Environmental Engineering Reference
In-Depth Information
reliability of water required for beneficial use, together with the ecological function of
water bodies must be recognized and attained. Moreover, after the introduction of the
“White paper” in 2000, the integrated water resources management policy was clearly
stated. The policy, among other things, aims towards the regulation of pollution and a
proper management of the receiving environment. However, at the level of practical
application, most of the regulations are in the process of development.
Zimbabwean pollution control regulations are discharge orientated. The latest
revisions consider pollution from runoff and suggest that both the owner and the user of
an artificial storm drain require a permit for discharge into any surface water body
“whether directly or through drainage” (WWEDR 2000). This implies that the main
responsibility for the reduction of diffuse pollution lies with the local urban authority and
at the same time does not make provision to identify pollution of diffuse origin, as in the
case of low-income urban areas, or agricultural pollution, where no specific discharge
point could be identified.
The application of the water quality objective approach in the regulatory practice
would rely heavily on the site conditions, and the specific geographic, climatic, economic
and social factors. For example, in many African countries, the vast majority of the
smaller rivers and streams are ephemeral and during the dry season, the flow, which
could be found in them, is due to point effluent discharges. Under such circumstances,
they could be treated as natural channels for the conveyance of effluent at a different
level of treatment. It is clear, that in such cases, we cannot rely on the natural assimilative
capacity of the body, and that an effluent orientated approach would be feasible. In cases
of larger surface water bodies, a water quality orientated approach for protection and
pollution prevention, together with assessments of their assimilative capacity would be
feasible. Regulatory documents with respect to ground water resources should account
for the fact that their assimilative capacity is very limited and should be orientated
towards minimum or zero pollution loads.
Many of the small-scale ephemeral streams and rivers, which are located downstream
of urban population centers or industrial enterprises, are used by rural population for
bathing, drinking and washing activities, directly and without any pretreatment. This
scenario could be met very often in many African countries and examples are given in
Chapters 8 and 11. In such cases, the effluent discharge water requirement should meet
the WHO criteria. This requirement makes the effluent treatment cost very high and
could influence the development of the whole region. In such conditions a balanced
solution with respect to regulatory instruments, involving compromises from all
interested parties, together with a wide public and all stakeholders' involvement is
mandatory.
2.3
River water quality monitoring and data collection
Monitoring data regarding runoff water quality from high-density housing developments
is very limited in the region. Considering the low economic status of such types of areas,
and the lack of large runoff collection channels, makes such a monitoring exercise
unfeasible and costly. However, the potential for diffuse pollution from such areas is
high. Therefore, monitoring programs should be orientated towards the examination of
the streams and rivers, which collect the runoff from such areas and compare the results
