Chapter 5: Water

5.6 Marine and estuarine water quality

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5.6 Marine and estuarine water quality

Marine and estuarine recreational water quality continues to improve in the Sydney, Hunter and Illawarra regions, but remains poor in some other NSW estuaries and deteriorates after wet weather

Greatly improved recreational water quality in dry weather for the Sydney, Hunter and Illawarra regions demonstrates effective water quality management in these densely populated urban areas. Wet-weather conditions, however, remain a problem, with contaminated stormwater sometimes making beaches unfit for swimming.

There is good information on recreational water quality in Sydney, and the Hunter and Illawarra, while the status and distribution of many marine and estuarine pollutants elsewhere in NSW is unknown. Information currently available suggests that estuarine water quality may be deteriorating in some areas following a decline in aquaculture and fisheries since 1997. Acid sulfate soil runoff has also been identified as an important water quality issue for estuaries in NSW.

While no major marine oil spills have occurred in NSW since 1999, pollutant spills from land-based sources and minor spills from vessels continue in marine and estuarine waters.

NSW Indicators


Status of Indicator

5.10 Exceedences of marine and estuarine primary contact recreational water quality guidelines

Compliance with recreational water guidelines improved for many Sydney, Hunter and Illawarra ocean beaches in 2001–02. Compliance is lower during wet weather, indicating that stormwater inputs and sewage overflows remain a source of marine and estuarine pollution.

5.11 Point-source discharges to marine and estuarine waters, and wastewater treatment

The marine waters off highly urbanised areas, particularly Sydney, receive significant loads of nutrients from sewage treatment plants. However, current data suggests the impacts are low.

5.12 Marine and estuarine algal blooms

Reports of potentially harmful or toxic algal blooms have remained stable between 1994 and 2002. Reports of harmless algal blooms have varied with no clear trend. Some studies are suggesting that the occurrence of blooms is increasing.

5.13 Major marine and estuarine pollution incidents

There have been no significant marine oil spills since August 1999. Two significant land-based spills of toxic substances have occurred, causing significant ecological damage to estuarine ecosystems in the Sydney region.

Importance of the issue

Marine and estuarine waters support dynamic ecosystems, contain valuable natural resources, and have important environmental values. The quality of these waters is affected by pollution from point and diffuse sources, spills from shipping accidents, land-based spills that reach coastal waters, and discharges from vessels. Pollution occurs directly or through rivers that flow into these coastal waters.

River regulation also affects coastal water quality, particularly estuaries and coastal lakes, by reducing the high flows required to disperse pollutants and sediment. In extreme cases reduced flows can lead to river mouths being severely restricted or closed by a build-up of sediment. This can interfere with the chemical, biological and physical interactions between marine and freshwater ecosystems and cause pollutants to accumulate.

Many NSW beaches that were previously affected by pollution have become much cleaner in recent years. However a number of estuaries and coastal lakes are under intense urban, industrial and recreational development pressure. This is because over 85% of the population lives in coastal areas and more than 80% live near an estuary (Human Settlement 2.1; NLWRA 2002b). This pressure can be detrimental to the quality of coastal waters with impacts on ecosystem health, the productivity of fisheries and aquaculture, human health and recreational amenity.

The Healthy Rivers Commission, for example, identified poor water quality as the primary reason for a decline in oyster production in the late 1990s (HRC 2003). The National Land and Water Resources Audit (NLWRA) has also reported that NSW oyster production (worth $29 million in 1999–2000) fell by 350 tonnes in the three years to 2000, a decline mostly related to poor estuarine condition and bacterial contamination (NLWRA 2002b). The downturn in oyster production indicates that estuarine water quality is generally deteriorating in many areas of NSW.

The NLWRA has also reported that the tonnage of fish harvested from NSW estuaries declined substantially between 1997–98 and 1999–2000 from 1039 tonnes to 742 tonnes (see Biodiversity 6.9).

A Healthy Rivers Commission inquiry reported that most NSW coastal lakes are affected by, or are under considerable pressure from, agricultural and urban runoff, urban development, sewage and industrial pollution (HRC 2002). The Australian State of the Environment Report 2001 suggests that the maintenance or restoration of water quality in the nation's coastal margins is arguably one of the most critical marine environmental issues (Australian State of the Environment Committee 2001).

For more information on marine and estuarine ecosystems and values, see EPA 2000a, EPA 2000c and Biodiversity 6.6. For more information on marine and estuarine pollution incidents, see EPA 2000c.

