Adelaide coastal waters

Study focus area of Gulf St Vincent (Photo credit: DENR) The Adelaide coastal waters include the Port waterways and metropolitan beaches, and extend from Sellicks Beach in the south to Port Gawler in the north. They include the waters approximately 20 km offshore.

Adelaide coastal waters make up part of the Gulf St Vincent and include areas of seagrass and subtidal reef environments supporting important feeding grounds and nurseries for fish, crustaceans, molluscs and marine mammals.

Maintaining good water quality is essential for the maintenance of these marine habitats and important for industry and the recreational uses of Adelaide coastal waters and metropolitan beaches.

What are the problems facing Adelaide coastal waters

Historically the area of the Port River and the broader area of Adelaide coastal waters have been impacted by poor water quality from discharges from industry, wastewater and stormwater. The EPA has previously studied and monitored water quality in this area quite extensively.

The EPA established the Adelaide Coastal Waters Study (ACWS) in 2001 in response to concerns about the decline in coastal water quality and loss of more than 5,000 hectares of seagrass, around 200 times the area of the playing grounds at the new Adelaide Oval.

The ACWS final report summarises the key findings highlighting that discharges into Adelaide coastal waters from wastewater treatment plants, industry and stormwater outlets are high in nutrients and suspended solids and were causing loss of seagrass along the Adelaide coastline.

The study revealed that there needed to be a 75% reduction in nutrients, specifically nitrogen, and a 50% reduction in suspended solids for there to be a return of seagrass. In general, the industrial sources contribute the most nutrient, while stormwater is the bigger contributor of suspended solid pollution to the coast.

What has been done to improve water quality in the Adelaide coastal waters

The EPA completed the Port Waterway Water Quality Improvement Plan in 2008 which is focused on water quality improvement for the Port Waterways.

To further the recommendations from the ACWS and provide a long-term strategy to achieve and sustain water quality consistent with community expectations for Adelaide’s coastal waters, the Adelaide Coastal Water Quality Improvement Plan (ACWQIP) was released in mid-2013. The plan was a culmination of over 5 years of work on consultation with key stakeholders and the community for the improvement of water quality along Adelaide's coastline.

The ACWQIP was developed in partnership with relevant government agencies, business and industry. A summary overview of the ACWQIP has been provided for your information.

The ACWQIP includes 8 strategies which are underway in partnership with key stakeholders and the community:

reduce nutrient, sediment and coloured dissolved organic matter (CDOM) discharges
promote integrated use of wastewater and stormwater across Adelaide
further investigate sources and volumes of sediment and CDOM
integrate monitoring for cumulative impact assessment across the Adelaide region
model and evaluate the impacts of climate change, new human impacts and population growth implications for Adelaide coastal waters
establish planning and funding priorities for water initiatives for Adelaide’s coastal waters
undertake seagrass mapping and rehabilitation work
build community capacity to take action to improve coastal water quality.

In the ACWQIP the EPA is identified as the agency to lead the reduction of nutrients from point source discharges from the wastewater treatment plants operated by SA Water and (the now closed) Penrice Soda Products. However, addressing the issues associated with stormwater involves many players and needs a more integrated approach.

Catchment to Coast focus for water quality improvement across urban Adelaide

Between 2013 and 2018 the EPA implemented many of the strategies in the ACWQIP with funding of $2 million from the Australian Government National Landcare Program.

The 'Catchment to Coast focus for water quality improvement across urban Adelaide’ concentrated on building community capacity for water quality improvement as its main strategy. The project involved on-ground action, signage at specific sites and some monitoring to inform managers of stormwater on how to best reduce sediment, coloured dissolved organic matter (CDOM) and nutrient loads from stormwater in the Adelaide region.

Through 6 sub-projects, improvements to Adelaide's urban waterways and coastal waters led to implementation of strategies 1, 3, 4 and 8 from the Adelaide Coastal Water Quality Improvement Plan (ACWQIP) which:

provided information through the steering group and online communities such as Water Sensitive SA
supported community awareness and education of catchment to coast issues through activities with the Marine Discovery Centre
developed water sensitive urban design (WSUD) demonstration sites with the City of Unley, City of West Torrens and Adelaide City Council
collaborated with the Kaurna people of the Adelaide region
managed Rain Garden 500, a 3-year devolved grant program
monitored water quality across catchments and subcatchments in Adelaide.

The EPA worked in partnership with other agencies and local government to support implementation of water sensitive urban design (WSUD) and better sediment management across the Adelaide region to improve coastal water quality

Increasing our understanding of stormwater discharge to Adelaide coastal waters

In 2005, as part of the ACWS, an audit report was commissioned to investigate the available data in the ACWS area and identify data gaps. The report summarised the monitoring programs undertaken in the ACWS and provided recommendations for future monitoring programs. In 2015 another audit was undertaken to summarise the data collected in the 10 years since the last audit.

The report noted that:

The availability and quality of flow and water quality data has improved substantially since the previous audit and this improvement has made comparisons between this and the earlier audit complex.
Water quality monitoring was not performed at all sites for the reporting period, and a reduced period of 2009–14 was used as the data set for water quality.
There are still gaps in the data for the southern coastal catchments, the Patawalonga Coastal stormwater drainage systems (Holdfast drains) and the Buckland Park Lake (Gawler River discharge).
Data in later years included environmental flows – controlled releases of water into some rivers in the system to improve overall catchment health

Although it is difficult to compare the two audits, the 2015 report may indicate some trends. Monitoring into the future will assist in consolidating trends. Some possible trends are:

Overall there is an increase in stormwater outflows. Taking into account environmental flows, there is still an upward trend in flow volumes into Gulf St Vincent. This upward trend occurred despite significant years of very low rainfall.
Generally pollutant loads increase as flow volumes increase.
While only 5 years of consistent data on water quality is available, this data shows that the majority of pollutants were discharged through the Torrens, Gawler and Onkaparinga Rivers and the Barker Inlet Wetland.
The 3 river systems, Torrens, Gawler and Onkaparinga account for over 50% of the total pollutant loads.
The Torrens River is the most significant catchment contributor for both total suspended solids and total nitrogen contributing 36% and 30% respectively.

Water quality monitoring of nearshore marine waters

The EPA's water quality monitoring program is now focused on a monitoring, evaluation and reporting program (MERP) for aquatic ecosystems which assesses the condition of seagrass and reef habitats in Gulf St Vincent.

This monitoring information is released as Aquatic Ecosystem Condition Reports (AECRs), and provides a better indication of what is happening for Adelaide coastal waters in terms of water quality and condition of seagrass and reef areas, identify pressures on the condition, and helps the EPA to work with industry, local government and other relevant state government agencies to manage and improve that condition.

Further information