River Health

Graphic of trees, hill and river

River Condition Index


out of 40 NSW river valleys have a 'moderate' or better rating

Graphic of three fish in water

Fish communities


of NSW river valleys are rated 'poor' or worse

The overall condition of rivers across NSW is moderate. Aquatic ecosystems in the major rivers of the Murray-Darling Basin are generally in poorer condition than those in coastal rivers.

The major inland river systems are affected by the ongoing impacts of water extraction, altered river flows, and catchment changes such as vegetation clearing. Generally, the greatest signs of ecosystem stress occur where flow regimes have changed most.

Most coastal rivers are less affected than inland rivers by water extraction and flow regulation. With the exception of their fish communities, coastal rivers are generally in better ecological health.

Fish communities are in poor condition across the state but are improving within the Murray-Darling Basin. The widespread distribution of introduced carp in the Murray-Darling Basin has had a significant impact on the health of fish communities.

Exceedances of water quality standards for the nutrients phosphorus and nitrogen increased slightly during the period 2015–17. The increase is mainly due to the effects of flooding in some inland catchments in 2016. Salinity is relatively stable in most streams surveyed.

Water management initiatives aim to balance human uses of water with environmental water, to maximise the outcomes for river and wetland health. Fifty-eight water sharing plans have been finalised for all water sources in NSW.

In the Murray-Darling Basin, these plans will underpin the development of nine surface water resource plans by 2019, which will detail rules for planned environmental water and 11 groundwater plans.

Related topics: Threatened Species | Invasive Species | Water Resources

NSW Indicators

* You may need to scroll to the right to see the full content, or switch to landscape orientation.

Indicator and status Environmental 
River condition index for NSW rivers
Stable  ✔ 
Health of fish assemblages
Getting better  ✔✔  
Stable ✔✔
Nitrogen and phosphorus levels
Stable  ✔✔ 


Terms and symbols used above are defined in How to use this report.


NSW has approximately 58,000 kilometres (km) of rivers and major streams. They can be categorised as:

  • short, high-gradient coastal streams
  • long, low-gradient inland rivers.  

About 97% of river length in NSW has been substantially modified (NLWRA 2002). Yet healthy river ecosystems, comprising rivers, their riparian zones, floodplains and wetlands, are vital to aquatic and terrestrial biodiversity.

Healthy rivers are also critical for the ecosystem services needed to maintain good water quality and supply. Rivers are vital to support economic growth and enable human activities, including agriculture, aquaculture, fishing, recreation and tourism.

Rivers and aquatic ecosystems are under pressure from:

  • regulation of river flows
  • extraction of water from rivers
  • clearing of riverside vegetation
  • diffuse source water pollution, including agricultural runoff and urban stormwater
  • sedimentation from runoff and the erosion of land and river banks
  • introduction and expansion of exotic species.

A primary objective of river management is to achieve a long-term balance: preserve the integrity of natural systems but also provide for a range of beneficial human uses.


Natural river flows have been modified by:

  • water extraction
  • dams and other structures.

Water flows in inland NSW and in coastal river systems supplying major metropolitan areas are particularly affected by dams and other structures (see Water Resources topic). Changes to natural river flows, and dampening of their peaks and troughs, affect the critical ecological processes that trigger breeding in birds and fish. These altered flow regimes in rivers are a significant cause of long-term decline in aquatic ecosystems.

River flow regimes also play an important role in creating and maintaining the physical habitat of river channels.

Many Australian native fish species must access suitable habitat to complete their lifecycles. The Fisheries Management Act lists 'installation and operation of instream structures and other mechanisms that alter natural flow regimes and streams' as a key threatening process. These structures:

  • disrupt migration of native fish populations
  • exclude these fish from large areas of vital breeding and spawning habitat
  • restrict their access to food
  • limit available shelter for fish, leading to increased predation
  • reduce fish population's genetic variability.

A database of all known fish barriers in NSW, compiled by Fisheries NSW, identifies more than 10,000 structures, nearly 5,000 of which are barriers to fish. Among them are more than 2,000  dams, weirs and regulators, the most common type of major barrier. A further 1,800 road crossings and 480 floodgates also impede fish passage (NSW Fish Habitat Partnership 2017).

Each year irrigators divert a large portion of river water using canals and pumps. Many adult fish are caught in irrigation canals or pumps. If pumping occurs when fish are spawning, this also destroys their eggs and larvae. On the Namoi River some pumping stations remove more than 200 fish daily (Baumgartner et al. 2009). NSW's western-flowing rivers have more than 4,546 pumps greater than 200 millimetres (mm) in size.

