Use of decision support systems to improve dam planning and dam ...

4. DSSs in the planning and operation of
large dams
Key message
Both the nature of decisions and those making the decisions change at different stages in the planning cycle
of a large dam. The information required at each stage varies but, throughout, the ecological and social
implications should be given as much consideration as the engineering and economic aspects. DSSs can assist
decision making at all stages of the project cycle.
4.1 DSSs and decision making
As human population increases and societies develop, water resources are increasingly under pressure with
the result that the management of water has become an increasingly complex endeavor. Decision making
is complicated not only by the natural variability of hydrological systems but also by the multiple, often
conflicting, demands placed on water resources. DSSs are information systems that support decision makers
to formulate alternatives and select options. A properly designed DSS will help decision makers by providing
information in an understandable form at the appropriate time. The information provided by a DSS should
assist decision makers to better understand their system, its problems and alternative ways to address them
(Loucks and van Beek 2005).
The contribution made by DSSs to decision making processes varies considerably. A hierarchy of six broad
approaches can be envisaged (Figure 4.1). In a completely unsupported process the decision maker makes
the decision based solely on his/her knowledge and intuition. In a completely automated system a DSS will
actually make the decision with no human input at the time the decision is made. For example, the emergency
operation of spillway gates during a flood event may be predetermined and triggered simply when reservoir
water levels reach a certain height. Although such systems are rare, they do exist. Between these two extremes
the role of the DSSs can differ with relatively greater or smaller inputs to the decision making process.
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Data provided
by
Data
analyzed
by
Options
generated
by
Decision
selection by
Decision
implemented
by
Approach to decision
making
1 Decision maker Completely unsupported
2 Database/GIS Decision maker Information Supported
3 Database/GIS DSSs Decision maker
4 Database/GIS DSSs Decision maker
Systematic analysis
Systematic analysis of
alternatives
5 Database/GIS DSSs Decision maker System with override
6 Database/GIS DSSs Completely automated
Figure 4.1. Variable contribution of DSSs to decision making (adapted from O’Callaghan 1996).