organisms, aquatic organisms and fish require oxygen to grow and survive, although it is needed
at a lower level. Diffusion adds dissolved oxygen at the interface of water and air, through the process of
oxygen production, such as photosynthesis.
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A common occurrence is that the amount of natural oxygen is not enough for the total demand of the dam. In
dam ecosystems, different organisms depend on varying oxygen needs. Typically, larger organisms have higher
oxygen demands, which would likely be the fish. This means that the tilapia would be the first to suffer during
low periods of oxygen (Verdouw, 2008).
2. Water Quality
Water sampling and testing only occurred in on two dams, since it is a costly process. The decision of specific
dams tested was made on their physical appearance and position in the water system of Technopark. Dam 6 was
chosen since physical removal of plants occurred on the dam and indicates bentonite disruption. The reason to
test dam 8 was because of its natural physical state, with dense aquatic plant cover and silt occurrence along
with fish presence.
Quality control procedures were followed for the chemical analyses and showed results within the confidence
interval. Results can thus be seen as accurate (Foit, 2011). Results will be explained hereafter (3).
Table 1 Indication of ideal water quality according to Williams & Zimmermann (2010).
Table 2
Sample
Dam 6
Dam 8
Dam 4
TOC
(mg/L)
DOC
(mg/L)
DO
(mg/L)
11.3
10.7
8.9
10.6
7.8
0.68
7.43
pH
5.62
6.19
EC
Turbidity
(μs/cm) (FAU)
79.1
115.1
55
17
Table 2 indicate the Total Organic Carbon (TOC), the Dissolved Organic Carbon (DOC),Dissolved Oxygen,
pH, Conductivity (EC) and Turbidity of dams 6 and 8. Dissolved Oxygen was tested in the field using a
dissolved oxygen meter. All other tests were completed in a laboratory, using 1L samples. DO was also taken
for dam 4, since it is the entry point for water into the Technopark water system and would provide a
benchmark for the system.
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12
10
8
Dam 6
Dam 8
Dam 4
6
4
2
0
TOC (mg/L) DOC (mg/L) DO (mg/L)
pH
Figure 1 relationship of Carbon, Oxygen and pH levels
The relationship of the total organic carbon, dissolved organic carbon, dissolved oxygen and ph is graphically
indicated in figure 1 for easy comparing.
140
120
100
80
Dam 6
Dam 8
60
40
20
0
EC (μs/cm)
Turbidity (FAU)
Figure 2
Figure 2 illustrates the relationship of the Conductivity and the turbidity of the two dams. Conductivity in dam
8 is much higher, although it has a much lower turbidity level than dam 6.
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Table 3
indicate the nitrate and phosphate levels of the two dams
Sample
NO₃-N NO₃ NH₄-N NH₄
PO₄-P
PO₄
P₂O₅
(mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)
Dam 6
1
4.2
<0.01
<0.01
0.06
0.2
0.14
Dam 8
1
4.2
<0.01
<0.01
<0.05
<0.2
<0.11
3. Problem summary :
Currently, the results are being studied and compared to ideal results by professionals, amongst others a
limnologist. During conversations with ecologists from Stellenbosch University and Working for Wetlands
independently, the results seem to indicate excellent conductivity levels for dams. They also pointed out that
nutrient levels may be high, but further investigation will confirm this statement. Turbidity is high in dam 6,
which was previously worked on, which may also indicate disturbances of the bentonite. pH levels of dam 6 is
lower than preferred, but acceptable (Williams & Zimmermann, 2010).
The turbid water prevents sunlight from reaching the submerged plants in the dams. Turbidity is not bad if the
dams are overrun by weeds, although most turbid ponds do not have many aquatic plants. The reason therefore
is that the turbidity of the water is caused by bottom sediments combined with the water column (Verdouw,
2008). The physical removal of the plants in dam 6 led to the disturbance of the bentonite surface and indicates
high turbidity as described above.
If the cloudiness was caused by organic growth, the organisms could be treated, but since the turbidity is caused
by bottom sediments, it would be a waiting game (Verdouw, 2008). There are however some products available
that would help the process to remove cloudiness, such as the products of the company Organic Water
Solutions1 and Henchem.
