Water quality

Water quality guidelines

The Australian and New Zealand guidelines for fresh and marine water quality are a joint initiative of the Australian and New Zealand governments, in partnership with the Australian states and territories. The objective of the guidelines is to provide authoritative guidance on the management of water quality in Australia and New Zealand. The guidance includes setting objectives for water quality and sediment quality designed to sustain current, or likely future, community values for natural and seminatural water resources.

In 2018, the Australian Government Department of the Environment released the updated and online guidelines (DAWR 2018); the series of updated documents allows for more flexibility in how they are used.

To protect the community values of waterways, the Water Quality Management Framework encompasses key requirements for long-term management strategies (Figure 30):

  • good understanding of links between human activity and water and sediment quality
  • clearly defined community values or uses, including the setting of unambiguous management goals
  • clearly identified and appropriate objectives for water and sediment quality
  • adoption of cost-effective strategies to achieve water and sediment quality objectives.

Figure 30 The 10 steps to implement the Water Quality Management Framework

The Water Quality Management Framework lists the steps for planning and managing water quality or sediment quality:

  • Examine current understanding.
  • Define community values and management goals.
  • Define relevant indicators.
  • Determine water and sediment quality guideline values.
  • Define draft water and sediment quality objectives.
  • Assess if draft water and sediment quality guidelines are met.
  • Consider additional indicators or refine water and sediment quality objectives.
  • Consider alternative management strategies.
  • Assess if water and sediment quality objectives are achievable.
  • Implement agreed management strategy.

One of the updated guidelines supports the development of principles and guidance to preserve and enhance cultural and spiritual values in water planning. Ideally, appropriate upfront and ongoing engagement of relevant Indigenous people is a key element of the process, particularly with regard to ensuring the proper identification, prioritisation and consideration of cultural and spiritual values throughout the water quality planning process (Figure 31). However, these principles have not yet been implemented.

Effective communication with Indigenous people must be based on an understanding of their frame of reference – that is, a holistic approach, with people and all aspects of the environment interconnected. This differs from the usual approach of splitting natural resources management into smaller components, such as water quantity and water quality. To achieve effective communication, this difference must be addressed and, therefore, water quality planning must be linked with:

  • the broader management of the landscape, including water allocation planning, natural resources management, environmental protection, sustainable agriculture and land use, and development controls
  • day-to-day management of land and marine activities by Indigenous people, other community members, agricultural and other industries, and government land managers
  • cultural, economic, social and spiritual considerations that are fundamental to supporting the maintenance and development of Indigenous culture.

Figure 31 Proposed pathways for incorporating cultural and spiritual values into water quality planning


In many parts of Australia, soils, surface water and groundwater have a high salt content due to the dry climate and highly weathered landscape. Across Australia, dryland and irrigated agriculture, and clearing of native, perennial vegetation have changed the catchment water balance. These changes in landscapes increase the mobilisation of highly soluble salts from saline aquifers or shallow water tables into streams. This unnatural increase in salinity can present a risk to aquatic ecosystems and vegetation health (Boulton et al. 2014).

Within the Murray–Darling Basin and in several other areas in Australia, salinity is increasingly managed and monitored through the implementation of jurisdictional Land and Water Management Plans that include water quality. These plans can provide a framework for setting salinity objectives and targets, as well as for developing on-ground measures to improve salinity conditions. Such measures include providing adequate water flows, investing in revegetation, improving irrigation and dryland farming practices, and implementing salt interception schemes that minimise the movement of salts.

To support water quality management and planning, an Australian Government initiative has created the Water Quality Australia website in partnership with state and territory governments. The website provides tools and resources to guide water managers; researchers; industry; and state, territory and local governments in developing and implementing water quality plans and strategies.

Streamflow salinity concentrations determine the suitability of water for various uses (e.g. drinking, irrigation). They can also be an indication of impacts on ecosystems. The broad salinity categories for which water is considered fit for various uses are based on the guidelines provided by the National Health and Medical Research Council (NHMRC & NRMMC 2011) (Table 4).

