Urban Growth in Metropolitan Cape Town: Implications for Inland and Coastal Waters
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URBAN GROWTH IN METROPOLITAN CAPE TOWN: IMPLICATIONS FOR INLAND AND COASTAL WATERS Arthur Joseph Rex Quick Rapid and poorly planned urban drainage catchments revealed that potentially negative impact of in growth in Metropolitan Cape Town is most will occur in the False Bay north creased potable water demand on the subjecting the inland coastal waters in shore catchment. Priority planning Berg, Riviersonde rend, Breede and the region to stress. Increasing ex concerns identified are: (1) the lack of Palmiet riverine ecosystems; and (5) tractive demands are being made on fundamental scientific information on the opportunity cost (e.g. water un inland water systems to provide pot coastal ecosystems, particularly those available for agriculture) of increased able water. Larger volumes o f liquid o f False Bay and Table Bay; (2) the abstraction of river and groundwater and solid waste, and increased storm- potentially detrimental fhealth) impact for urban consumption. The paper con water runoff are impacting negatively o f bacteria and viruses in urban runoff cludes by emphasising the need for a on inland and coastal water quality. and from treated wastewater discharge metropolitan inland and coastal waters Urban sprawl is detracting from the on inland water and coastal recreation management policy to address the lack aesthetics o f river catchments, and is nodes; (3) the potentially detrimental of coordinated policy and planning also impacting adversely on river and impact o f nutrients in urban runoff and within and between local authorities stormwater quality. An assessment of treated wastewater discharge on in and government departments. future urbanisation in terms o f major land and coastal ecosystems; (4) the INTRODUCTION the urban area is detracting from the rised in Figure 1. There are three aesthetics of river catchments and also discrete drainage systems, the False Rapid urban growth is occurring in causing a deterioration in the quality Bay catchment, the Table Bay and Metropolitan Cape Town, with the of stormwater runoff (Quick, in press). Atlantic Ocean catchment and in the population growth rate during the past east of the metropolitan area, the decade averaging 4,5 per cent (Repub These developmental issues have catchments of the Berg, Bree (Rivier- lic of South Africa, 1985; 1991). The serious implications for planning and sonderend and Breede Rivers) and present population, which is approach management in Cape Town, particular Palmiet. ing 3 million people is growing at a ly in view of the fact that the future rate of 2,5 per cent and is predicted to economic growth of the region is de False Bay and its catchment, have increase to 3,5 million by the year pendent on tourism, high technology been described in detail by Jackson 2000 (Spies and Barridge, 1991). An manufacturing, insurance and finance (1991) and Quick (in press). The estimated 30 per cent of the economi (Bridgeman et al., 1992). All of these catchment is drained by eleven rivers cally active population are currently require high standards of environment and includes two coastal lakes (Zee- unemployed, and 60 per cent of quality. koevlei and Zandvlei) and the Steen- blacks, 40 per cent of coloureds and bras Dam which supplies 10 per cent Although (Gasson, 1989a and b; 1990) 19 per cent of whites are living below of Metropolitan Cape Town's water has described the urban demands being the minimum household subsistence (Department of Water Affairs and made on the natural systems of Metro level of R600 per month (Dewar et al., Forestry, 1992). The largest river politan Cape Town, no detailed infor 1990; Bridgeman et al., 1992). Prob system is the Eerste/Kuils River which mation is available on implications of lems of poverty and unemployment are drains a catchment of 710 km2. The urban growth for inland and coastal exacerbated by an acute housing short Sand, Zeekoe and Lourens Rivers waters. This paper, therefore, aims to: age, which is in the order of 100 000 dominate the remainder of the catch (1) describe the characteristics of the units (information from Town Planning ment and drain subcatchments of 93,83 major water bodies, rivers and catch Branch, Cape Town City Council). and 140 km2, respectively. The Cape ments; (2) evaluate the effects of Flats aquifer is situated on the central Increased potable water demand has present urbanisation cm water quality northern shore of False Bay. The resulted in the construction of dams and water demand; (3) identify areas aquifer is estimated to have a safe and greater abstraction of water from of potential future urban growth and yield of 15 - 20 x 106m3y~‘ (Gerber, rivers, particularly along the eastern implications for water quality and 1981; Vandoolaeghe, 1990; Ninham margin of Metropolitan Cape Town water demand; and (4) identify the Shand, 1992a). (Spies and Barridge, 1991; Department inland and coastal waters planning