Since there is no continuous flow, each dam has established and is maintaining its own isolated micro
ecosystem. At this stage it is too early to proclaim that the nutrient, nitrate and phosphate levels exceed that
considered favorable for fish and other aquatic life.
1
- http://www.ows.co.za/
4. Usual Problems
In order to prevent common problems that affect dams and still freshwater systems, a few examples are
mentioned to be aware off and avoided.
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Human augmentation and use of natural resources unavoidably affect important ecosystems through the water
cycle process. Water must therefore be considered as vital to long-term, sustainable development.
Unfortunately, water resources are finite, and should be protected as far as possible (Falkenmark, 1986).
Some common problems most dams face is the filling of sediments, cracked or failing concrete, sliding or
sloughing earth, failing spillways, new gullies in filled dams and with the increase of people more safety
hazards exist.
Most biodiversity of lakes and pond ecosystems are threatened by human disturbances. The most important
threat is the increase of nutrient load, contaminations, invasion of exotic species and acid rain. Trends in
analysis have indicated that common biodiversity threats such as acidification, autrofication and contamination
by organic chlorines in older systems may become less of a threat. Other new threats that will become more
important include endocrine disruptors, ultraviolet radiation, global warming, and especially the invasion of
alien species (Brönmark & Hansson, 2002).
Habitat fragmentation is another great influence to still water problems. Developing a system with fragmented
habitats, or in this case fragmented micro-ecosystems may cause many problems, as noticeable. Obvious habitat
restoration deficiencies involve protective and riparian vegetation that result in weakened bank stability,
increased bank erosion predictions, consequences of stream channelization and moderate downstream siltation
(Price &Birge, 2005).
Further problems include important solute and silt flows that create massive water quality problems, most of
which are generated from current land use practices. Plant production water and joint use of water resources in
international river basins may require new approaches to water conservation and management.
The present approaches to water management disregard possible natural constraints including water availability
and quality. Surrounding soil degradation can affect or are affected by disturbances of the hydrological cycle,
water logging, salinisation and the absence of proper leaching and draining facilities (Falkenmark, 1986).
5. Recommendations
There are many ways to start removing aquatic plants from a water system, but if unplanned and ignorant
decisions are made it can lead to an economic catastrophe with major ecosystem implications. The bentonite
surface of the dam is an important determining factor for the method of plant removal. Some methods of
removal and restoration are sceptically discussed below in order to obtain the best possible solution. The
restoration of the dams includes the removal of plants and silt for the dams, if necessary. Most of the mentioned
recommendations refer to the vegetation of the deeper water, more to the center of the dam, such as the lilies
and the cattail.
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5.1.
Physical and Mechanical techniques
The most obvious manner of removal is physical of nature. By removing aquatic plants by hand, pulling it out
is in some cases fast and thorough but labour intensive. This manner of removal is however dangerous for
bentonite dams, as their structure will get damaged. Since not all plants should be removed, it would be
important to assign a percentage of removable plants.
A more mechanical way to restore the dams is by excavation. Using an excavator to remove the vegetation
from the dam would be fast, less labour intensive and thorough. The primary consequence of excavation is the
high disturbance on the surrounding vegetation and the ecosystem. Excavation will also harm the bentonite
surface of the dam. Even if the excavation can occur on the top of the dam, removing the leaves and silt, the
weight of the heavy machinery will produce trenches and leave the area around the dam in a weakened
condition. Furthermore, this operation is quite expensive (Dyer et al., 1974).
Using a rake, shovel or your bare hands works well to remove weeds near shorelines and in shallow dams, since
selective removal of individual plants can take place to keep desired species in check.
Making use of physical or mechanical techniques will require that there should be certainty that all the plant
fragments are removed from the pond. Most aquatic plants may re-sprout from small segments, therefore the
cut fragments should also be removed if possible. Although physical and mechanical methods may be difficult
without harming the dams, it is a good maintenance technique (Verdouw, 2008).
5.2.
Dredging or flushing
Dredging is considered to be a physical method of removal. Physically removing or digging sediment from the
bottom of the dam is known as dredging. Dredging may include a number of different results. Through
dredging the dam will become deeper, remove nutrient rich, organic sediments along with the plants growing in
the sediment. The process of dredging is very effective if executed correctly, although it is labour intensive and
expensive due to the heavy equipment. With the increase of the water column through dredging the plant life
will struggle to support itself with low levels of sunlight reaching the lower areas of the water column. Nutrient
removal allows the dam to be renewed or make it ‘younger’ (Verdouw, 2008). The main problem with dredging
is that it will definitely cause destruction to the bentonite layer, which will cause leakage and waste water.