Sources of pollution

Point-source pollution

The concentration of people and industry near the coast means most wastewater is discharged by sewage treatment plants (STPs) into ocean and estuarine environments. Discharges can affect water quality and degrade marine and estuarine environments. Estuaries or lakes are much more sensitive than the ocean. These impacts include decreased diversity and abundance of intertidal and subtidal species, the domination of marine ecosystems by species adapted to nutrient-rich environments, and small increases in the concentrations of metals and other contaminants in sediments and marine species.

Although STPs are the largest continuous source of pollution discharged to coastal waters off Sydney, most studies into the deep ocean outfalls which transport the sewage suggest there has been no serious environmental impact from these discharges (AWT 2000; AWT 2001a; AWT 2001b; SWC 2001; Water 5.7). However, the long-term viability of the use of the outfalls is yet to be demonstrated because of the indirect and possibly accumulative effects of a number of subtly acting substances such as hormone mimics (Australian State of the Environment Committee 2001).

Diffuse-source pollution

Runoff from acid sulfate soils has been identified as an important water quality issue for NSW estuaries and coastal waters (see EPA 2000c). Changes in water pH can severely damage ecosystem health, water quality, fishing, aquaculture and infrastructure. Runoff of de-oxygenated water from acid sulfate soils was implicated in the deaths of hundreds of thousands of fish and other aquatic organisms in the Richmond, Clarence and Macleay rivers on the NSW North Coast in February 2001 (see also Land 4.5). The Richmond and Macleay rivers had to be closed to fishing for five months to aid recovery. The estimated cost of acid sulfate soils to the State's fishing industry ranges between $2.2 and $23 million per year (DLWC 2002).

Marine and estuarine water quality

The NLWRA has assessed the condition of NSW estuaries (NLWRA 2002b). The audit examined the impacts of human activities on 133 NSW estuaries and found that the condition of 10% was almost pristine, 38% largely unmodified, 26% modified and 26% extensively modified. The greatest concentration of extensively modified estuaries occurs in areas of poor catchment and river condition, such as central NSW (Hunter river basins to the Wollongong coast) and larger basins, particularly in northern NSW. The State has five times fewer almost-pristine estuaries, and twice as many modified and extensively modified estuaries as the national average.

Many NSW estuaries have been degraded by poor catchment management practices in the past which have adversely affected coastal water quality. It is estimated that 60% of the State's estuarine wetlands, which protect estuary water quality, have been lost since European settlement. The audit identified the key pressures on coastal water as excess nutrients, sedimentation, habitat loss, changes to natural flows and tidal flushing, pathogens and toxicants (heavy metals, pesticides and polychlorinated biphenyls), introduced pests, and modifications to ocean entrances.

Recreational water quality

Information on NSW marine and estuarine water quality is mostly limited to the monitoring of recreational water quality in the highly urbanised Sydney, Hunter and Illawarra regions by the EPA Beachwatch and Harbourwatch programs. This recreational water quality data provides the community with information on the risks of sewage and stormwater pollution at beaches. Two bacterial indicators, faecal coliforms and enterococci, are used to assess recreational water quality. Although the monitoring of water for recreational use does not provide an assessment of overall water quality and ecosystem health, changes in recreational water quality through time enables an assessment of the effectiveness of stormwater and wastewater management.

The Beachwatch and Harbourwatch results reported below indicate that increases in pollution from sewage overflows and stormwater during wet weather, as well as the capacity of water bodies to dilute pollution, are key determinants of marine and estuarine recreational water quality. Detailed results for each of the 129 beaches monitored in the Sydney, Hunter and Illawarra regions can be found in the Beachwatch and Harbourwatch State of the Beaches report series (EPA 1999; EPA 2000d; EPA 2001; EPA 2002b).

The water quality at Sydney ocean beaches has vastly improved since the commissioning of the Sydney deep ocean sewage outfalls in the early 1990s.The percentage of beaches complying with Beachwatch water quality criteria in the 2001–02 summer was the highest yet recorded.

The most dramatic improvements in beach water quality occurred at the Cronulla area beaches as a result of the upgrade to the Cronulla STP in April 2001. In 2000–01, only one of the eight Cronulla beaches complied with enterococci criteria more than 90% of the time, while a year later seven complied.

High levels of rainfall in 2000–01 resulted in low compliance with Beachwatch water quality criteria for enterococci during wet-weather periods. This was also the case in 1998–99 and 1999–2000 (see EPA 2000b).

Bathing sites at Sydney harbour and estuarine beaches have a lower level of compliance than the city's ocean beaches. This is because harbour and estuarine waters generally have more sewage overflow and stormwater inputs, reduced rates of tidal flushing and less water available to dilute pollution inputs, particularly in the upper reaches.

