Evaluating the suitability of water quality indices for the health of urban waterways : a case study of the Parramatta River

An appropriate water quality index is important for developing strategies for public health and wellbeing in a given urban area. This study set out to compare the National Sanitation Foundation Water Quality Index (NWQI) and Canadian Council of Ministers for the Environment Water Quality Index (CWQI) in terms of accuracy and overall utility, in the context of a parameter limited water quality monitoring and management. To do this, water quality data were collected from the Upper Parramatta River, Sydney, Australia, a waterway draining a highly urbanised catchment. The parameters included in this study were dissolved oxygen, pH, electrical conductivity, total dissolved solids, turbidity, phosphates (as filterable reactive phosphates) and nitrates. Biological parameters were also tested, with macro-invertebrate surveys and bacteriological tests for faecal coliforms, total coliforms, Escherichia Coli (E. coli) and enterococci. Additionally, corridor imperviousness of tributaries was determined using GRASS-GIS and compared to index results. The results of this study showed that the NWQI did not act as an accurate representative of water quality, but did generally behave in line with current models of urban stream syndrome. The CWQI was found to be more accurate in terms of range but the modified CWQI based on some changes in the CWQI parameters was found to be more accurate. While this study cannot endorse the use of any index studied as a tool for meaningful water quality analysis, it does suggest that a modified CWQI be considered as a tool for the preliminary assessment of water quality and for community education in urban areas.