Flushing raises the water level above its normal level, washing many unattached, floating aquatic plants out of
the pond. This may include intensive and large responsibility, especially since water need be used sparingly.
Flushing the water has two benefits. First, flushing out the nutrient filled water with nutrient free water will
help to reduce the existing plant growth, lower the overall nutrient content in the water and prevent future
growth (Verdouw, 2008).
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Altering the water level such as flushing will have negative effects on aquatic plant health since each species
has a preferred water condition such as water level. Sunlight will be unable to fully reach certain areas if water
levels are raised above a certain point leading to vegetation dieback because of a lack of sunlight (Verdouw,
2008).
If the water levels are dropped an equal affect will be achieved as the air and sunlight will dry out areas along
the uncovered water boundaries. It is obvious that without water, aquatic plants will die. Previous practices has
indicated that periodic draining and cleaning leave filamentous algae behind, but with abundant sunlight, dry air
and no available water the algae will burn off. Water level alterations can be a large project, especially if there
is no drain installed, but constant water supply may ease the process (Verdouw, 2008).
Draining the water is a successful but expensive option to perform the necessary removal of water plant species
and to repair the dam. This time-consuming project may also influence the fish and birdlife of the area (Dyer et
al., 1974).
If the dams are going to be drained, the muck and decomposed organic matter might as well be removed.
5.3.
Bottom layer replacement
As the bentonite, in some cases are damaged the possibility exist to remove the bentonite totally and use
concrete for the dams surface. This possibility to fill the dams with concrete is expensive and success in the
long run is not guaranteed. Studies have proved that concrete deterioration is sure to exist especially due to
climatic and operational factors. Interaction between alkali and aggregates, incorrect selection and specification
of concrete requirements as well as poor quality of concrete preparation during execution of the work indicate
untrustworthy results, unless good research and caution is followed (Stol’nikov, 1969).
The underwater injection of bentonite slurry of adequate viscosity has previously showed success in repair and
should therefore rather be rehabilitated than replaced (Chapuis et al., 1992).
5.4.
Shading
All chlorophyll aquatic plants require sunlight for photosynthesis. By limiting the amount of sunlight that
reaches the water column will decrease the quantity of aquatic plant growth. Natural shading from trees and
shrubs or artificial shading can promote the obstruction of sunlight. Evidence exist that, if necessary shade can
limit predation of fish by herons and kingfishers. In hot summer months shading will allow cool water areas for
fish that prefer so (Verdouw, 2008).
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5.5.
Aeration
If more oxygen is added to the dams it would assist balancing the aquatic ecosystem, in affect raising the water
quality. Colder water will increase the ability to hold more dissolved oxygen (Verdouw, 2008), but as
mentioned earlier the tilapia rather prefer warmer, cool water.
Adding more oxygen to the water system will allow faster decomposition processes, which will turn the organic
sludge into carbon dioxide. This carbon dioxide will be ventilated into the air in a much faster way than with
normal water agitation (Verdouw, 2008).
Making use of machines such as propellers and fountains is a possibility to accelerate the process of aeration.
Several models and sizes of aeration equipment for different dams and their needs are available. Some aerators
agitate the water surface by floating or spraying and splashing water, for instance a fountain. Some models can
even manage water movement and directional flow that move and mix deep water. Fountains would be the best
option since it adds oxygen, water movement and adds a beautiful display feature (Verdouw, 2008).
5.6.
Nutrient removal
Some people enjoy having other wildlife in the vicinity of the dams, such as geese and other waterfowl. These
waterfowl however, supply nutrients with their waste to the water system. If these added nutrients are not dealt
with, the plants will exploit it and will lead to over populated dams, such as the case at hand (Verdouw, 2008).
By limiting the amount of nutrients introduced into the dams, will limit the growth ability and rate of aquatic
plants. This is usually a long, timely process that has gradual results since aquatic plants and algae usually
require small amounts of nutrients to thrive. The sludge on the bottom of dams is rarely used and generally
contains high amounts of nutrients (Verdouw, 2008).