The percentage of harbour and estuarine bathing sites complying with criteria for enterococci has consistently increased each year since 1998–99, although in that year only 4% of sites achieved a compliance of 90% or higher because of wet weather (see EPA 2000b). Enterococcal compliance for 2001–02 was the best yet recorded.

The percentage of harbour and estuarine beaches complying with faecal coliform criteria more than 90% of the time in 2001–02 was lower than that recorded in the previous two years.

In summer 2001–02, all Hunter beaches complied more than 90% of the time with the criteria for both bacterial indicators. Hunter region beaches continue to be the cleanest group monitored by Beachwatch with high compliance results since 1996–97.

Over the last two summer seasons, the Illawarra beaches have also had a high rate of compliance with swimming guidelines. These results are an improvement on 1999–2000, when high levels of rainfall resulted in pollution from stormwater and STP bypasses in the Illawarra (see EPA 2000b).

Other marine and estuarine water quality

Sydney Water also monitors the estuaries and lagoons within its area of operations (SWC 2001). A range of water quality and biological parameters are assessed to determine water quality. Observations based on the monitoring in 2000–01 include:

  • Water quality in Sydney's estuaries is usually better in the main channel and open bays and becomes worse with distance upstream. This indicates that tidal flushing by ocean water plays an important role in maintaining water quality.
  • Estuarine water quality was found to deteriorate in wet weather suggesting that stormwater runoff from highly developed catchments and discharges from the sewer system are major contributors to the poor water quality.
  • Similar results were found for coastal lagoons where water quality was largely determined by the level of urban and industrial development in the catchment and the frequency of tidal exchange.

Algal blooms

Most marine and estuarine algal blooms are harmless, resulting only in a discolouration of the water. However, some blooms can be toxic to aquatic organisms and humans or potentially harmful by decreasing oxygen levels in the water. Although the causes of marine and estuarine algal blooms are not fully understood, both climate conditions and natural and human-induced fluctuations in nutrient concentrations and loads are considered to be major influences on algal populations.

EPA data indicates that between July 1994 and December 2002, the number of potentially harmful or potentially toxic marine algal blooms reported remained constant. In 2001–02, all but one of the reported blooms occurred in the Sydney region. There were also reports of harmless blooms from various different locations across the NSW marine and estuarine environments.

Reports of visible blooms, together with scientific investigations off Port Hacking, indicate an unprecedented frequency in the occurrence of blooms of one of the more harmless species, Noctiluca scintillans, over the past decade (Ajani et al. 2001). In addition, new harmful algal species have recently been found in Australian waters that had previously only been reported overseas. Ballast water and sediments discharged into Australian waters and harbours by international shipping have been implicated in the colonisation of new algal species (see Biodiversity 6.8 and EPA 2000c).

Responding to concern about the apparent increase in marine algal blooms, the EPA investigated the relationship between nutrient loadings to coastal waters and the development of marine algal blooms. The project found that even though STP discharges are the largest continuous source of nutrient discharges to the coastal waters off Sydney, marine algal blooms did not appear to be influenced by the major outfalls (Pritchard et al. 1999). Weather patterns and the natural upwelling/uplifting of nutrient-rich water were found to be the principal cause of offshore blooms and are likely to account for much of the year-to-year variability in their occurrence.

Pollution incidents

Major pollution incidents have a range of sources. These include shipping accidents resulting in oil or chemical spills, spills on land that drain to marine and estuarine waters, release of sewage from vessels, and ballast-water discharges containing marine pests.

The impacts of pollution incidents vary with their type and location. Examples include:

  • impacts on intertidal biota, fish and bird life from oil spills
  • death of marine biota or contamination of fish stocks and aquaculture from toxic chemical spills
  • displaced native species from marine pests introduced by ballast-water discharges (see Biodiversity 6.8)
  • toxicity to humans and other organisms from introduced species.

The detection of marine and estuarine pollution incidents relies on reports from the general public and commercial and government organisations. The frequency and extent of incidents is therefore likely to be under-reported. Because many pollution incidents originate from land-based sources, it can also be difficult to determine their exact cause. For these reasons, identifying trends in pollution incidents is difficult.

The Australian Maritime Safety Authority maintains a database of reported marine and estuarine pollution incidents. The number of incidents in NSW has been steady between 1996 and 2001 with no visible trends to suggest any increase or decrease in incidents is occurring. The last significant oil spill was from the Laura D'Amato into Sydney Harbour in August 1999 (see EPA 2000b). Between 1996 and 2001, there have been about 12 incidents per year originating from commercial shipping and discharging heavy oil or diesel. The majority of reported pollution incidents have been minor oil spills in Sydney Harbour and Botany Bay, most likely from land-based sources. However, the cumulative and long-term impacts of these minor spills may be significant.

