Introduction to the study
Centurion Lake as the name implies is in Centurion, Gauteng. It is under the Tshwane Municipality. The location is shown in figure 1.
Figure 1: Location of Centurion Lake (Source: Google Maps)
The Hennops River flows into the Centurion Lake. The river begins near Kempton Park, east of Johannesburg. It is one of Gauteng’s most polluted rivers. The Centurion Lake water and surroundings will be compared with the Rietvlei Dam which is outside the built environment and it is therefore assumed has less pollution. Figure 2 shows the Centurion Lake from the Centurion mall side.
Figure 2: Centurion Lake
Research question: What impact do humans have on ecosystems in and near lakes?
Hypothesis: Humans have a negative impact on ecosystems in and near lakes due to the pollution that happens in and around lakes.
Motivation: Ecosystems are a vital part of the environment even for our own survival. The world itself is an ecosystem in which abiotic and biotic factors interact. I have chosen this particular topic to analyse if humans have that much of a negative impact on ecosystems.
Aim: To discover and to determine the ways in which humans affect/impact the biodiversity in ecosystems in and near lakes.
Literature Review
An ecosystem is a community of living organisms (biotic) such as insects and fish, and the non-living components of their environment, such as air and sunlight (abiotic). The biotic and abiotic factors interact with one another such that, what affects one element, affects the whole ecosystem.
Lake ecosystems can be classified as aquatic (water) ecosystems. There are two types of aquatic ecosystems that is, marine ecosystems and freshwater ecosystems. Lakes are classified under freshwater ecosystems.
Many lakes and wetlands are disappearing because of the ‘human hand’. Today lakes can be classified as endangered. Tim McDonnell (2015) has the view that overfishing is the reason why most lake habitats are dying out. James Owen, for The National Geographic (2015) has the same view that overfishing could cause for inland waters, such as lakes, to be neglected as the fish would ‘disappear’ and people would see the lake to have no use.
The carbon that humans release into the atmosphere through industries, car exhausts and even fires may lead to the formation of acid rain. Melvin Mencher (2017) argues that that acid rain, which is also caused by humans, is the reason why most lake habitats are dying. Even though both of these opinions/reasons are different, they have one thing in common; humans are the creators of these problems.
Lakes are a source of drinking water for cities and villages alike. The United States Environmental Protection Agency (EPA) found that both algae and high nitrate levels cause problems in sources of drinking water. These high nitrate levels are caused by the use of inorganic fertilizers, which contaminate the freshwater.
A Carte Blanche report revealed that South Africa has the highest known levels of blue-green algae contamination in the world, with about two thirds of our national water resource contaminated (Lombard, 2017). Analyzed water bodies revealed that between 2002 and 2012, 62% of water bodies had high levels of blue-green algae. The algae posed a high health risk due to surface scum.
According to Sarah Hicks, Kent State University(2016) the litter that humans produce get washed off into lakes and streams which cause a danger to the organisms living in the water. The different chemicals that are dumped in lakes by industrial companies explain the stench that come from the lakes.
Humans affect ecosystems in a variety of ways. BBC stated that human waste enters natural ecosystems where it can cause them to become unbalanced. Household waste (cigarettes, plastic bottles, plastic bags etc.), industrial waste (chemicals used in industries), agricultural waste (pesticides, inorganic fertilizers) and gases produced by burning fossil fuels are the main types of wastes produced by humans, which have a massive effect on ecosystems.
According to the Water Encyclopaedia (2017), in urban areas, trash and litter are dumped directly into a body of water, or deposited along riverbanks or lakeshores. It also stated that the trash also comes from people who fish or participate in other forms of water-related activities.
According to Milton Kazmeyer (2017) humans impact freshwater ecosystems in a variety of ways, such as through the construction of hydroelectric dams or irrigation projects and the overuse of water. He also stated something similar to that of Sarah Hicks, stating that the freshwater ecosystems near towns and cities are affected and are threatened by runoff pollution.
Water pollution can be managed in a variety of ways. Business Wales (2014) stated some practical ways to reduce water pollution. This includes being prepared for pollution incidents, putting in place measures to prevent uncontrolled releases or leaks from causing pollution and to store and handle materials in a practical way.