Planting quick growing native plants, that can intercept nutrients, around the pond and use much of the
available phosphorus and nitrogen before it gets into the pond is a good way of limiting nutrients. This will in
affect serve as a biological control. Many varieties of terrestrial vegetation exist that will improve the aesthetics
of the dams while using the nutrients of the runoff. Desired aquatic plants that will use nutrients and beautify
the dams may also be introduced. A great aquatic plant is Chara since it uses a lot of nutrients and serves as a
hiding place and food source for fish and insects in the water (Verdouw, 2008). It would strongly be advised to
avoid the introduction of more plant species and most importantly invasive species.
Removing the decomposed organic matter or muck from the bottom of the dams (dredging) can be very
difficult without damaging the surface. Dredging will quickly remove nutrients from the system, but can be a
large project to undertake making it very costly (Verdouw, 2008).
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"Binders" can be used to assist nutrient removal. Aluminum Sulfate, or Alum, can be used as binders to clear up
muddy or cloudy water and remove phosphorus. A fairly new American product “Barraclear” is a product with
Alum, bentonite clay, and a buffering agent as active ingredients to prevent pH change. Barraclear binds to
water available phosphorous to starve the plants. The amount required is dependent on the existing levels of
phosphorous within each dam (Verdouw, 2008).
5.7.
Herbicides and chemical treatment
Chemical treatment options can also be a solution to nutrient and plant removal of over populated dams. The
success of removal by chemical action is determined by the type and concentration of chemical and its manner
of dispersion. Since some chemicals treat aquatic plants better than other, it is necessary to refer to a local
specialist in order to obtain the best solution.
Liquid treatments are normally the most effective type of application in shallow dams. Granular applications
are usually used in deeper dams, but can be effectively used for spot treatment. The most common chemicals
are diquat herbicides, fluridone herbicides and copper products (Verdouw, 2008).
Algae are usually controlled with copper. Unfortunately, depending on the water chemistry and dosage, copper
may be toxic to certain fish and frog species within the minnow family and salmonids. Copper would not be
toxic if the water has high alkalinity and hardness, but this does however limit coppers effectiveness. Granular
copper sulphate is most commonly used. Since copper has a good price and is a broadly effective planktonic
and filamentous algae controller, it is widely used in high dosages. Liquid chelated copper products can also be
used to control plankton and different types of algae. Bioaccumulation of sediment may occur with constant use
of copper products (Verdouw, 2008).
There is many other effective broad spectrum, systemic herbicides, but specialist opinions will be required
(Masser, 2010). Contact is currently being made to schedule a meeting with a frog specialist that has excellent
knowledge on non-harmful effective herbicides.
5.8.
Biological treatment
Biological treatments are commonly accepted as the most ecological manner of restoration. Introducing
organisms to a dam may prevent and control aquatic weed growth. Other plant species, plant eating fish or
bacteria are commonly used as biological treatments. Biological control is a timely process in relation to most
other treatment methods; nonetheless it can be very effective and may be long term solution to the problems.
On a small scale, this method will be very successful, unless invasive organisms are introduced. Lake
management professionals should be contacted before organisms are introduced into the dams (Verdouw,
2008).
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Introducing more desired aquatic plant species can assist to reduce irritant species. Since native plants is in
check and balance with the local environment and would not disrupt any system they would be a good choice.
The task can be difficult considering that invasive species may be present and can out compete desirable native
species. Intrusive species should therefore be removed first (Verdouw, 2008).
Desirable indigenous plant eating fish or herbivores may also be introduced to restrain plant growth. Grass carp
is generally used to control certain aquatic vegetation. Some of the restrictions of grass carp are that they do not
eat all plant species as well as no algae. This infers that carp may lead to a shift from overpopulated vegetation
to an algae invested dam. If combinations of fish are used and aeration is intact, the algae may be controlled as
well. Luckily grass carp is bred sterile and will consequently have no reproduction in the dams. Their primary
and only function will be to eat (Verdouw, 2008).
Controlling aquatic plants with bacteria and fungi can also be applied successfully. Bacteria and fungi live on
various selective varieties of aquatic plants. If the correct microorganism is introduced the attacked plants will
die and more desired plant species will be unharmed and promoted (Verdouw, 2008).
5.9.
