Environmental Engineering Reference
In-Depth Information
case of tropical countries with distinctive wet and dry seasons, the major pollution loads
are expected during the beginning of the rain season; therefore, the frequency of sampling
during this period should be higher. The intensity of rainfall events is also an important
factor because of its erosive effect and the increased risk of the transport of pollutants and
should be included in the data sets. A proper determination of the annual frequency of
sampling should be done, based on a detailed examination of the rainfall patterns specific
for the region and should provide enough data for statistically reliable results.
Storm water quality monitoring in urban areas, specifically in cases of large drainage
channels, could be regarded as a point source of pollution and should be subject to a
separate monitoring program. The regular monthly monitoring of urban drainage, as in
the case of the city of Harare (Chapter 3), would not provide adequate information. The
determination of EMCs and unit pollution loads from typical land use patterns, or typical
unit pollution loads for selected areas, drained by one drainage channel, could drastically
reduce the cost of regular monitoring programs and could be very useful for the analysis
of impacts and future developments. This could be done by means of separate projects
and the application of automatic monitoring stations, as the procedure requires a high
frequency of observations. The data obtained during such projects would be used for
pollution loads estimation and the evaluation of different scenarios of future urban
development. If the data with respect to EMCs is available, then the regular monitoring
programs could have a lower frequency and the data obtained from them could serve as
back up information and data validation. Also, it should be noted, that the design of a
monitoring program is not a “once for ever” exercise but should be viewed as a process.
The regular periodical assessments of its effectiveness and the consequent improvements
are mandatory.
The data quality assurance aspect should be mentioned as pivotal for the success in the
implementation of any monitoring program. It is directly connected to the available
financial, technical and human resources potential and if these resources were not
provided, the basic objectives of the monitoring program would be jeopardized. The
proper data validation and storage procedures should be executed on a regular basis to
minimize errors occurrence. The quality assurance measures are even more important in
the cases of diffuse pollution control, because they would allow eliminating gross
measurement errors and would reduce the natural high variability of the data sets, due to
the uncertainty of rainfall occasions and runoff quality.
Designing a monitoring program requires expert knowledge, a good understanding of
local conditions and consideration of the operational costs involved. It could be
recommended that it is better to reduce the number of monitoring sites, but to have a full
set of all necessary data with respect to this site, than to expand to numerous locations,
with scattered monitoring data. For locations in remote areas, or low cost urban
developments, the incorporation of biomonitoring techniques and their integration in the
monitoring process could be a viable option, which could help to considerably reduce the
monitoring cost and to involve the community in the process.
2.4
Biomonitoring
Aquatic ecosystems are sensitive to changes in their environment, due to natural or
anthropologic causes. The response to such changes might be drastic, resulting in the
