Management of diffuse water quality pollution in the Peel-Harvey coastal drainage system: a strategic approach to implementation of best management practices

[Truncated abstract] The Peel-Harvey Estuarine System is one of the most significant waterbird habitats in Australia. However, despite its ecological significance, a serious decline in the water quality characterises the system, requiring catchment-wide waterway protection and enhancement. Although point sources, such as intensive animal industries and urban development exist in the catchment, the majority of pollution originates from diffuse sources in the wider catchment. This requires that due attention is given to catchment controls and characteristics that define 'diffuse' sources. But targeting all sub-catchment areas equally has been shown to be neither cost-effective, nor likely to significantly reduce pollutant discharge. In this work, the drainage system, a combination of artificial and natural drainage lines, is treated as a stream network and classified into a series of management units, to which water quality threats can be attributed. The establishment of channel characteristics in the Peel- Harvey coastal catchment produced nine channel classes, which highlight how the water quality threat varies at differing catchment scales. The classification process has highlighted the distinct differences between sand-based and clay-based catchments. These differences relate to both the functioning and stability of the channels, but also to the type of pollutants and the way these pollutants are entrained, stored and move through the catchment. In providing the means of overcoming the water quality threats, a range of alternatives methods/guidelines are explored, from which the most effective are selected, guiding the implementation of remediation activities, termed here Best Management Practices (BMPs). The thesis has confirmed that small, first-order streams (source zones) are the most effective locations for managing diffuse pollution. Existing BMPs such as vegetation buffers produce impacts that coincidence with those reported in the literature.