NSF-Water Quality Index: Does It Represent the Experts’ Opinion?

Abstract

Over the last four decades, a number of environmental indices including water quality indices and air pollution indices have been formulated and used. Usually, the indices are formulated based either on studies conducted by the indices’ developers, or are formulated based on the Delphi technique, which takes into account the opinion of experts. In 1970, Brown et al. used the Delphi technique to formulate a water quality index (WQI) for the National Sanitation Foundation (NSF) of the United States. However, it has been observed that the procedure followed for the formulation of the index does not accurately represent the opinion of the experts who responded to questionnaires. In this technical note, the shortcomings in the formulation of the NSF-WQI are brought out and possible improvements in the development of this index are presented.