Environmental Engineering Reference
In-Depth Information
Population growth and distribution have significant roles to play in the sustainability
of the world's vast resources. The population growth, together with the social and
consumption patterns, as well as the economic conditions, all have a direct effect on the
environment. When we look at the impact of human activities, the situation is more
complicated due to the diversity in the consumption patterns worldwide. A direct link
between population growth and the status of the environment is difficult to be
established. However, the view that population growth is solely responsible for all
environmental ills, is highly objectionable. Population growth is only one of the several
factors that place pressure on the environment in general and water resources in
particular. Land distribution, inappropriate government policies, ineffective management
practice, and inappropriate technologies, all of these and others could be mentioned as
contributors to the environmental decline in over-populated areas. Thus, the population
growth is one factor among many that exacerbates or multiplies the negative effects of
other social, economic and political factors.
2.2
The catchment area
The city of Harare is located in the Manyame River catchment (Fig. 3.2), which
comprises of different types of land use practice. It contains the highly urbanized areas of
the capital city and the satellite town of Chitungwiza, as well as smaller population
centers of urban type. Agricultural lands comprise of crops-growing fields and open-
space animal farms. The total catchment area is 3930 km
2
and the sub-basin of lake
Chivero and tributories, which recieves the runoff and the effluents of the city of Harare
is 2250 km
2
.
In terms of agricultural practice, a differentiation could be made between small-scale
agricultural activities in the so-called “communal farms” and large-scale activities in
“commercial” farms. Rural settlements are located in the upper reaches of the basin and
consist of villages with a traditional African lifestyle. Natural pristine areas, as well as
protected natural reserves, provide the habitat for diverse wild life and are relatively
unharmed by human activities. Figure 3.2 presents a map of the Manyame River
catchment basin and tributaries with water and wastewater treatment plants.
The city of Harare is located in the sub-catchments of the Mukuvisi and Marimba
Rivers, the satellite town of Chitungwiza drains into the downstream reaches of Nyatsime
River, while the suburban town of Ruwa drains into Ruwa River. Lake Chivero (formerly
known as Lake McIlwaine) and Lake Manyame are man-made reservoirs, constructed
with the main purpose of water supply for the capital city. Due to its downstream
location, Lake Chivero is the natural sink of the surface run-off and effluents from the
above-mentioned areas. Its major beneficial use is to supply a major part of the potable
water demand for the City of Harare, but it is also a well-established recreational center
and the natural environment for a wide variety of wildlife. This complex pattern requires
an integrated approach to the water resources management practice, where water quality
control and pollution abatement measures should be given priority. Decisions regarding
the provision of safe potable water for the city of Harare, the proper management of
effluents generated, and the protection of the environment should be made on the basis of
sound