Organic Water Solutions
A local manner of chemically controlling the plants, algae and odour is by using Organic Water Solution
(OWS) treatments. OWS is situated in Somerset West and claim to be able to balance algae and nitrogen cycles,
flocculate Total Suspended Solids, increase Dissolved Oxygen, dissolve and digest sludge build up in the under
layer, break under layer waste down, disperse billions of colonies of positive anaerobic bacteria, reduce bad
odours and Ammonia production in the under layer. OWS also declare to be able to correct the ecological
balance in the under layer (http://www.ows.co.za/).
Although this is an attractive possibility, further research needs to be done on the method, concentrations and
possible consequences of this medium. These types of methods usually require continuous input.
5.10.
Fire
The earlier management plans did not recommend burning for several reasons that pose the questions; is the
area of the community ecologically fire-adapted? How much of this invasive plant is in the area or need to be
burned, and what is their fuel load? Will it be difficult to burn safely, and would the area be adversely affected
by the burning?
Lastly, since the area is situated in a residential, office area it presents potential safety and public relations
problems and requires consultation. Controlled burning still remains a possible approach if it can be done in
such a way as to avoid these problems above (Williams & Zimmermann, 2010).
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After any type of restoration or removal of plants it will be necessary to remove the cut weeds from all the
dams and place it far away in order to avoid them getting blown or washed back into the system. Try to stand
on the edge and rake the silt from the water surface closer to remove it and pick it up. The plant debris can even
be used as fertilizer for gardens (Verdouw, 2008).
Further research is required in order to recommend habitat change. By adding rooftop nests on some of the
buildings may attract more bird-life, which will feed on the plants, add nutrients and even feed on the fish.
6. Conclusion
As the Technopark dams have an abundance of nutrients, as noticeable in the dense aquatic vegetation, nutrient
removal will be necessary if the plants are not controlled otherwise. Treating algae and aquatic plants with
herbicides will kill them, but this would not remove the nutrients of the decomposing vegetation.
Physical removal does indeed remove large amounts of nutrients along with the living plant. The best way to
approach this is by raking or cutting the aquatic weeds and collecting the fragments that float around on the top
(Verdouw, 2008). It would strongly be advised to avoid the introduction of more plant species and most
importantly invasive species.
Although shading will result in plant decrease, it will possibly only affect the aquatic vegetation alongside the
shade and since it is the centre of the dams that are of interest, it would not be sufficiently supportive.
The possible herbicides mentioned in this study, are only a small number of the options and make it possible to
support the decision of the sort of herbicide to be used.
If dredging is considered, care should be taken not to harm the bentonite layer or the fish. The fish will have to
be caught in nets and transported to another sufficient water body. Fortunately there are enough dams in the
system for the fish. Will there be enough food in the specific dam? Will the fish stay there or will they be
returned to the original dam (8)? It is recommended to start rehabilitation from the lowest dam upward (in other
words from dam 9 up to dam 1).
OWS may be considered for dam 6. This may be a gamble and if the water starts to flow, it may affect the
whole system. This will also be a timely process in order to verify the results.
Throughout all the removal processes it is extremely important to confiscate the sediments as far away from the
dams as possible to avoid any fragment to get blown or washed back into the dams (Verdouw, 2008).
The removal of suspended solids, such as pollution, sedimentation, silt etc., should be a physical process rather
than biological. Biological processes such as microbial control and establishment of higher plants are usually
23 | P a g e
much more time consuming. Oxygen translocation will stimulate the nitrification of ammonia and the
breakdown of basic oxygen demands. This manner of treating artificial wetlands with reeds and especially
bulrushes saves money and energy (Gersberg et al., 1986).
After conversations and visits to Technopark with professional ecologists, the main subject mentioned was that
the key to removal would be to get the system running and that further decisions could be made thereafter.
Many abundant, undesirable aquatic plants thrive in shallow, stagnant water, as visible in dam 8 and would
change as water start to flow. Altering the water patterns of this stagnant water into a moving, continuous
riverine-like environment will increase the pressure of survival and growth of those aquatic plants. Additional
equipment could be necessary, but since these dams are already part of a water system it will require less effort
and cost if the flow of the water is restored. Water circulation creates directional flow and riverine-like
environments out of stagnant dams.
As explained in 1.4 (role of plants), it is essential to include aquatic plants to achieve a healthy dam ecosystem.