Table 4 Water salinity and primary suitability for use

Salinity category

Total dissolved solids concentration (mg/L)

Suitability for use



Good-quality water suitable for drinking and all irrigation



Fair- to poor-quality drinking water; suitable for most irrigation; adverse effects on ecosystems may become apparent



Unacceptable-quality drinking water; useful for most livestock; irrigation limited to certain crops



Unacceptable drinking water quality; use may be limited for certain livestock



Seawater salinity or greater; undrinkable; some mining and industrial uses

mg/L = milligrams per litre

Salinity levels vary by region. For example, southern Western Australian streams are naturally more saline than streams in northern Australia and along the eastern divide, where greater rainfall dilutes salt concentrations. In addition, in some areas, the natural salinity has been exacerbated by secondary salinisation such as that caused by irrigation.

Despite the very-low-rainfall conditions that persisted from 2017, the percentage of sites across Australia for each saline category only showed small changes (Table 5; Figure 32). Salinity increased at individual sites, but this did not affect the saline category in which the sites fell. In general, the sites with fresh median water salinities are mostly located in areas with high rainfall along the east coast. In contrast, streams in Western Australia had higher water salinities. Almost three-quarters of the sites in Western Australia were brackish or saline. In South Australia, about a quarter of the sites were brackish or saline.

Table 5 Percentage of sites in each salinity category, 2016–17 to 2019–20
Figure 32 Distribution of median annual streamflow salinity across Australia, 2016–20

Eutrophication and suspended sediments

Eutrophication (excess nutrients in water) is a naturally occurring phenomenon, which is intensified by human activities such as clearing of land, application of fertilisers and dumping of industrial waste. The effects of eutrophication on Australia’s rivers have been increasing since 1991 when more than 1,000 kilometres (km) of the Baaka/Barka – Darling River were affected by an algal bloom that killed hundreds of sheep and cattle, and caused human health impacts. Since then, 4 similar algal blooms have occurred in the Murray, in 2007, 2009, 2010 and 2016 (Baldwin 2016). Between December 2018 and January 2019, 3 significant fish deaths occurred in the Baaka/Barka-Darling River, and algal blooms caused by eutrophication were identified as one of the major causes of the death of more than 1 million fish (Vertessy et al. (2019); see Menindee Lakes).

The burning of an area of more than 170,000 square kilometres (km2) during the 2019–20 bushfires has heightened the potential for development of algal blooms and hypoxic blackwater. Burning of large areas of forest has produced ash-enriched soils, which are highly erodible and will run off into dams and rivers during large rainfall events. The organic carbon in the ash biodegrades in the water, causing deoxygenation and hypoxic blackwater events. Although burned catchments are a major cause of hypoxic blackwater events, such events also occur when flooding washes organic matter such as leaves into rivers. Hypoxic blackwater events can occur in any lowland river system; however, numerous hypoxic blackwater events have occurred in the Murray–Darling Basin during the past decade.

Between October 2019 and May 2020, more than 65 fish death events occurred across the Murray–Darling Basin as a result of run-off from bushfire-affected catchments. Given that early beneficial effects of reforestation of catchments will take several years to be realised, these events will continue.

Case Study Lake Hume and River Murray low dissolved oxygen event, February 2021

Source: MDBA Water Quality Advisory Panel, February 2021

Lake Hume is located near Albury (New South Wales)–Wodonga (Victoria) and is the main operating storage of the River Murray system, supplying water for irrigators, cities and towns, and environmental purposes.

During the 2019–20 bushfires, approximately 32% of the Lake Hume catchment was severely burned, making it highly susceptible to increased mobilisation of sediment, ash, nutrients and other contaminants following rainfall events.

In February 2021, significant rainfall was recorded across the bushfire-affected areas of the upper Murray, resulting in run-off containing large amounts of ash, sediment and debris. It also contained large amounts of dissolved organic carbon, iron, manganese and nutrients.

With seasonally warmer temperatures, this material triggered biological and chemical processes within Lake Hume that saw development of a significant layer of water with very low dissolved oxygen.

Across the warmer months, Lake Hume typically becomes layered with thermally stratified water. During the event, the water with little or no dissolved oxygen occurred in a layer at a depth of approximately 20 m, which is around the same level as the Hume Dam offtakes.

