Development of regional freshwater water quality and catchment guidelines for the conservation of aquatic ecosystems : a case study from the Georges River catchment

The conservation of freshwater ecosystems in Australia is commonly underpinned by comparing water quality data with the ANZECC water quality guideline values. In this study we formulate and recommend regional aquatic ecosystem guidelines for the Georges River catchment. We use a rapid assessment approach, undertaken by non-specialist personnel, based on the collection of freshwater macroinvertebrates, to directly measure the ecosystem health of freshwater reaches within the waterways of the Georges River catchment, in south eastern Australia. The 18-month study involved spring and autumn assessment of water quality (chemical and physical), benthic macroinvertebrates, riparian vegetation and calculation of catchment imperviousness. The results showed three distinct disturbance groups emerged which were categorized as 'low', 'moderate' and 'high' effective impervious. We set out to develop a methodology that can be easily and practically applied by natural resource managers and consultants, rather than a methodology typically employed by specialist scientists. The study revealed that urbanised streams with high effective imperviousness had strongly degraded water quality and macroinvertebrate communities, compared to clean non-urban reference streams. Based on the results of this study, we recommend interim regional ecosystem and water quality guidelines for the assessment and conservation of the remaining clean freshwater streams in the Georges River catchment.