Planted systems function better than unplanted systems mainly for their nitrogen uptake. In the absence of
plants, oxygen can only be found in low concentrations in the top samples of up flow systems (Roger et al.,
1991).
According to Deon van Eeden, a well known Environmental Rehabilitation Practitioner and a partner of the
initial Technopark dam establishment team, the dams were designed to run ecologically. The specific design
with continuous water movement, water cascades, waterfalls and fauna is suppose to filter and aerate the water.
Initially only a few different plants were introduced to the system in low numbers.
If the circulation of the water system is active and running water is available, with movement down the
cascades and man-made waterfalls, aeration would increase drastically. This will increase the activity of the
fish and in effect raise their feeding ability.
Alternatively a certain percentage of Typha capensis (Cattail) in dam 1 and the s-channel as well as some of the
water lilies in dam 7 and 8 can be removed by spraying herbicide (recommend ConChem/Henchem) on the
leaves that are not submerged. After the plants are dead the plant matter should be cut off at a low level under
the water with scissors or sickles. It would not be advised to remove any aquatic plants by hand, which is
attached to the ground level of a bentonite dam.
It is difficult to recommend that removal should occur (e.g. Dam 1) since it may be accepted as an artificial
wetland. Professional service (or help) should be referred to with the onset of each restoration technique.
The rest of the plants in the dams seem to be under control. With further aeration of the continuous system after
repair, will help control plant populations in the dams.
24 | P a g e
Lower down at the channel linking dam 8 and 9, a definite separation should be established between the
Kukuyu grass and the stream itself. The aquatic plants in the channel should be kept as it is.
As noticeable, there are many possibilities and combinations that seem adequate, but further investigation along
with results of the repaired water flow and aerated system will indicate the proper removal methods. Qualified
experts in certain aspects might be needed in order to make a final decision on the specifications, such as
herbicides.
As this is just the draft, further investigations, interviews and time will lead to a better understanding of what
the system requires.
Acknowledgements
A great word of thanks for the assistance of Tony Ventouris, Marilie Carstens, Pieter van Heyningen together
with the TPOA for the opportunity, their motivation and support, whenever needed. Great thanks to Daniel
Kotze for his assistance with results and the water laboratory of Stellenbosch for the test and help with results.
Great gratitude to Me. Suzaan Kitzinger-Kloppers of the Botany and Zoology department of Stellenbosch for
her help, contacts and advise. Deon van Eeden, Heidi Niewoudt working for wetlands and Dr. Shane Jacobs of
the department of Conservation Ecology and Entomology of Stellenbosch University.
25 | P a g e
7. References
1) Keese, C. W. 1988. Sealing Ponds and Lakes with Bentonite. Inland Aquaculture Handbook, Texas Aquaculture
Association, p. A0704.
2) Stol’nikov, V.V., 1969, Durability of dams and Estimation of Their Behavior, Gidrotekhnicheskoe Stroitel’stvo,
No. 1, pp. 44-48 - http://www.springerlink.com/content/j465532672707187/
3) Chapuis, R.P., Lavoie, J., Girard, D., 1992. Design, construction, performance, and repair of the soil–bentonite
liners of two lagoons. Canadian Geotechnical Journal, Vol. 29, pp. 638-649
4) Dyer, N.D., Walker, R.W., Arrington, T.L., 1974. Earthen Dam Repair. United States Patent,
http://www.google.co.za/patents?hl=en&lr=&vid=USPAT3839871&id=5MczAAAAEBAJ&oi=fnd&dq=excavat
ion+dams&printsec=abstract#v=onepage&q=excavation%20dams&f=false
5) Fujii, N., Ichikawa, Y., Kawamura, K., Suzuki, S., Kitayama, K., 2003. Micro-Structure of Bentonite Clay and
Diffusion Coefficient Given by Multiscale Homogenization Analysis, Vol. 9, No. 2, Pp. 117 – 124
6) Verdouw, J., 2008, Water Quality solutions, Kasco Marine Incorporated. [Online] at
http://www.gotalgae.com/water_quality_solutions.htm Accessed on 31 May 2011
7) Ophardt, C.E., 2003. pH Scale, Virtual Chembook, Elmburst College. [Online] at
http://www.elmhurst.edu/~chm/vchembook/184ph.html . Accessed on 2 June 2011
8) O’Brien, W.J., DeNoyelles, F.Jr., 1972. Photosynthetically Elevated pH as a Factor in Zooplankton Mortality in
Nutrient Enriched Ponds. Ecology, Vol. 53, No. 4, pp. 605-614
9) Tchobanoglous, G.,1987. Aquatic Plant Systems for Water Treatment: Engineering Considerations. In Aquatic
Plants for Water Treatment and Resource Recovery. K. R. Reddy and W. H. Smith (Eds.), Magnolia Publishing
Inc., Orlando, Florida., 27.
