National Outfall Database Ranking Report 2018-2019 Financial Year

This report provides an analysis of the Australian coastal outfalls and ranks them according to the total flow volume and nutrients load to prioritize the potential degree of impact of each source to the environment and human health. The pollutant contribution index, based on nitrogen and phosphorous loads, was calculated for each outfall. Outfalls were ordered from lowest to highest index value to rank them according to their relative pollutant contribution to the coastal and marine environment. The index is based on a total nutrient load discharge using the variables of flow, nitrogen and phosphorous. The ranked loads throughout Australia were mapped by quartiles. The top quartile (lowest nutrient load) of outfalls seem to be more prevalent in regional areas and discharge less nitrogen and phosphorus loads into the coastal and marine environment. The bottom quartile, on the other hand, with higher nutrient loads principally occur around the major cities. This ranking of nutrient loads from Australian outfalls by site at a national scale can therefore be useful in prioritizing treatment upgrade resources to manage biodiversity impacts and human health concerns.

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