A global service quality index to evaluate the performance and sustainability in water supply utilities

Abstract

Water supply systems are a structural part of public utilities and as such are vital to the general wellbeing, public health, safe drinking water use, economic activities and environment protection. The principal objective of regulation is to protect the interests of users by fostering quality in the services provided by utilities and ensuring a fair balance in the charges levied, guaranteeing the essentiality, equity, indispensability, feasibility and cost-effectiveness principles. The use of performance indicators is widely recommended as a measure of the utility’s effectiveness and efficiency. In Portugal, the regulation of service quality is conducted by ERSAR (Portuguese Authority for the Regulation of Water and Waste), which has decided to define its own set of performance indicators that is less comprehensive than those adopted by the IWA (International Water Association). Currently, the adopted system does not provide a quantitative and integrated evaluation leading to an overall ranking of utilities’ performance and sustainability. The aim of this paper is to contribute for the improvement of the Portuguese performance assessment system, through the development and application of a complementary methodology to define a global index of service quality (GISEQ) for a given water supplier in order to achieve accurate performance rates. This methodology allows a truly quantitative evaluation in which each performance indicator represents a criterion to be considered and judiciously weighted, based on the results of an on-line questionnaire proposed to a selected set of academic and professional experts. The GISEQ values are calculated as a weighted linear combination of the normalised scores of each performance indicator, which is one of the most common aggregation procedures available in the context of multicriteria evaluation. The criteria normalisation process essentially based on fuzzy sets defined for each indicator, considering the established ERSAR or legislation standards. An innovative approach to weights definition was also performed as well as a sensitivity analysis of GISEQ values to different weighting methods.