In the Murray-Darling Basin, more than 80% of main channel weirs use an undershot (gated) design (Boys et al. 2014) to control water flows. Where undershot weirs are used, fluid shear stress is a common problem that can injure or kill fish. Many fish eggs and larvae die when passing through undershot weirs due to the distortion encountered. Small-scale experiments with golden perch demonstrate high susceptibility to fluid shear stress, with egg mortality rates exceeding 90% (Boys et al. 2014; Baumgartner et al. 2006).

When operators discharge water from the bottom of dams, this injects colder water into sensitive downstream ecosystems. This cold water release alters rivers' thermal regimes, sometimes for hundreds of kilometres downstream. Cold water pollution (CWP) affects a range of physiological and biological processes in native fish species, including feeding, spawning, hatching and larval development (Lugg & Copeland 2014).

Nine inland NSW dams cause relatively large and pervasive CWP:

  • Blowering
  • Burrendong
  • Burrinjuck
  • Copeton
  • Hume
  • Keepit
  • Khancoban
  • Pindari.

CWP is also a medium pressure downstream from some dams supplying major coastal metropolitan areas, including below upper Nepean catchment dams, Warragamba Dam and Tallowa Dam on the Shoalhaven River.

In some cases, discharges from dams cause downstream temperatures to drop more than 15°C below natural summer conditions (Hardwick et al. 2012).

Runoff causing water pollution is affected by:

  • the extent of vegetation cover in a river catchment
  • local land use and land management practices, such as agriculture and urban development.

Runoff may increase nutrients and sediments in the river or stream. It may even modify the geomorphology of the river. Clearing riparian and land plants and draining wetlands also affect river geomorphology by:

  • widening river channels
  • leading to head cut incisions in headwater streams
  • increasing sediment loads, smothering aquatic habitats (Brierley & Fryirs 2005).

Generally, the more intensive a development, the greater its impact on river ecosystems.

Healthy riparian vegetation is important to maintain healthy aquatic ecosystems. The structure it provides protects riverbanks from erosion and creates complex habitat and sources of food and nutrients, including for aquatic communities. Intact riverbanks are also critical because many species use overhanging banks and their vegetation for habitat.

River health is affected when riparian vegetation is disturbed. Clearing and trampling by livestock destroys or degrades riparian zone vegetation, with significant impacts.

Other forms of disturbance that influence river health include:

  • bushfires
  • roads
  • large dams
  • industrial activities such as mining.

Introduced pest fish can compete with native species. They prey on fish and frog eggs, tadpoles and juvenile fish, and fundamentally alter food webs and habitats. Freshwater fish surveys over the past three years found:

  • only 13% of all sites sampled were free from introduced fish, mainly in coastal rivers
  • 4% of sites contained only introduced fish
  • introduced fish taxa accounted for 36% of fish species collected at each site, 37% of total fish abundance, and 58% of total fish biomass, averaged across all sites.

Allowing for the greater proportion of sampling in the Murray-Darling Basin during the latest surveys, these numbers show an improvement compared to results reported in SoE 2015.

No new introduced fish species became established in NSW's freshwater aquatic habitats during the period 2014–2017. See the Invasive Species topic.

The Australian landscape is adapted to natural drought conditions; many species have lifecycles that rely on natural variability in river flows. Prolonged drought, however, causes major disturbance to river systems and can severely stress aquatic ecosystems.

Where the combined effects of drought conditions and water extraction build up over extended periods, they may exceed critical thresholds for life cycles of species. This stress threatens the recovery of at-risk fish populations. Where long-term changes to river conditions have reduced native fish populations, they are less resilient to further change, such as those imposed by the decade-long Millennium Drought of the 2000s.

Climate change is likely to gradually add to existing stressors, particularly water availability pressures and the impacts of altered river flows.

Climate change will affect environmentally beneficial flooding that occurs in most Murray-Darling Basin regions (especially highly-developed regions). However, these climate change effects will be smaller than existing impacts from water resource development, according to the CSIRO Sustainable Yields Assessment (CSIRO 2008a).

Nevertheless, when climate change impacts are superimposed on existing water availability pressures, important ecological thresholds may be crossed. The ecological consequences may be substantial (CSIRO 2008a). By 2030, under a median climate change scenario, expected impacts include:

  • extended dry periods between important flood events and reduced flood volumes for Murray icon sites identified in The Living Murray program (CSIRO 2008a)
  • a 10% increase in the interval between beneficial flood events in the Macquarie River (CSIRO 2008b)
  • a 24% increase in the interval between floods in the Lachlan River (CSIRO 2008c).


NSW Diffuse Source Water Pollution Strategy

Pollution from diffuse sources accounts for most pollution in NSW waterways. The NSW Diffuse Source Water Pollution Strategy (DECC 2009) aims to reduce this pollution in all NSW surface and groundwater, by focusing on sources not currently regulated. It addresses three main pollutants: sediments, nutrients and pathogens. These pollutants come from many sources, including agriculture, sealed and unsealed roads, and urban stormwater.

