Relationship between economic development and pollutant discharge in Southeast Queensland

Some relationships between economic development and pollutant discharge have been found to be represented by inverted U-shaped curves, namely the environmental Kuznets curve (EKC), while S-shaped and N-shaped curves have also been found. There are several hard and soft measures to improve water quality in the rivers in Southeast Queensland. Socio-economic conditions related to river water environment in Australia and Japan have similarities and differences. Comparative investigations have not been conducted so far. In this research, first, qualitative comparisons of the measures to improve the river water environment in Australia and Japan were conducted. Second, the relationships between economic development level and pollutant discharges in Southeast Queensland from 1960 to 2012 were investigated. Pollutant discharges from diffuse sources were estimated based on the existing research results. Effects of precipitation variations were included by introducing the precipitation variation coefficient (PVC) for the diffuse source pollutants. Pollutant discharges from point sources were estimated based on the National Pollutant Inventory (NPI) and the Queensland Government data. The relationship between purchase power parity based gross domestic product (PPPGDP) per capita and pollutant discharges per capita (PDC) of TN and TP were found to show inverted U-shaped curves especially when the precipitation effects were not included. Higher economic development levels of the inflection points than those of the existing research results suggested that the inflection points in the Brisbane River Catchment found in this research should correspond to the pollutant discharge reductions from point sources in the 2000s. The exceptional inverted U-shaped EKC of PDCs in the Yamato-gawa River Catchment, Japan, on the curvatures of the left and right halves of the curves showed the effectiveness of the hard and soft measures for pollutant discharge reduction.