Protecting limited water resources under increasing climatic stress and landuse intensification is a significant challenge. With limited funds, managers must ensure they attain maximum water quality return for the funds invested.  This paper describes an approach for targeting rehabilitation works by indentifying the influences of vegetation, landuse, and geology at both catchment and riparian scales.  Although vegetated riparian zones should reduce water quality degradation through buffering non-point source pollutants, catchment factors, such as wide-spread deleterious land uses, may limit the impacts of vegetated riparian zones on water quality.  This paper presents whether riparian vegetation, land use, or geology has a greater impact on water quality in ephemeral streams in South East Queensland, Australia.  Riparian vegetation, land use, and geology are analyzed with Geographic Information Systems and water quality data is from event monitoring stations in three focal catchments.  Through comparing catchment and riparian scale variables, this research will contribute significantly to our understanding of the key factors that degrade water quality in South East Queensland while outlining an effective first step for spatially optimizing water quality management interventions.