Statistical Considerations in the Development of Environmental Indices: The Example of the Canadian Water Quality Index
Sylvia R. Esterby1, Abdel H. El-Shaarawi2
1Mathematics, Statistics and Physics, University of British Columbia Okanagan, Kelowna, BC, Canada; 2National Water Research Institute, and McMaster University, Burlington, ON, Canada

It is now widely accepted that human health and well-being are highly dependent on the quality of the environment, yet the health of the environment plays a much less prominent role in public policy than do economic considerations. The development of environmental indicators and aggregated indices is seen as a way to facilitate the integration of environmental information with social and economic information. Indicators constructed for public policy purposes are expected to provide information in a form readily understood by decision makers and the public. An indicator should also be quantitative and based upon an underlying model which relates the indicator to the more complex phenomenon being summarized. The Canadian Water Quality Index (WQI) provides an example of the development of an index where 1) it was recognized that simpler summaries were needed for the public and decision makers, 2) monitoring data were already being collected, and 3) the scientific understanding of water quality was used to guide the development of the index. During the development of an index and subsequent evaluation, statistical thinking and methodology can contribute in various ways. Since the WQI is an aggregated index, investigation of the value of the index, generated by various scenarios of underlying water quality variable values, needed to be assessed to ensure that low or high water quality according to the index agrees with what a more multivariate assessment would have given. A measure of variability of the index is also necessary. A number of issues, including these two, will be considered for the WQI using data from several Canadian provinces. The role and form of the WQI in the context of a suite of sustainability indicators will also be considered.

Keywords: Water quality index; Sustainability; Statistical considerations; Public policy

Biography: Dr. Esterby teaches statistics at the University of British Columbia Okanagan and has worked on water quality problems for a number of years