WATER QUALITY MANAGEMENT IN CONNECTED CATCHMENT- SHALLOW LAKE SYSTEMS - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 43

Mass balances : Mass balances can be established using load estimates from pollution sources in
combination with the water flow or residence time in the water body. The significance of the
different loadings can be evaluated by comparing their magnitude to their contribution to the
resulting concentration of the pollutant in the receiving waters. The significance of the different
loadings for the pollution level of the receiving water body provides the rational basis for
decisions on effective reduction of the pollution level in those waters.
Effect evaluation: Assessment of changes in the identified pollution sources and their resulting
concentration in the receiving waters can be made at various levels, from using simple, empirical
relations to long-term mass balance models. An example of a well known empirical relation is the
Vollenweider method for estimating eutrophication effects in lakes (Vollenweider, 1968, 1975,
1976). Based on experience from measurements in a large number of lakes, the method relates
pollution discharges and static lake characteristics (such as water depth and retention time) to
expected effects on the Secchi depth and algal concentrations. Effect evaluation may also
combine considerations about cost effective pollution reduction at the source, the resulting
pollution concentration in receiving waters and the resulting effects in the ecosystem.
Simple mathematical mass balance models : Application of this tool allows consideration of the
possible changes over time in relation to any reductions proposed in pollution load. Many types
of these biogeochemical models have been developed over the years and some are available in the
public domain.
Advanced ecological model: . If higher level effects of pollution loadings on an ecosystem are to
be determined, more sophisticated ecological models are available. Such models may create the
basis for a refined level of prediction and should be used in cases of receiving waters with high
complexity and importance, provided sufficient resources (financial, human or institutional) exist
or can be allocated.
The above examples serve to illustrate that quantitative assessment of pollution problems can be
performed at various levels of complexity, from hand calculations and statistical analysis to advanced
state-of the-art ecological modelling.
There is a wide range of existing water quality management tools. The range of tools and instruments
should be considered as an input to the overall process of achieving effective water pollution control.
They are considered necessary means to address the identified problems. The manager's task is to
decide which tool(s) will most adequately solve the present water pollution problem and to ensure that
the selected tool(s) are made available and operational within the appropriate institutions. Integration
of tools is considered important in some situations where there is a need for better understanding of
the problem and clear interpretation of existing situation.
(a) Regulations, management procedures and by-laws
(b) Water quality standards
(c) Economic instruments
(d) Monitoring systems
(e) Water quality modelling tools
(f) Environmental impact assessment and cross-sectoral co-ordination
The key actions to address water quality management issues and problems include;
1. Development of appropriate, cost effective and reliable data programmes that can inform sound
judgments on environmental policy, management and regulatory needs. This is most important
when we realize that developing countries are extremely data poor, both in amount and reliability
and that part of the current water crisis is the failure of national data programmes to produce
information that can be used to estimate the contributions and impacts of different categories of