There is an action in the Marine Estate Management Strategy (MEMA 2018) to clarify NSW Government and local government roles and responsibilities for diffuse source water pollution.

Fish habitat policy and guidelines

Policy and guidelines updated in 2013 aim to maintain and enhance fish habitat in NSW to benefit native fish (including threatened species) in marine, estuarine and freshwater environments (DPI 2013).

Floodplain management plans (Water Management Act 2000)

Floodplain management plans, prepared under the Water Management Act 2000, will help implement the NSW Healthy Floodplains Project. These plans provide a whole-of-valley framework to assess and determine flood work applications.

The Department of Industry Water, in partnership with the Office of Environment and Heritage, is preparing six floodplain management plans for:

  • the Gwydir
  • Barwon-Darling
  • Upper Namoi
  • Lower Namoi
  • Border Rivers
  • Macquarie valley.

These whole-of-valley plans will supersede 20 localised floodplain management plans already in force for areas of these six floodplains. The plans to be superseded were prepared under the Water Act 1912 and the Water Management Act 2000.

As statutory plans, the new whole-of-valley plans must address risks to life and property from flooding. Some features of floodplains with ecological and cultural significance depend on flooding; the plans must also provide connectivity to and from these flood-dependent assets.

Water sharing plans

Water sharing plans are important tools to address river health in NSW. They provide for better management of river flows and water extraction practices and protect a proportion of all flows for the environment. Water sharing plans developed for all NSW water sources were in place by the end of 2018. The plans are reviewed every 10 years, at which time they are either remade or renewed.

Under the Murray-Darling Basin Plan, water sharing plans in the basin will underpin 20 water resource plans (WRPs) to be developed by 2019. See Water Resources topic.

Water resource plans

The NSW Government will develop water resource plans as part of implementing the Murray-Darling Basin Plan. The Basin Plan provides a framework to integrate the basin's water resource management over the long term. Water resource plans will align basin-wide and state-based water resource management. They will recognise and build on existing water planning processes.

Each water resource plan will have:

  • the relevant state water sharing plan
  • a long-term environmental water plan
  • a risk assessment
  • a water quality management plan
  • an incident response guide to deal with periods of drought and poor water quality.

See Water Resources topic.

Water quality management plans

Under the Murray-Darling Basin Plan, water quality management plans must be developed for all basin areas with water resource plans.

Each water quality management plan will:

  • establish water quality objectives and targets for freshwater-dependent ecosystems, irrigation water, and recreational uses
  • identify key causes of water quality degradation
  • assess risks from water quality degradation
  • identify measures that help achieve water quality objectives.

Environmental water holdings

In NSW, water has been purchased or recovered for the environment through a number of water recovery programs funded by the Commonwealth and NSW governments. The cumulative total for all this licensed environmental water for regulated rivers in NSW is about 2,412,000 megalitres (ML), and about 70,000ML in unregulated rivers (see Water Resources topic).

NSW and Australian government agencies work together to release and manage environmental water holdings. They manage environmental water through two types of plans:

  • Annual environmental watering plans outline priorities for environmental water use in the coming year, considering climatic factors and water availability.
  • Environmental water management plans are strategic plans for wetlands. They link environmental water management with activities of other government agencies. These plans identify environmental assets and values, assess water-use priorities, and outline the water and land management issues that must be addressed to support environmental values.

Environmental flows are also provided by releases from dams on coastal river systems that provide urban water supply for major metropolitan areas.  The NSW Government has committed to new variable environmental flows from Warragamba Dam by 2024 that will reintroduce more natural downstream flow conditions and improved water quality (Metropolitan Water 2017).


Fishways and remediation work in NSW have re-opened thousands of kilometres of river habitat to fish. Remediation includes replacing low-level road crossings and causeways with larger fish-friendly box culverts. These culverts allow fish to pass, but also improve access for landholders during floods. Recent works include fishways completed at Kyogle and South Dubbo Weir.

The WaterNSW 2017 Fishways Strategy for 46 priority fishway sites is part of a broader strategy to address the state's 90 highest-priority barriers to fish passage (WaterNSW 2018). With funding and implementation, the strategy could open up about 8,200 km of rivers and streams to migrating fish.

Continued monitoring will shed light on how habitats and ecosystems respond to environmental flows. This information will refine knowledge and guide adaptive management, to better target high-value ecosystems and enhance the benefits of these environmental flows.

Point sources of water pollution are generally well managed. However, scope exists to better manage diffuse-source pollution, mainly from agricultural runoff and urban stormwater. Stormwater harvesting developments, runoff controls, and initiatives to promote revegetation and better land management practices in catchments are being implemented to improve water quality. This includes initiatives being funded under the NSW Government’s $112 million Catchment Action NSW initiative (LLS 2017).


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