Since NSW State of the Environment 2000 (EPA 2000b), two significant land-based incidents involving toxic substances have occurred in the Sydney region, causing severe ecological damage to estuarine ecosystems:

  • In February 2001, a major pesticide incident contaminated Manly Lagoon killing many fish and invertebrates. An estimated 10,000 dead fish were collected.
  • In February 2002, 1000 litres of insecticide was spilt and flowed into Prospect Creek, which drains into the Georges River. The spill formed a concentrated plume and travelled down Prospect Creek, killing over 2000 fish and other animals.

Response to the issue

The main responses to marine and estuarine water quality issues are programs to reduce the pollution which enters waterways. Responses aimed specifically at marine and estuarine water quality and reducing pollution include:

  • water quality objectives and strategies
  • programs to reduce pollution from major point sources
  • programs to reduce pollution from diffuse sources
  • programs to prevent and manage pollution incidents.

Water quality objectives and strategies

Interim environmental objectives for water quality and river flows were developed for NSW estuaries and coastal rivers as part of the water reform program (EPA 2000f). More recently, quality objectives specifically for NSW coastal marine waters have been released and these should strengthen the consideration of water quality in coastal planning and management.

The marine water quality objectives are a key element of the Coastal Water Quality Management Strategy prepared as part of the NSW Government's Coastal Protection Package announced in June 2001. The strategy is designed to manage coastal water quality in order to protect aquatic ecosystems, recreational water quality and the human consumption of aquatic foods. Other components of the strategy are:

  • a pilot recreational water quality monitoring program, which provides clear, accessible recreational water quality information for waterway users beyond the existing Sydney–Newcastle–Wollongong program
  • a program focusing on the risk assessment of shellfish harvest areas to make sure water quality is suitable for growing oysters, mussels and other shellfish.

The Healthy Rivers Commission has conducted inquiries in a number of coastal catchments and recommended environmental objectives and practical strategies to achieve them. Inquiries have been completed for the Williams, Hunter, Hawkesbury–Nepean, Clarence, Shoalhaven and Bega rivers, the North Coast rivers, and the Georges River–Botany Bay system. An inquiry into coastal lakes has also been completed. Government Statements of Intent, in response to these inquiries, commit agencies to strategies that will improve river and estuary health.

Catchment Blueprints, prepared as part of the NSW Salinity Strategy, contain targets for nutrients and other water quality problems relevant to the management of coastal lakes and estuaries.

Estuary management plans have also been prepared with the objective of improving sustainable planning and management practices, and protecting and conserving sensitive estuary ecosystems. Strategies for protection and improvement of estuary water quality form part of these plans. Forty estuary management plans are being implemented throughout the State.

Programs to reduce pollution from point sources

The framework for managing point-source pollution of marine and estuarine waters is the same as the framework for discharges to fresh waters outlined in Water 5.3. Of particular relevance to marine waters is the recent change to licensing of complete sewage treatment systems rather than only STPs. This includes all associated components of the reticulation system, including pipes and overflow structures. The licences contain a range of operating and maintenance requirements as well as pollution reduction programs to improve the performance of both the treatment plant and the reticulation system.

To help prevent sewage overflows in Sydney Harbour, the NSW Government funded construction of the $450-million Northside Storage Tunnel. This has reduced overflows by 80–90% and prevented over 5 billion litres of diluted sewage from entering the harbour.

Through the National Pollutant Inventory (NPI), industrial emitters across Australia are required to report annually on estimated emissions of 90 pollutants to water, air or land. The NPI aims to encourage industry to identify and change certain manufacturing processes to make them cleaner or more efficient.

A range of other programs is improving the management of effluent from STPs including:

  • the Country Towns Water Supply and Sewerage Program, which helps country councils develop better water and sewerage services (DLWC 1999a)
  • the Priority Sewerage Program, which identifies priority areas for sewerage system improvements from an environmental and human health perspective within the operating boundaries of Sydney Water, Hunter Water, and Gosford and Wyong Councils
  • the NSW Government's Waterways Package including the $90-million upgrade of the Cronulla STP completed in April 2001 and the $197-million Illawarra Wastewater Strategy to transfer wastewater from Bellambi and Port Kembla STPs to Wollongong STP for treatment or reuse.

Programs to reduce pollution from diffuse sources

The framework for managing diffuse-source pollution of marine and estuarine waters is the same as the framework for discharges to fresh waters outlined in Water 5.3. There has been considerable activity in recent years to reduce pollution from urban stormwater runoff, but less effort to date has gone into reducing runoff from agricultural sources, with the exception of acid sulfate soils (see Land 4.5).

