Conservation Biology

Thursday, March 08, 2007


Rietvlei Dam Nature Reserve is one the grassland urban reserve on the central South African highveld [1]. Apart from being grassland, on the other part of the reserve there is a peat wetland which provide habitat to aquatic plant and animal species. There are number of plants and animal species that are found within the reserve. Exotic species such as blue gums are found. The dam on the reserve is very important source of water for Pretoria and the surrounding areas. Rietvlei Dam, situated on the Hennops River, has been a source of water supply to the city of Pretoria since 1933 [2].

On the reserve, there is a peat wetland. The wetland of the reserve is regarded as a good asset [3]. This wetland plays an important role in purification system of water thus improving water quality. This is because the reeds and other plants in the wetland slow down the water movement and there by suspended solids materials are settled out before they can be deposited into the dam. . The presence of this wetland; minimize the cost of cleaning water, which normally involves expensive cleaning chemicals. Water flow is slowed by vegetation where the suspended solids are settled out. These biological processes remove heavy metals and toxic substances.

Pollution is a serious problem facing Rietvlei dam nature reserve. Pollution can be defined as the chemical or physical agent in an inappropriate location or concentration [4]. It involves the introduction of substances and any form of energy in the environment. Pollution can be natural or human induced i.e. naturally through volcanic eruptions and human activities such as construction, minerals extraction and transportation are sources of pollution. Three main components of the environment tend to be affected by pollution – air, water, and land or soil. [4]

There are different sources of pollutants that tend to affect the Rietvlei dam nature reserve; agricultural fields, airport and human settlement and development projects. The first one is the fact that on the eastern and southern part of the reserve, the area is used for agricultural purpose. The use of crop residues, manure and pesticides, tends to contaminate water – these pollutants are introduced into water bodies as a result of surface run-off. Once they are in the water body, they are distributed far and wide through the movement of water. In non-flowing water body, pollutants decrease the water level. The use of nitrogenous fertilizers results to nitrite contamination of drinking water. [4]

Rietvlei dam nature reserve is found some few kilometres away from Johannesburg international airport and it is close to the R25 high way [1]. The aircrafts and motor vehicles are the main source of particulates that result in air pollution. These particulates are released into the atmosphere. When they are in the atmosphere, they are dispersed to different points away and they are then deposited in the water bodies (Rietvlei dam). They are normally deposited in form of wet deposition or precipitation. When these are deposited into the water body, they pollute water there by disturbing aquatic ecosystem. Contaminated water become unsuitable for human consumption and may cause diseases such as cholera. [4]

Rietvlei Dam nature reserve is located next to the human settlement (Centurion) [3]. Land pollution is very serious problem in the area surrounding Rietvlei dam nature reserve. This includes biodegradable, combustible and non-combustible waste. Household waste such as kitchen refuse, plastics, bottles and metal objects are discarded everywhere. After they are just discarded, they end up in the dam (Rietvlei) polluting the water.

Contaminated water threatens human health through the direct consumption. These may cause diseases such as cholera. Contamination of water bodies has impact on aquatic ecosystem. The enrichment of nutrients into water may lead to algae which may shade streams. When the biodegradable organic matters are discarded into the water, the oxygen content is reduced and water becomes dark. [4]

Management of solid waste can be done in variety of ways, this includes land filling; where refuse are collected from the source point and then dumped in pit or a trench. The pit or trench must be properly designed and prepared; this will ensure its long life span. After dumping the waste can be compressed and compacted. Composting can be the other way of reducing waste. It is the process whereby there is induced decomposition of biodegradable waste to produce special humus known as compost. This compost can be used as manure, soil conditioner and reclamation of hills and gullies.

Air pollution can be addressed by enforcing air pollution standards or clean air amendments act, there by setting emission standards. For machinery manufactures, they have to be mandated to install exhaust control or less polluting engines [4]. The strict punishment in form is needed to offenders. Raising electricity and gasoline rates will discourage waste and inefficiency. [4 and 5]

Awareness campaigns are essential in order to educate the public about the importance of the Rietvlei dam nature reserves in water supply. It is important that all activities including human development projects, farming or settlement not allowed next to the reserve.


1. Southern African birding cc. Rietvlei Dam Nature Reserve. [Internet]. Accessed 2007 Mar 06. Available from:

2. Toerien, D.F and Walmsley, R.D. (1979). The Chemical Composition of the Upper Hennops River and its Implications on the Water Quality of Rietvlei Dam.
Water S.A. Vol 5, No.2 p77-89. Available from

3. Rietvlei nature reserve: Historic background. [Internet] [Accessed on: 2007 Mar 06]. Available from:

4. Encyclopedia of Public Health information about pollution [Internet] Encyclopedia, The Gale Group, Inc. Available from:

5. Bascon, R. (1996) Health effects of outdoor air pollution,
American Journal of Respiratory and Critical Care Medicine [Am. J. Respir. Crit. Care Med.]. Vol. 153, no. 1, pp. 3-50. 1996. Available from:

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