This resulted in water being released with low dissolved oxygen levels into the River Murray immediately downstream from Hume Dam with the following impacts:

  • Murray crayfish reported to be crawling out of the water in response to low dissolved oxygen
  • ‘rotten egg’ odour (hydrogen sulfide) and orange staining of vegetation and some of the crayfish due to oxidation of iron and manganese
  • water quality supply issues reported by Albury City Council, with ‘rotten egg’ odour and discolouration.

The Murray–Darling Basin Authority responded by adjusting operations to assist with aeration of the water, and applying compressed air to water flowing through the Hume Dam hydropower station.

Ongoing response includes upgrades to upstream and downstream water quality monitoring sites, adaptive management of releases (if required) and engagement of water quality expertise to quantify potential risks.

Per- and poly-fluoroalkyl substances (PFAS)

Per- and poly-fluoroalkyl substances (PFAS) are a group of human-made chemicals that have been used since the 1950s in nonstick cookware, waterproof clothing and fabric stain protection. However, the most problematic use of PFAS has been in aqueous film-forming foam (AFFF), which is used to fight liquid fuel fires.

From the 1970s, AFFF was used by the defence forces for firefighting activities and firefighting training. As a consequence, increased PFAS levels have been detected at defence bases, most notably those at Williamtown in New South Wales, Oakey in Queensland, and Katherine in the Northern Territory. Other affected sites include airports and locations where firefighting training takes place.

Increased levels of PFAS are known to be toxic to a range of animals; however, the impact on human health is unknown. The Australian National University was commissioned by the Australian Government to undertake a PFAS Health Study to examine possible links between PFAS exposure and health in communities in Williamtown, Oakey and Katherine. The study is due for completion in mid-2021; initial findings have found links between high cholesterol levels and higher levels of PFAS, and possible links with reduced kidney function, testicular cancer, and the immune response to diphtheria and rubella vaccines (Kirk et al. 2018, Banwell et al. 2019).

In light of the uncertainties associated with the potential risks of PFAS, a precautionary approach to protect the environment and human health was developed. This took the form of the PFAS National Environmental Management Plan 2018 (HEPA 2018), which provided guidance on the regulation of PFAS-contaminated sites, and materials and products. Version 2 of the plan, released in 2020, provided guidance on environmental guideline values, soil re-use, wastewater management and onsite containment, which had been identified as priorities in version 1 (HEPA 2020). In May 2020, the National PFAS Position Statement was endorsed by most Australian states; subsequently, New South Wales implemented a progressive ban on PFAS in March 2021, following similar bans put in place by Queensland in 2016 and South Australia in 2018.

It should be noted that, although firefighting foams were used during the 2019–20 bushfires and that these will have ecological impacts (Adams & Simmons 1999), AFFF containing PFAS were not used because it is used for fighting liquid fires and not bushfires.

Acid sulfate releases

Acid sulfate releases occur when acid sulfate soils are disturbed by human activities such as drainage works or excavations. They also occur during extended dry periods when water levels in wetlands, swamps and mangrove forests fall and acid sulfate soils are exposed to the air, releasing sulfuric acid and soluble iron into waterways. This results in reduced pH levels (i.e. the water is more acidic) and decreased dissolved oxygen. These conditions kill plants and immobile aquatic species such as oysters, cause red-spot disease in fish, and damage animal habitats.

An acid sulfate release occurred in the Coorong and Lakes Alexandrina and Albert in South Australia when low water levels exposed more than 20,000 hectares of acid sulfate soils, causing the soil and water to become acidic. This endangered the Ramsar wetlands in the Coorong and the Lakes, and threatened the flora and fauna that live in the aquatic and terrestrial ecosystems. The event led to the preparation of the Drought Emergency Framework for Lakes Alexandrina and Albert by the Murray–Darling Basin Authority (MDBA 2014).

To better manage acid sulfate soils and mitigate the risk of future acid sulfate releases, the Australian Government and the National Committee for Acid Soils have prepared national guidelines for acid sulfate soils (Sullivan et al. 2018). These guidelines complement those already implemented in states with significant areas of acid sulfate soils. Most guidelines focus on identifying and mapping acid sulfate soils to avoid future disturbance; however, where acid sulfate soils have been disturbed, they can be treated by adding an alkaline material to neutralise the acidity.