Environmental issues

Water quality

Water quality

Tools for water quality managers to protect public health, support the economy and maintain a rich ecosystem.

Water quality is fundamental for good river health. Water quality sustains ecological processes that support native fish populations, vegetation, wetlands and birdlife.

Similarly, many of our own uses depend on water quality that is suitable for irrigation, watering stock, drinking, fishing and recreation, and to meet cultural and spiritual needs.

The Office of Environment and Heritage (OEH) has a lead role in developing environmental objectives for water quality and river flows for government and providing a framework for councils to develop stormwater management objectives. To assist in better management of water quality, OEH has developed a number of resources and tools for water managers, including local councils, and catchment management authorities.

Water Quality Objectives recognise the environmental values and uses for different waterways that the community want to see protected. These include recreational use, healthy aquatic ecosystems, and water for drinking and irrigation. Following consultation with communities, these objectives have been established for surface waters. A similar process was followed to develop Marine Water Quality Objectives.

Water quality is managed and assessed in terms of indicators for levels of bacteria and the resources below are aimed to assist in this regard. River flow objectives are the 'ideal' natural flow conditions that will improve river health and water quality.

What is water quality?

Water is essential to human life and the health of the environment. As a valuable natural resource, it comprises marine, estuarine, freshwater (river and lakes) and groundwater environments that stretch across coastal and inland areas. Water has two dimensions that are closely linked: quantity and quality. Water quality is commonly defined by its physical, chemical, biological and aesthetic (appearance and smell) characteristics. A healthy environment is one in which the water quality supports a rich and varied community of organisms and protects public health.

Water quality in a body of water influences the way in which communities use the water for activities such as drinking, swimming or commercial purposes. More specifically, the water may be used by the community for:

  • supplying drinking water
  • recreation (swimming, boating)
  • irrigating crops and watering stock
  • industrial processes
  • navigation and shipping
  • production of edible fish, shellfish and crustaceans
  • protection of aquatic ecosystems
  • wildlife habitats
  • scientific study and education.

Why is water quality important?

Our water resources are of major environmental, social and economic value to NSW, and if water quality becomes degraded this resource will lose its value. Water quality is important not only to protect public health: water provides ecosystem habitats, is used for farming, fishing and mining, and contributes to recreation and tourism.

If water quality is not maintained, it is not just the environment that will suffer. The commercial and recreational value of our water resources will also diminish.

What affects the quality of our water?

Water quality is closely linked to the surrounding environment and land use. Other than in its vapour form, water is never pure and is affected by community uses such as agriculture, urban and industrial use, and recreation. The modification of natural stream flows by dams and weirs can also affect water quality. The weather, too, can have a major impact on water quality, particularly in a dry country like Australia which is periodically affected by droughts.

Groundwater is a major source of water in NSW, with reserves estimated to be 200 times more than the water in dams. Groundwater is an integral part of our water supply. At times of low river flow, groundwater enters the rivers, maintaining river flow. Although data on groundwater quality is limited, it is clear that, like other bodies of water, groundwater close to urban or industrial development is vulnerable to contamination.

Generally the water quality of rivers is best in the headwaters, where rainfall is often abundant. Water quality frequently declines as rivers flow through regions where land and water use are intense and pollution from intensive agriculture, large towns, industry and recreation areas increases.

Of course, there are exceptions to the rule and water quality may improve downstream, behind dams and weirs, at points where tributaries or better quality groundwater enter the main stream, and in wetlands.

Rivers frequently act as conduits for pollutants by collecting and carrying wastewater from catchments and, ultimately, discharging it into the ocean. Stormwater, which can also carry heavy loads of nutrients, organic matter and pollutants, finds its way into rivers and oceans, mostly via the stormwater drain network. Beach water quality in NSW may also be affected by bacteria from sewer overflows or other runoff into stormwater drains.

How is water quality measured?

The presence of contaminants and the characteristics of water are used to indicate the quality of water. These water quality indicators can be categorised as:

  • Biological: bacteria, algae
  • Physical: temperature, turbidity and clarity, colour, salinity, suspended solids, dissolved solids
  • Chemical: pH, dissolved oxygen, biological oxygen demand, nutrients (including nitrogen and phosphorus), organic and inorganic compounds (including toxicants)
  • Aesthetic: odours, taints, colour, floating matter
  • Radioactive: alpha, beta and gamma radiation emitters.

Measurements of these indicators can be used to determine, and monitor changes in, water quality, and determine whether it is suitable for the health of the natural environment and the uses for which the water is required.

The design of water quality monitoring programs is a complex and specialised field. The range of indicators that can be measured is wide and other indicators may be adopted in the future. The cost of a monitoring program to assess them all would be prohibitive, so resources are usually directed towards assessing contaminants that are important for the local environment or for a specific use of the water.

This water quality information can then be used to develop management programs and action plans to ensure that water quality is protected.

How does water quality affect aquatic ecosystems?

An ecosystem is a community of organisms – plants, animals, fungi and bacteria – interacting with one another and the environment in which they live. Protecting aquatic ecosystems is in many ways as important as maintaining water quality, for the following reasons:

  • Aquatic ecosystems are an integral part of our environment. They need to be maintained if the environment is to continue to support people. World conservation strategies stress the importance of maintaining healthy ecosystems and genetic diversity.
  • Aquatic ecosystems play an important role in maintaining water quality and are a valuable indicator of water quality and the suitability of the water for other uses.
  • Aquatic ecosystems are valuable resources. Aquatic life is a major source of protein for humans. In most countries, including Australia, commercial and sport fishing is economically important.

How does water work?

This diagram illustrates the variety of physical processes related to the movement and storage of water within the environment.

movement and storage of water within the environment processes

What can be done to improve water quality?

The NSW Government participated in developing the National Water Quality Management Strategy (NWQMS). This strategy provides a framework for action and a series of guidelines and scientific criteria that will help improve water quality.

As part of the NSW Government's water reform, water quality objectives for each catchment in the state were developed. The objectives use the method developed by the NWQMS.

The NSW Government has also established other processes to coordinate water quality management programs across all State Government agencies. Some of the key initiatives that OEH is involved with are:

  • providing information to the public on the quality of water through the Beachwatch, Harbourwatch and Hawkesbury-Nepean water quality programs and the State of the Environment reports
  • developing environmental education programs that help the community understand how their actions affect water quality
  • supporting total catchment management programs, as well as providing financial resources to communities through grants programs such as the NSW Environmental Trust
  • developing pollution reduction programs and regulating industrial activities, as well as controlling diffuse sources, to prevent water pollution
  • working with the community to tackle difficult water quality problems, such as stormwater pollution and urban runoff
  • working together with other government agencies, water boards and local councils to develop and implement effective water quality management strategies.

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Page last updated: 12 May 2017