and of Water Affairs and Forestry, 1992; management priorities in Metropolitan The available information on Table in prep. a). Liquid and solid urban Cape Town. Bay has been reviewed by Quick and wastes are impacting negatively on the Roberts (1993). Two major river INLAND AND COASTAL WATER False Bay and Table Bay catchments systems drain into Table Bay, the Diep SYSTEMS (Quick and Roberts, 1993; Quick, in and the Salt/Black Rivers. A coastal press). Sprawl, including informal The inland and coastal waters of lake, Rietvlei, and a wedand area are housing settlements, along the edges of Metropolitan Cape Town are summa situated immediately to the north of l Town and Regional Planning No. 35, 1993 Town Town and Regional Planning No. 35, 1993 Figure 1. The inland and coastal waters of Metropolitan Cape Town. Figure 2. Place names and jurisdictional boundaries in Metropolitan Cape Town. the Diep River mouth. The Newlands Table 1: Population by Catchment aquifer (about which little is known) is situated in the Salt/Black River catch Catchment Population ment To the north of Rietvlei are the Salt River catchment and the Atlantis aquifer. The Atlantis aquifer is artifi Atlantic Ocean cially recharged using stormwater and is the potable water resource for South of Table Bay #1 73 152 Atlantis, supplying approximately 5,1 Table Bay Harbour *2 4 2 892 x 106m3y 1 (Ninham Shand, 1992a). Salt/^lack River 8 9 7 9 32 Two small river systems are situated to Diep River 98 645 the south of Table Bay, the Hout Bay North of Table Bay *3 80 118 River (which drains into Hout Bay) Total 1 192 793 and the Noordhoek Wetland system. Eastern Catchment The Berg, Riviersonderend and Pal- Berg River 4,4 119 107 miet catchments supply most of Total 119 107 Metropolitan Cape Town's water. According to the Department of Water False Bay Affairs and Forestry (1992), dams on Peninsula *5 21 36 4 the Berg River system supply 35 per Northwest shore *6 555 222 cent (126,4 x 108 m3 y 1) of Cape Northcentral shore * 7 8 86 6 24 Town's water allocation, whilst the Northeast shore *8 145 04 7 Riviersonderend catchment supplies Total 1 6 0 8 2 5 7 approximately 51 per cent (186 x ltfW y 1). Grand Total 2 9 2 0 157 URBANISATION The jurisdictional boundaries of * 1 Groan Point to Scarborough * 2 Central business area and surrounding suburbs metropolitan Cape Town are shown in * 3 Bloubergstrand. Melkbosstrand. Atlantis. Philadelphia and Mamre * 4 Paarl/Mbekweni, Wellington. f-ranschoek/Groendal. Kylemore and Pniel Figure 2, and the extent of urbanisa * 5 Kalk Bay to Simonstown * 6 Sand and Zeekoe River catchments and stormwater catchments of Muizernberg. Pelican Park and Strandfontein tion in Figure 3. A breakdown of the * 7 Kuils River catchment and stormwater catchments of Weltevreden Valley. Mitchells Plain and Khayelitsha * 8 Sir Lowry's Pass. Lourens and Eerste (excluding Kuils River) River catchments and stormwater catchments of Strand and population by catchment is given in Gordons 8ay Table 1. Most urbanisation has taken Sources: Cape Town City Council (Town Planning Branch. Surveys and Land Information Branch), and Western Cape Regional Services place in the Salt/Black Sand, Zeekoe Council and Republic of South Africa (1985. 1991). Spies and Barridge, 1991). The present False Bay are shown in Figure 5. and Kuils River catchments. The potable water resources being utilised Potential point sources of pollution in remaining area is dominated by to satisfy urban requirements are the catchment include 12 wastewater agriculture and mountains. It should be summarised in Table 2 and Figure 4. treatment works and 13 sanitary land noted that 95 per cent of the informal fill sites (Figure 5; Table 3). Areas of housing population is in the False Bay Urbanisation and environmental the coast where numerous small storm catchment, concentrated mainly in the water quality water outfalls discharge are also shown townships of Nyanga, Crossroads False Bay catchment as they are of concern with respect to (including KTC), Guguletu and Khaye water quality. litsha. Rivers, major stormwater outfalls, wastewater treatment works and indus The management of water quality in Virtually the entire metropolitan coast trial outfalls discharging directly into False Bay and its catchment has been line is utilized for recreation. Nodes where intensive water-contact recre Table 2: Present water resources for urban usage (Department of Water ation occurs are shown in Figure 3. Affairs and Forestry, 1992) There are only four inland water bodies which are used for water-con tact recreation, these are Zandvlei, Resource Yield (x 108m3y ') Zeekoevlei, Milnerton Lagoon and Rietvlei. Table Mountain dams and fountains 5.1 Steenbras Dam 36.0 Urbanisation and potable water Wemmershoek Dam 56.4 The water demand for Metropolitan Allocations from Voelvlei Dam 70.0 Cape Town during 1991 was estimated Paarl and Wellington (Municipal dams and Berg River) 2.0 to be 260 million m3y'‘ (Water Re Stellenbosch (Municipal dams) 5.7 search Commission, in prep.).