RESEARCH DESIGN AND METHODOLOGY
Five (5) water users were identified as the possible main contributors/ polluters in the catchment, namely mines and tailing dams, industries, sewage works, agricultural activities, and some settlements. To establish the water quality impact, water samples were taken at strategic points along the Blesbokspruit (which empties into Vaal River at Vereeniging downstream of the Vaal Dam). The study site selected is the Blesbokspruit that drains into the Vaal River at Vereeniging, downstream of the Vaal dam and upstream of the barrage. The Vaal dam and the Barrage are Rand Water’s abstraction points. Water abstracted at these points is treated for potable use and supplied to the whole of Gauteng as well as some parts of the Free State and North West Provinces.
Description and Overview of the Catchment
Location, area and size
The Blesbokspruit runs from Benoni in the East Rand part of the Ekurhuleni Metropolitan Municipality (EMM) to Heidelberg in Lesedi Municipality, Gauteng Province. This study focuses on the Lower Part of the Blesbokspruit, i.e. from Springs to Heidelberg. The study area, Lower Blesbokspruit flows in a southerly direction past Springs where the two branches (Klein Blesbokspruit) join up north east of springs and just north of Grootvlei Mine. Upon entry of the Grootvlei mine water, another ERWAT Water Care Works (WCW), Ancor, discharges effluent further downstream to the Blesbokspruit wetland system. The Blesbokspruit then flows almost due south for about 30 km, after which it flows due west through Nigel, and then through Heidelberg, passing through Heidelberg and Ratanda, and picking up the treated effluent discharge from Tsakane WCW, Grundling WCW, Herbert Bickley WCW, Heidelberg WCW and Ratanda WCW (SRK, 2008). The Blesbokspruit catchment is highly altered due to urban, industrial and mining development. These developments have significantly affected water quality, flow and water level regime, as well as altering stream morphology. All of these effects have impacts on beneficial water use along the Blesbokspruit itself and Vaal River. As far as its sub-regional context is concerned, the catchment is traversed by three national roads, namely the N17, N12 and the N3, which create certain potentials in terms of future economic development.
Geographical and Climatic Description of the Study Area
The average annual rainfall in Ekurhuleni Metropolitan Municipality is 670 mm recorded over a period of 31 years (Madden, 1987). Hailstorms are uncommon and snow falls occur on rare occasions. The average annual rainfall in Lesedi Municipality is approximately 700mm, occurring mostly from November to March in the form of thunderstorms.
In Lesedi Municipality, the average annual surface temperature varies between a minimum of 4°C recorded during June and July and a maximum of 26°C recorded during January, with the lowest and highest recorded as – 8°C and 35°C respectively. In the Ekurhuleni Metropolitan Municipality (EMM), temperature vary from -10oCin winter to 35oC in summer. (http//www.wetlands.org/RSIS/-COP9 Directory /Directory /1ZA0 04.html)
Topography and Geology
Ekurhuleni Metropolitan Municipality (EMM)
The area underlying EMM has rocks that vary from Swazian to the Mesozoic Eras. The geology of the area is fairly simple and stable with underlying sedimentary rocks of Karoo and Transvaal age overlying formation of gold bearing Witwatersrand (Dini, 1999). The gold bearings reefs of the Witwatersrand Supergroup and Transvaal Sequence suboutcrop and outcrop along an arc in the East Rand Basin group which stretches from Benoni eastwards towards springs and then southward to Nigel (Barradas and Loggenberg, 1996). Outcrops of the Witwatersrand Reef occur in some areas within the Eastern Basin, at springs against the Transvaal Sediments. The Black Reef Quartzite Formation and the Malmani dolomites form part of the Transvaal sequence. The Grootvlei Mine is exploiting the Kimberly Reef of the Witwatersrand Supegroup and the Black Reef of the Transvaal Formation for Gold and other precious metals such as silver, osmium, rhodium, ruthenium, iridium and platinum (Digby Wells and Associates, 1996)
Lesedi Local Municipality
The Karoo Sequence consists of a vast accumulation, nearly 8km thick, of shale, sandstone, and mudrock with diamictite and tillite at the bottom and coal about halfway up. These rocks have been extensively intruded by dolerite in the form of dykes and sills. The Karoo sediments are represented in the study area by the Vryheid and Dwyka Formations. The Geology of the area is generally flat positioned sedimentary rocks of Karoo and Transvaal age overlying older formations of Gold bearing Witwatersrand. (Lesedi EMF, 2006)
Land Use and Vegetation
Land Use in the area varies from natural, agricultural, industrial, mining, urban and rural settlements as well as recreational and nature reserves.
– Natural: Marivale Bird Sanctuary
– Agricultural: Irrigated crops such as maize, vegetables, lucerne, lawn grass exist within the catchment and water from the Blesbokspruit is being utilized for irrigation. Animal watering exists in the catchment and also water from the Blesbokspruit is being utilized.