Jared Skye, BA Environmental Science, Stated three ways in which water pollution could be prevented. Firstly conserving soil, as the soil that is eroded into the water carries sediments into the water from the land, could be carrying pollutants. Secondly is to dispose of chemicals properly, including industrial chemicals and domestically used chemicals. Lastly is to clean up beaches and waterways by picking up litter and organizing cleaning parties.
Pollution is a major problem in all aspects of the environment, whether it is water pollution, land pollution, air pollution, noise pollution etc. Pollution needs to be addressed in order to protect a variety of ecosystems.
The biodiversity of freshwater ecosystems are on the decline. Humans affect the cleanliness of the water in a mostly negative way and this may cause for the species that live in the water to become endangered.
In order to manage pollution, Sarah Hicks, states that the following questions need to be asked:
1. What is the source of the pollution?
2. How much pollution is occurring?
3. What is the projected lifetime of the pollution?
4. What are the expected effects of the pollution?
Methodology
Centurion Lake
Observation and water analysis
Observation will include photographs and analysis will involve the collection of water samples at the site,
- Observe the amounts of litter and the types of litter in and near the lake
- Observe the surrounding area of the lake
- Note the smell of the water and surrounding area
- Collect water samples from different areas of the lake
- Do a physical analysis of the Water samples ( test for ph levels using litmus paper and observe the contents inside the water)
- Conduct a map study of the course of the river that flows into the lake, The Hennops River.
Rietvlei Dam
Observation will include photographs and analysis will involve the collection of water samples at the site,
- Observe the amounts of litter and the types of litter in and near the dam
- Observe the surrounding areas of the dam.
- Note the smell of the water and surrounding area.
- Collect water samples from different areas of the dam.
- Do a physical analysis of the Water samples ( test for ph levels using litmus paper and observe the contents inside the water)
- Conduct a map study of the course of the river that flows into the dam, Sesmylspruit River.
Presentation of data
Data collected will be presented using tables and various types of graphs.
o Table: Tables are used to directly compare sets of data using rows and columns. This will directly compare the Centurion lake to the Rietvlei Dam
Centurion Lake Rietvlei Dam
o Bar Graph: Will be used to show the pH test results
o Maps: Will be used to show the course of the rivers that flow into the dam and the lake.
Results
Data Collected:
Centurion Lake:
‘ The Centurion Lake has an excessive amount of litter. This includes bottles, food rappers, cigarette butts and sewage.
Figure 3 Centurion Lake pollution (Source: Author)
‘ The lake is surrounded by a lot of human activity as it is surrounded by business centres such as the Centurion Mall and Gautrain Station. The surrounding areas also contain large amounts of litter.
Figure 4 Surrounding Areas of the Centurion Lake (Source: Author)
‘ The lake had a pungent smell. The smell was foul and it smelt of sewage. The bad smell came from the water.
Figure 5 the Centurion Lake Waters (Source: Author)
‘ Two water samples were collected from the lake. The water looked particularly clear but had small brown particles in it. The water samples had a pungent and unpleasant smell.
Figure 6 Water samples that were collected from the Centurion Lake (Source: Author)
‘ A more accurate ph. test would have been conducted but I was unable to find proper litmus paper to conduct the tests. The pH test would have seen if the water from the dam and lake were suitable for wildlife to live in or suitable for human consumption. Without proper litmus paper I used pool water testing paper in order to find out the pH of the different water samples and thereby determine whether the acidity of the water is harmful to humans or the wildlife that live in and near the water.
Figure 7 Centurion Lake water pH test (Source: Author)
Water should be neutral (have a pH of 7) according to international standards.
The following pH chart was used to rate the pH of the water:
Figure 8 pH chart (Source: Precision Nutrition)
‘ The sewage that gets into the river causes unnatural foam to be formed on the river. The Hennops River is fed by tributaries and these tributaries already contain pollution when they reach the Hennops River. The Kaalspruit River that passes through the Tembisa Township has a lot of pollution as residents in the high density area often through their domestic waste into and along the river. The extremely polluted Kaalspruit River feeds into the Oliefantspruit River, which then flows into the Hennops River. Figure 7 shows the Hennops River with the unnatural foam.
Figure 9 the Hennops River (Source: Author)
‘ Figure 8 is a map that shows the tributaries to the Hennops River. The tributaries as the River mentioned above passes through polluted areas, homes and industrial, thereby polluting the Hennops River before it flows into the lake.