In September 2002 the Waterways Authority introduced a strategy to manage sewage pollution from vessels in all NSW waterways. Key actions include:

  • requiring commercial passenger vessels and houseboats to install toilets and holding tanks
  • designating certain waterways and specific areas within waterways 'no-discharge zones' for treated sewage
  • prioritising applications for pump-out facilities
  • implementing an education campaign to inform the boating community of its responsibilities in managing sewage pollution from vessels.

In addition, the NSW Government has increased the penalties for polluting waterways to $500,000 for individuals and $10 million for corporations.

Programs to prevent and manage pollution incidents

The body responsible for preventing or responding to major pollution incidents varies with the type of incident. There are two plans for the management of marine and estuarine pollution incidents in NSW:

During major spills, these plans provide for a coordinated response from many organisations to clean up the spill, thereby minimising the impact on human health and the marine environment.

Other programs

The Coasts and Clean Seas Program funded a range of projects between 1997 and 2002 to conserve, repair and encourage the sustainable use of NSW's coastal and marine environments. Projects covered the management of sewage and stormwater pollution, prevention of marine pests and other threats to biodiversity, and marine research. These were funded through a partnership between the Commonwealth's Natural Heritage Trust, the NSW Government, local government, industry, universities and the community. The Department of Infrastructure, Planning and Natural Resources has coordinated the program in NSW, with 14 projects worth $4.65 million in 2001–02.

Programs to manage marine and estuarine algal blooms have also been conducted through the activities of coastal Regional Algal Coordinating Committees.

Effectiveness of responses

There have been significant improvements in recreational water quality in NSW marine and estuarine waters. This demonstrates the effectiveness of recreational water quality management in the Sydney, Hunter and Illawarra regions. Contaminated stormwater remains a problem in wet weather. In time, the licensing of whole sewage treatment systems will help address the sewerage component of the discharges.

The deterioration in estuary condition, combined with a decline in aquaculture, suggests current actions need strengthening if the degradation of estuarine water quality is to be halted.

Most of the responses to water quality management have focused on point sources. The Sydney deep ocean sewage outfalls, for example, have dramatically improved beach recreational water quality. By contrast, pollution from diffuse sources remains the main challenge to achieving better water quality. Although the management of urban stormwater runoff has improved, other sources of diffuse water pollution, such as acid sulfate soil runoff, are still having significant impacts.

The Laura D'Amato oil spill in Sydney Harbour in 1999 showed that responses to major incidents can be effective and well executed. However, two recent land-based toxic spills, and continued reporting of many small oil spills, suggest that additional measures need to be taken to prevent pollution incidents.

Future directions

Increased effort is required to manage water pollution from diffuse sources. Government needs to work with land managers to further explore ways to reduce runoff of pollutants.

Landholders can adopt a range of management changes to reduce the runoff of pollutants. They can also continue to work with agencies to protect and restore riverine corridors to help prevent pollution from entering rivers. More information on sustainable land management practices and financial assistance is available from the Department of Infrastructure, Planning and Natural Resources.

Individuals can make simple changes to their everyday behaviour to help reduce water pollution and protect waterways, for example:

  • not using sinks to dispose of harmful materials, such as oils and grease, medicines and other chemicals
  • composting food scraps or putting them in the bin rather than washing them down the sink
  • using washing detergents with low or no phosphorus and using them sparingly
  • washing cars on the lawn or at a carwash where the water is recycled
  • cleaning up animal waste and disposing of it in the rubbish bin.

The Department of Infrastructure, Planning and Natural Resources, EPA and Sydney Catchment Authority have more information and advice on how to reduce the pollution of waterways.

With much of the risk from larger ocean-going vessels closely monitored, it is often the combined impact of discharges from smaller vessels or land-based sources that threaten the quality of waterways. The boating community can help prevent marine and estuarine pollution by:

  • reporting pollution incidents to the EPA Pollution Line or relevant Port Corporation for oil spills in ports
  • making sure boats and engines are in good working condition and checked regularly for oil and fuel leaks
  • taking care when filling fuel tanks to avoid spills
  • installing a holding tank or an approved on-board sewage treatment system and disposing of its contents at waste receiving facilities at boat ramps and marinas.

The Waterways Authority has more information on how to reduce the pollution of waterways when boating.

Linked issues

2.1 Population and settlement patterns

4.1 Land-use changes

5.2 Surface water extraction

5.3 Surface water quality

5.7 Sediment contamination

6.6 Aquatic ecosystems

6.7 Aquatic species diversity

6.9 Aquatic harvesting