– Industrial and mining: The Witwatersrand Basin, made up of East, Central and West Rand Basins in South Africa is famous for its prolific gold, coal and uranium deposits and mining has been going on in the basin since the late 1800 (Handley, 2004). Records of water ingress into underground mines in the East Rand dated back to 1909 (Scott, 1995). Many mines in the vicinity discharge their polluted water into the Blesbokspruit, and the currently the largest and operational mine in springs discharges between 80 and 100Ml/d underground water into the Blesbokspruit (Schoeman and Steyn, 2000). There are also industries in the catchment that dispose their waste into the slimes dams which in turn pollute the Blesbokspruit.
– Urban and rural settlements: The towns of Boksburg, Benoni and Brakpan lie in the Northwest, Nigel located on the South, Springs in the East and Heidelberg on the southwest of the Catchment. There is a full sewage reticulation system in these towns and all of them discharge their effluent in the Blesbokspruit. The townships in the area are semi urban and are connected to the sewer system.
– Recreation and nature reserves: The Marivale Bird Sanctuary, in the southern part of the catchment covers approximately 100 hectares and is about 7.4km long. It attracts mainly birdwatchers and hikers. The Suikerbosrand Nature Reserve forms an enclave into the western edge of the Lesedi Municipal Area. This nature reserve is situated in the Suikerbosrand Hills which contribute substantially to the natural beauty of the area. The nature reserve is well managed and the eco system is fully protected in this area (Lesedi EMF, 2006).Vegetation
Ekurhuleni Metropolitan Municipality (EMM)
EMM falls within Sac’s Grassland Biome (Low and Rebelo, 1996). This grassland biome is one of the most threatened in SA, with 60-80% irreversibly transformed, while only 2% is formally conserved (Bredenkamp, 2002). The biodiversity status of the area includes two grassland vegetation types, according to Low & Rebelo (1996), namely Moist Cool Highveld Grassland (Bredenkamp and van Rooyen 1996b) and Rocky Highveld Grassland (Bredenkamp and van Rooyen 1996a); the former vegetation type covers approximately 55% of the area, while the latter covers 45%. The vegetation has an abundance of grass species and dicotyledonous forbs, while a woody vegetation component occurs as sheltered islands of temperate mountain bushveld within the grassland.
Lesedi Local Municipality (LLM)
Lesedi falls within three vegetation types: (Lesedi EMF, 2006). LLM falls within Moist Clay Highveld Grassland where Themeda triandra dominates in primary grassland; 72% of which is transformed and 0,29% conserved, and Rocky Highveld grassland with shallow rocky soil, which is a transitional type between the high inland plateau grassland and the lower inland plateau bushveld. Of the area covered by this type of grassland, 65% is transformed and 1,38% conserved (Low and Rebelo, 1996). The area is very rich in herbaceous species, both dicotyledons and monocotyledons.
Samples and sampling sites
Water samples were collected from the identified nine (9) sampling sites along the Blesbokspruit based on the activities and potential contributors or impactors on the quality of the river water. The sampling points were denoted as BB from 1-9, where BB was acronym of the name of the river “Blesbokspruit” while number 1-9 represent the nine sampling points along the river corresponding to the flow of water from up- to downstream. The quaternary drainage map and the Quaternary drainage topography map showing sampling points are represented respectively. Two Litre (2L) of surface water samples were collected into clean acid washes plastic containers at about 5 cm below the surface of the water from sampling points. These were kept cool in a cooler box and transported to the laboratory for analyses. Water samples for microbiological investigations were collected in 2L sterile glass bottles and taken immediately to the laboratory for refrigerating. Analyses were carried out within 12h of sample collection according to Clesceri et al., 1998 and RQS 1999.
1. Introduction / background information
1.2 Problem statements
1.3 Rationale / justification for the research
1.4 The aims of the research
2. LITERATURE REVIEW
2.2 Pollution and sources of pollution
2.3 Point and non-point sources of pollution of surface waters
2.4 Water Quality Management
2.5 Types of water users and their associated water quality concerns
2.6 Factors impacting on water quality not classified as water users
2.7 Impact control
3. RESEARCH DESIGN AND METHODOLOGIES
3.1 Brief Introduction
3.2 Study area
3.3 Description and overview of the catchment
3.4 Samples and sampling sites
3.5 Water sampling protocol
3.6 Materials and Methods
4.1 Results of parameters analysed in collected samples per sampling period
4.2 The mean results of analysed parameters per sampling point
4.3 Overall mean values and graphical presentations of analysed parameters in water samples
4.4 The seasonal variation of analysed parameters per sampling point
4.5 Statistical evaluation/treatment of the results of analysed water Samples
5. DICUSSION OF RESULTS
5.1 Discussion of Results
5.2 Assessment of results against the Instream Water Quality Objectives for the Blesbokspruit
5.3 Assessment of results against South African Water Quality Guidelines
5.4 Ecological status of the Blesbokspruit
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