Use of multi-criteria analysis to identify a preferred dam site

How do you make a robust management decision on a preferred site for a new water supply dam when the three short listed locations each have different advantages, disadvantages, issues and costs? How do you compare apples with oranges? When Greater Wellington Regional Council was faced with this dilemma whilst planning future water supply storage for the four cities of metropolitan Wellington, its consultant, MWH NZ Ltd, suggested using multi-criteria analysis as a tool to assist in making this important decision.

Multi-criteria analysis is an analytical approach to assist decision-making that is increasingly being used in New Zealand. However, carrying out the process in a workshop environment, three times, with different groups of participants and with each group identifying its own relevant attributes, applying their own weighting systems and scoring them to identify a preferred option, is unusual. The robustness of the process was confirmed by each group separately determining the same preferred dam site.

While the process provided a clear and defensible preference for one site, it also demonstrated the reliability of the multi-criteria method of analysis, and in this case, the use of facilitated workshops to undertake the analysis.