10) Gersberg, R. M., Elkins, B.V., Lyon, S.R., Goldman, C.R., 1986. Role of Aquatic Plants in Wastewater
Treatment by Artificial Wetlands. Water Res., Vol. 20, No. 3, pp. 363 – 368
11) Rogers, K.H., Breen, P.F., Chick, A.J., 1991. Nitrogen Removal in Experimental Wetland Treatment Systems:
Evidence for the Role of Aquatic Plants, Research Journal of the Water Pollution Control Federation. Vol. 63,
No. 7, pp. 934 - 941
26 | P a g e
12) McGinty, A.S. 1985, Effects of Predation by Largemouth Bass in Fish Production Ponds Stocked with Tilapia
Nilotica, Aquaculture, Vol. 46, pp. 268-274
13) Popma, T. & Masser, M., 1999. Tilapia; Life History and Biology, Southern Regional Aquaculture Center. No.
283.
14) Adamis, Z. & Williams, R.B., 2005. Bentonite, Kaolin, and Selected Clay Minerals, World Health Organisation,
Environmental Health Criteria 231.
15) Van Eeden, D., 2011, Technopark dams, Personal meeting at technopark on 6 June 2011.
16) Foit, W., 2011. Chemistry of Water Samples. Central Analytical Facilities of Stellenbosch University
17) Williams, B. & Zimmermann, R.A., 2010, Analysis of Water Quality, Broad Brook Coalition, [Online] at
http://www.broadbrookcoalition.org/ Accessed on 8 June 2011
18) Masser, M.P., 2010. Aquaticplant; A Pond Manager Diagnostic tool. Texas A&M University. [Online] at
http://aquaplant.tamu.edu/ Accessed on 8 June 2011
19) Van Oudshoorn, F., 1999, Gids tot Grasse van Suider-Afrika, ens…..
20) Zaranyika, M.F., & Chirinda, T., 2011, Heavy metal speciation trends in mine slime dams: A case study of slime
dams at a goldmine in Zimbabwe, Journal of Environmental Chemistry and Ecotoxicology. Vol. 3, No. 5, pp.
103-115
21) Aukes, B., & AFAM, LLC.,2006. Koi Pond Water Quality, National Fish Pharmaceuticals. [Online] at
http://www.fishyfarmacy.com/koipond/water_quality.html Accessed on 8 June 2011
22) Wurts, W.A., & Durborow, R.M., 1992. Interactions of pH, Carbon Dioxide, Alkalinity and Hardness in Fish
Ponds. Southern Regional Aquaculture Center, No. 464
23) Johnson, S., 2009. Just What Do Nitrate and Phosphate do Anyway? APEC Water Systems. [Online] at
http://www.freedrinkingwater.com/water_quality/quality1/1-what-nitrate-and-phosphate-do.htm Accessed on 8
June 2011
24) Brönmark, C., & Hansson, L.A., 2002. Environmental Issues in Lakes and Ponds: Current State and Perspectives.
Environmental Conservation. Vol. 29, No. 3, pp. 290-306
25) Price, D.J., & Birge, W.J., 2005. Effectiveness of Stream Restoration Following Highway Reconstruction
Projects on Two Freshwater Streams in Kentucky. Ecological Engineering. Vol. 25, pp. 73-84
27 | P a g e
26) Falkenmark, M., 1986. Fresh Water: Time for a Modified Approach. Springer. Vol. 15, No. 4, pp. 192 – 200
27) Johnson, S.L., Adams, R.M., Perry, G.M., 1991. The On-Farm Costs of Reducing Groundwater Pollution.
American Journal of Agricultural Economics, Vol. 73, No. 4, pp. 1063-1073
28 | P a g e