Environmental Engineering Reference
In-Depth Information
Source: Ministry of Natural Resources and Energy, Swaziland (Msibi 2001)
and rainfall vary markedly with season, as well as with altitude. In winter (May to
August), rainfall is scarce and temperatures are low. The minimum temperature in the
High veld could reach 4ºC, although the average annual temperature is 10ºC. The annual
average temperature in the Low veld during the summer (November to February) is 29ºC.
3.2
The study area
The Mbabane River originates at the eastern foot of the Nkoyoyo hills a few kilometres
west of the city. It flows throughout the city (Fig. 11.7), collecting surface run off from
residential areas such as Nkoyoyo, Sidwashini, Selection Park, Sandla, Manzana,
Extension 3, and Mobeni flats. Other types of land use patterns include the commercial
areas in the city centre and different type of small industries such as: Chemlog and
Superchem (manufacturer of industrial and domestic cleaning, floor care material,
chemical solutions etc); Rand Continental Tool (manufactures of paints); automotive
service and filling stations; abattoir; and different types of food processing industries.
The river passes beside the very busy Mbabane bus terminus where people throw
waste, fruit peels and bottles into the river, and along the Mbabane Market where traders
wash their fruits and vegetables. After the market place and further downstream, the river
flows through the industrial estate, where the main industrial activities are mechanical
workshops, service stations and garages. Spilled used oil, grease and other chemicals
from these small enterprises find their way into the river. From the eastern flank, there is
Pholinjane stream - a tributary of the Mbabane River, which collects surface run-off from
the Sidvwashini industrial estate. The river then flows south and links with Mvutjini
River at the foot of Malagwane hill.
Gobholo treatment plant discharges into a small nearby stream, which joins Mbabane
River a few kilometres downstream the discharge point. This study concentrates on about
30 km stretch from where the river originates (Nkoyoyo Hills) upto the Mvutjini area
downstream of the city.
In the upper reaches of the Mbabane River, the sources of pollution are run-off from
pastures and a few small areas of vegetable growing. The additional run-off from the
areas of indigenous vegetation also enters the river. From general observation, the water
quality upstream appears to be good.
In the vicinity of the city, there is a change of colour in the river. This is noticeable
just after the river flows past the industrial and residential areas. In one of the residential
areas (Sidvwashini), there is evidence of landslide, which eventually enters the river
during rainy days. In general, the riverbanks and riverbed have been used for the disposal
of solid wastes and garbage, which is visible at many locations and near the city centre.
Further downstream, after the industrial site, there is evidence of foam, possibly from the
chemical industries and also a film of oil and grease on the river from the mechanical
workshops, service stations and automotive garages. Organic pollution from the abattoir
could be an additional pollution source, which finds its way into the river. In addition, the
sewage effluent from the Gobholo treatment plant also reaches the Mbabane River
(Fig.11.7)
