Environmental Engineering Reference
In-Depth Information
introduced to the treated water, as a result of algae blooms and the general decay of
aquatic vegetation, which requires an additional treatment stage in order to obtain a good
quality of the water supplied to the public.
Considering the importance of the Lake water quality, with respect to the water
resources practice in general and the diffuse pollution management in particular, more
extended information regarding the past development and trends of its quality is given in
section 3.
2.3
Urban land use patterns
The city of Harare has a well-developed infrastructure and clearly defined types of urban
development. Figure 3.3 represents graphically the city's urban planning scheme and the
different types of land use practice. The urban planning provides a considerable
percentage of developed, as well as natural open spaces and grounds, which could serve
the purpose of environmental buffer zones for diffuse pollution reduction and alleviation.
The city center comprises of high stories office buildings, used for institutional,
governmental, commercial and business activities. The Central Business District (CBD)
has a high level of impermeable cover and generates a considerable amount of runoff.
To the north of the CBD, residential areas are located, comprising of three-four stories
blocks of flats, which gradually convert into single housing plots. The vast majority of
the residential areas in the City comprise single story housing.
An approximate differentiation between the different types of residential areas, based
on the average size of the plots could be done. Low-density areas comprise of housing
plots with areas higher than 3000 m
2
, medium-density plots vary in size from 800 m
2
to
3000 m
2
and high-density urban developments consist of plots between 300 m
2
and 800
m
2
.
Low, medium and part of the high-density residential areas have well-developed
infrastructure in terms of roads, electricity and water supply, sewerage and drainage
structures, as well as solid waste management. Low-density areas use on-site sanitation
systems, while medium and high-density areas are provided with gravity sewers. Housing
developments in low and medium-density areas include well-developed and maintained
gardens and green areas, which absorb runoff. Also, within residential areas, provision
has been made for shopping centers, which contain commercial and business enterprises,
as well as educational facilities, mainly primary and secondary schools. A considerable
part of the high-density areas have basic infrastructure in terms of roads, water supply
and sewerage, which in numerous cases, has not been maintained properly.
Industrial areas are located in the southern and south-east part of the city. It is a mixed
land-use pattern, with predominantly light industry, food processing, cosmetics,
automotive services and different types of commercial enterprises.
During the last decade, the city has expanded mainly with respect to its residential
areas by new developments in the three different categories. However, the high rate of the
population growth, as discussed earlier, has an adverse effect on the urban development,
because the new-coming population in its vast majority consists of low income or
unemployed population, who move from rural areas to the capital city in search of jobs
and better life conditions. This has resulted in the emergence of high-density housing
areas and small-scale industries, developed to the south-west of the city, to the north and
