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Water type and quality

Pure water has no nutrients, sediments and is totally colourless and tasteless[2]. However, water in wetlands has a range of different characteristics, some are due to the natural variation in the substrate and surrounds and others to human activities (anthropogenic influences). The water type fundamentally affects what lives in the wetland and how the wetland functions and supports values.

Wetland water type attributes are used when applying the Queensland wetland habitat classification scheme to lacustrine and palustrine wetlands.

McEwens Beach—brackish area Photo by Chris Small

Quick facts

Brackish water
is water that is not quite fresh and not quite seawater. It may be from saltwater mixing with fresh water or from fresh water gaining salt from the surrounding environment.

Lake Wyara Photo by DES

Marine and estuarine wetlands contain saline water due to their links with oceanic water. Other wetland systems may contain saline water as a result of their substrate or water source, e.g. some spring fed wetlands have high levels of salts and other minerals.

Other aspects of water type such as pH and water hardness also tend to reflect aspects of the wetlands substrate, soils and sediments or water source. The vegetation, surrounding land uses, light availability, position in the catchment and many other aspects also influence the water type.

Some wetlands have a naturally low dissolved oxygen content in the water, high levels of nutrients and a strong odour. This is due to natural processes occurring within the wetland, e.g. higher amounts of organic materiel may lead to a lower dissolved oxygen level, this is because decomposition requires oxygen and thus reduces the dissolved oxygen content of the water. High rates of decomposition can result in a decline in water quality and impair aquatic life. However decomposition in wetlands also binds excess nutrients, metals etc. to soil or can release some nutrients such as carbon and nitrogen into the atmosphere.[1]

Lake Numulla Photo by DES

Not all turbid waters are an indication of poor water quality. Some of our great inland rivers are naturally very turbid and the animals and plants that grow in them have adapted to these conditions. For management purposes it is important to know what the natural water type should be, e.g. trying to change land practises to change a naturally saline wetland would be an exercise in futility.

Natural variation between wetlands is common, a good example of this is Lake Numalla and Lake Wyara. Both lakes are on the western edge of the Murray-Darling Basin but each lake has its own catchment. Lake Numalla (almost 3000ha) is a freshwater lake while Lake Wyara (3800ha), less than 3km away, is saline. Lake Wyara fills entirely from its local catchment which has high salt levels. Find out more on the Currawinya National Park Nature, culture and history page.


  1. ^ Marjut, T & Gannon, R, Wetlands Functions (or Processes) and Values. [online], North Carolina State University. Available at: [Accessed 26 September 2012].
  2. ^ Sydney Water. Water facts. [online] Available at: [Accessed 1 March 2013].

Last updated: 29 January 2016

This page should be cited as:

Department of Environment and Science, Queensland (2016) Water type and quality, WetlandInfo website, accessed 13 April 2023. Available at:

Queensland Government
WetlandInfo   —   Department of Environment and Science