Figure 10 Hennops river and tributaries (Source: Google Maps)
Rietvlei Dam:
Observations and recordings at the Rietvlei dam:
‘ There was not a sign of litter at the dam. The dam itself and the surrounding area were clean and there was no sight of litter or sewage.
‘ There were animals that live in the dam as well, unlike in the Centurion lake where there were no animals. The animals included tadpoles, fish, ducks and crocodiles. The Rietvlei dam and its surrounding are shown in Figure 9 below.
Figure 11 Rietvlei Dam and surrounding areas (Source: Author)
‘ The surrounding areas of the lake are quiet and clean. There is not much human activity except for the people that are fishing and camping. Limited number of people and activities around the dam may also mean minimal disturbance to the lake’s ecosystem and surroundings.
‘ The nature reserve that the dam is situated in is protected, which contributes to the cleanliness of the dam as there are strict rules put in place for people who are visiting.
Figure 12 Surrounding areas of the Rietvlei Dam (Source: Author)
‘ There was no foul smell in the area. The air smelt fresh and there were no pollutants in the air.
‘ The water itself smelt unusual. It was not a bad smell but it was a smell that I am not used to water smelling like.
‘ The water contained natural elements such as algae and tiny twigs. The water looked suitable for wildlife to live in.
‘ Two water samples were collected from different parts of the dam. The water looked clear and did not have an unpleasant smell.
The water had algae and very small twigs in it. Figure shows the water collected from Rietvlei Dam.
Figure 13 Water Samples collected from the Rietvlei Dam (Source: Author)
‘ A more accurate ph test would have been conducted but I was unable to find proper litmus paper to conduct the tests. The pH test would have seen if the water from the dam and lake were suitable for wildlife to live in or suitable for human consumption. Without proper litmus paper I used pool water testing paper in order to find out the pH of the different water samples and thereby determine whether the acidity of the water is harmful to humans or the wildlife that live in and near the water.
Figure 14 Rietvlei Dam water pH test (Source: Author)
Water should be neutral (have a pH of 7) according to international standards.
The following pH chart was used to rate the pH of the water:
Figure 15 pH chart (Source: Precision Nutrition)
‘ The Rietvlei dam is ‘fed’ by the Sesmylspruit River. This river does not flow past many residential areas. The river does not bring in much debris into the dam.
‘ Because the dam is in a nature reserve any garbage that gets into the dam from the river gets cleaned up by the people who protect the reserve.
‘ Figure 12 and Figure 13 shows the Rietvlei dam and the River which flows into it. The River passes through a nature reserve which is kept free from most pollutants.
Figure 16 Rietvlei Dam (Source: Google Maps)
Figure 17 Rietvlei Dam (Source: Google Maps)
Processing of information
1. Observations: Differences between the Centurion Lake and the Reitvlei Dam
Table 1: Differences between the Centurion Lake and the Rietvlei Dam
Centurion Lake Rietvlei Dam
‘ Excessive amounts of litter ‘ No litter
‘ Surrounded by a lot of human activity (e.g. business centres) ‘ Very little human activity present (fishing; camping)
‘ Foul and pungent smell ‘ Refreshing and odourless smell
‘ Clear water containing inorganic substances. Foul smell ‘ Clear water containing organic substances (algae; twigs). Pleasant smell
‘ No wildlife in the water ‘ Wildlife living in water.
Sources and course of the Rivers that flow into the lake and dam
Figure 18 Hennops River and tributaries (source: Google Maps)
The Centurion Lake is not only polluted by its surrounding areas but also from the other rivers that is connected to. Such as the Kaalspruit River that flows through Tembisa, a high density township. The pollution from Tembisa goes into the Kaalspruit River then into the Oliefantspruit River, then finally into the Hennops River where it reaches the Centurion Lake.
Figure 19 Rietvlei Dam and Sesmylspruit River (Source: Google Maps)
The Rietvlei Dam is fed by the Sesmylspruit River, because the river does not pass through densely populated not much pollution gets into the lake then into the dam. And because the dam and the river flow in a nature reserve, there are people that clean any signs of pollution. There is also a water treatment plant in the reserve which serves to cleanse the water.
