2009 Key Messages
In 2008-2009, the catchments of South East Queensland received significant rainfall; the highest rainfall in the last decade. While the freshwater streams showed improvements in biological indicators (macroinvertebrates and fish), reflecting the positive influence of more flows from the high rainfall, there were declines in nutrient processing due to the high nutrient and sediment loads (or diffuse source pollution) entering the waterways. The receiving waters of the estuaries and Moreton Bay took the impact of this diffuse source pollution and showed significant declines in ecosystem health with the over-all health of Moreton Bay declining from B- (in 2008) to D (in 2009).
In the past, significant investments in reducing point source pollution (through upgrades to wastewater treatment plants) have resulted in improvements in the ecosystem health of the estuaries and Moreton Bay, especially western Moreton Bay. However this year, any improvement in the over-all health of Moreton Bay resulting from these investments has been overshadowed by the impacts of major flood events. The results of the 2009 Ecosystem Health Report Card highlight that diffuse source pollution is currently the key challenge for managing the health of South East Queensland’s waterways. Thus we must prepare our catchments for high flow rainfall events.
Greater investment in protection and restoration is required, particularly in the catchment areas that are under development pressures such as expanding urban centres and changing agricultural areas and practices. The Healthy Country project, which is a collaboration between the SEQ Healthy Waterways Partnership, SEQ Catchments, Queensland Government and the SEQ Traditional Owners Alliance, is a proof-of-concept initiative which focuses on ways to reduce non-urban diffuse source pollution entering waterways from catchments. The expansion of this initiative to other areas across South East Queensland is needed. In addition, Water Sensitive Urban Design must be implemented across new and existing urban areas to reduce urban diffuse source pollution entering urban streams.
This year’s Ecosystem Health Report Card also raises the need to understand the resilience of South East Queensland’s waterways and Moreton Bay to the pressures associated with extreme rainfall events. How long will it take the waterways and Moreton Bay to recover? As climate variability increases and high rainfall events may become more common, we face an added challenge to maintaining good ecosystem health for our waterways.
In 2008-2009, the catchments of South East Queensland received the highest annual average rainfall since the start of EHMP (in 1999). This resulted in more flows in the freshwater streams, but the increased rainfall carried extremely high loads of sediments and nutrients (diffuse source pollution) from catchments into the rivers, and then to the estuaries and Moreton Bay.
Freshwater
There was no significant change in the overall health of South East Queensland’s freshwater streams from 2008 to 2009. Slight improvements in the biological health indicators (aquatic macroinvertebrates and fish) associated with increased flows from the high rainfall were offset by a decrease in the nutrient cycling indicator. This decrease in the nutrient cycling indicator reflects the overwhelming amount of diffuse source pollution entering the streams too quickly for the waterways to process.
Freshwater streams in the highly-urbanised catchments of Lower Brisbane, Lower Oxley, and Redland maintained F ratings. The Albert Catchment received an improved grade (B- to A-), indicating excellent water quality. Generally, more native fish species and a lower proportion of alien fish were recorded within South East Queensland’s streams this year.
Estuaries
The 2009 Estuarine Report Card results have revealed an overall decline in the ecosystem health of South East Queensland’s estuaries, with only the Caboolture Estuary improving slightly (F to a D-). Of the remaining 17 estuaries, seven retained the same grade as the 2008 Report Card and 10 decreased in grade, with Cabbage Tree, Oxley, Bremer, Logan and Albert estuaries receiving an F. The major drivers of the decline in ecosystem health were increased turbidity, nutrients and phytoplankton abundance, and decreases in dissolved oxygen.
Moreton Bay
The ecosystem health of Moreton Bay was also affected by the high rainfall carrying significant loads of nutrients and sediment from the catchments. This resulted in decreases in water clarity and increases in phytoplankton abundance, total nitrogen and sewage-derived nitrogen and led to a significant decrease in the over-all grade for Moreton Bay (B- to D). Only two of the nine reporting regions improved in grade: Pumicestone Passage (C to C+) and Eastern Banks (A- to A). The remaining seven reporting regions showed declines in ecosystem health, with Waterloo Bay showing the most significant reduction in grade (A to a D+). These results emphasis the need to understand the resilience of Moreton Bay to cope with extreme pressures brought about by high rainfall events.