Environmental Engineering Reference
In-Depth Information
provision of penalties with respect to clear cases of identified polluters would be difficult
to implement.
Considering the random character of natural water quality, it should be well
understood that 100% compliance is not possible. The choice of confidence level would
determine the level of the stringency of the prescribed criteria. More relaxed standards
could have lower cumulative probability requirements, which means that the cases of
non-compliance along the period of observation would happen more often. In cases when
toxic or other human health related criteria are exceeded, an important factor, which
should be considered and specified in regulatory instruments, would be the duration of
the exposure of the aquatic environment to the respective contaminant. In other words,
when the standard prescribes a specific allowance for exposure to higher concentrations
than the prescribed limit, it should also specify the period of allowable exposures.
In general, the frequency of the prescribed monitoring observations would vary for the
different locations and type of media observed. Ground water quality does not vary
rapidly, thus a lower frequency would be recommended. With respect to surface water
bodies, a clear differentiation in the monitoring methodology should be done between
rivers and lakes (dams). In general, larger rivers have a much more stable water quality
compared to small streams. In cases where a naturally high variability of the data sets is
expected, regulatory documents could provide for an acceptable range of variation of
specific parameters, rather than fixed values.
3.3
Water quality regulation and models applications
The application of the water quality objective approach, together with the integrated
assessment of the catchment characteristics and the formulation of specific criteria with
respect to beneficial water uses, leads to an extremely large volume of information to be
considered during the preparation and implementation of regulatory instruments. The task
to analyze and evaluate such information could be regarded as unattainable without the
application of contemporary tools for information storage, retrieval and analysis, as well
as modeling of different processes and simulation of different scenarios.
Considering the nature of diffuse pollution and urban drainage specifically, pollution
loads' magnitude would be determined by the land use and rainfall patterns. Therefore,
its correct estimation would depend heavily on the proper evaluation of the characteristics
of the drained area, the use of reliable methods for runoff estimation, and reliable rainfall
data sets. These factors, presented in the form of an information database, together with
the information provided by the corresponding water quality monitoring programs, result
in a massive information block, which is difficult to be handled and interpreted manually.
For this reason, the estimation and control of diffuse pollution requires the development
and implementation of models, based on GIS systems, which could provide the necessary
means for data handling, storage and retrieval. Also, the application of such tools would
improve the reliability of results obtained and their level of accuracy. Their application is
even more relevant for the cases of urban drainage pollution, where the variability of land
use practices per unit area is much higher, compared to cases of agricultural diffuse
pollution. However, most countries in the region do not have the capacity to develop and
maintain such tools at present. It means that the practical implementation of the water
quality objective approach in the region should be viewed as a long-term task, which
