Guidelines for the Use of Multicriteria Decision Analysis in the Implementation of the National Water Act
Report No 1298/104

EXECUTIVE SUMMARY

Overview

This report is the culmination of a number of years research at the University of Cape Town, on the role of multiple criteria decision analysis (MCDA) in water resources planning, particularly in the light of the requirements of the National Water Act, Act No. 36 of 1998.

MCDA is that branch of management science and decision analysis which deals with conflicting objectives in decision making in a structured and systematic manner. MCDA provides a rigorous theoretical foundation for a total decision support process incorporating the following key steps:

• Structuring of decision making goals in terms of explicitly defined hierarchies of criteria;
• Evaluation of alternative courses of action or strategies in terms of the extent to which they satisfy each of the identified criteria;
• Aggregation across criteria to generate a measure of the extent to which each course of action or strategy satisfies the overall goals (of management, of society, etc.) represented by the criteria.

Many different techniques within the broad MCDA field have been developed for the above steps. It is not the intention of this report to provide a comprehensive exposition of all of the field (but see, for example, Belton and Stewart (2002) for such an exposition). On the basis of practical experience in action research (see, for example, the case studies included in this document), we have found two approaches to be particularly useful in the context of water resources planning in South Africa. These two approaches are particular implementations of value measurement and goal programming, which we shall denote by VM-MCDA and GP-MCDA respectively.

The VM-MCDA approach evaluates alternatives in terms of simple scoring functions, initially with respect to each criterion individually, and then in an overall sense incorporating the relative importance of each criterion. VM-MCDA is a simple transparent process and is well suited to use in group workshop sessions and for subsequent analysis and consolidation of the conclusions from such workshops.

The GP-MCDA approach is based on specifying numerical target levels of achievement for each criterion, and in using mathematical programming techniques to search for alternatives which come closest to achieving these target levels. GP-MCDA is well suited to use by analysts in the background to generate potential strategies for closer consideration and evaluation by stakeholders.

Further details on each of the two approaches are given below.

This report is subdivided into two main Parts. Part I provides guidelines for the use of MCDA methods, and is organised to reflect the key stages of the water management cycle. The intention is to provide potential users of the approach with understanding of the underlying assumptions and methodologies, and the potential they offer for facilitating different stages of the management cycle. Part II describes a number of case studies in which these approaches were used.