2. pH of the water
Table showing the pH of the water samples collected from the Centurion Lake
Acidic pH Alkaline pH
Sample A 3.0 9.0
Sample B 2.0 10
As can see in the graph, sample A has an acidic pH of 3 and alkaline pH of 9 and sample B has and acidic pH of 10 and alkaline pH of
2. Both of the samples are far from being neutral and this shows that the water in the Centurion Lake is harmful to humans and other wildlife. The sewage and garbage in and around the lake cause for ecosystems in the lake to not be able to survive.
Table showing the pH of the water samples collected from the Rietvlei Dam
Acidic pH Alkaline pH
Sample A 3.0 7.0
Sample B 2.0 7.0
As can see in the graph, sample A had an acidic pH of 3 and alkaline pH of 7 and sample B had an acidic pH of 2 and alkaline pH of 8. This shows that the water in the Rietvlei Dam is more or less neutral and because of this ecosystems are able to survive as there is not much human influence to damage the lake and surrounding environment, unlike at the Centurion Lake.
o Because of all the pollution that humans cause the chemical properties in the water change making it unfit for ecosystems in and around the lake to survive.
3. Water Analysis
The water samples were to be sent for analysis to an analysis centre, but it was too costly. This would have given an in depth comparison between the water from the Centurion Lake and the water from the Rietvlei Dam. A physical and chemical comparison would have been done. After the water samples were going to be analysed, below is a quotation from the UIS Analytical services explaining the ways in which the water samples would have been tested.
Conclusion
Where human activity is present there is usually pollution which affects the ecosystems, such as lakes and others in the surrounding area. This was out in the comparison between the Centurion Lake and Rietvlei Dam.
The Rietvlei Dam is situated in a nature reserve where there is barely any human activity except for the few people who fish or camp. The water is clean and there is no sign of land or water pollution. There is wildlife present in the lake such as ducks, fish and crocodiles which shows that the lake and surrounding areas are suitable for wildlife and for ecosystems to survive.
Unlike at the Centurion lake where there is a lot of human activity as it is surrounded by industries and business centres such as the Centurion Mall and Gautrain Station. The lake had sewage and garbage in it. When the water samples were collected the water looked clear but it had a pungent smell and had small, unnatural particles present in the water. There was no wildlife present in and around the lake. The lake also gets its pollution from places where the river flows past such as the densely populated township of Tembisa.
Humans affect ecosystems in and near lakes as they contribute to land and water pollution through littering and sewage waste. All these pollutions affect the water and surrounding areas destroying ecosystems.
Because of all the pollution that humans cause the chemical properties in the water change making it unfit for ecosystems in and around the lake to survive.
Bibliography
- BBC. 2014. Ecosystems, how do humans affect ecosystems? Retrieved 6 March 2017http://www.bbc.co.uk/schools/gcsebitesize/science/triple_ocr_21c/further_biology/ecosystems/revision/4/
- Business Wales. 2014. Preventing water pollution. Retrieved 23 April 2017 https://businesswales.gov.wales/preventing-water-pollution
- James Owen. 2005. Overfishing is emptying world’s rivers and lakes. Retrieved 6 March 2017 http://news.nationalgeographic.com/news/2005/12/1201_051201_overfishing.html
- Laetitia Velleman. 2013. Lake Stench Now Unbearable. Retrieved 5 March 2017 http://rekordcenturion.co.za/11336/lake-stench-now-unbearable/
- Melvin Mencher. 2017. Dying Lakes. Retrieved 4 March 2017 http://highered.mheducation.com/sites/0073511994/student_view0/nrw_plus/chapter3/dying_lakes.html
- Milton Kazmeyer.2017. Human impacts on freshwater ecosystems. Retrieved 23 April 2017 http://sciencing.com/human-impacts-freshwater-ecosystems-23308.html
- Sarah Hicks. 2016. Pollution. Retrieved 6 March 2017 http://www.lakescientist.com/pollution/\
- Tim McDonnel.2015.Overfishing. Retrieved 4 March 2017 http://www.motherjones.com/environment/2015/01/climate-change-lake-victoria-overfishing
- United States Environmental protection agency. 2016. Where this occurs: Lakes and Rivers. Retrieved 5 March 2017https://www.epa.gov/nutrientpollution/where-occurs-lakes-and-rivers
- Water Encyclopaedia. 2017. Pollution of streams by garbage and trash. Retrieved 6 March 2017 http://www.waterencyclopedia.com/Oc-Po/Pollution-of-Streams-by-Garbage-and-Trash.html
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