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Water chapter 4


4.2 River health

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Water

4.2 River health

The stresses on New South Wales inland rivers have eased after a period of protracted drought as widespread rains have led to high flows and enhanced the productivity of aquatic ecosystems. Coastal river systems have also experienced good flows that have enhanced the condition of riverine ecosystems and downstream estuaries.

The condition of macroinvertebrate communities in inland rivers is moderate, though this was recorded during low flows. Native fish populations remain in poor condition and have shown little response to higher flows. Nine out of 25 native fish species found in inland rivers were not sighted at all in recent surveys and exotic species accounted for 68% of the fish biomass sampled. Recruitment rates of native fish in coastal rivers were also very low. Large algal blooms that occurred in inland river systems during drought conditions in 2008–10 have since dissipated with increased river flows.

Most major inland river systems are still affected by pressures, including the ongoing impacts of water extraction and altered river flows, degradation of the riparian zone, catchment disturbance, invasion by exotic species and changes to water quality. As a result, most inland rivers remain in poor ecosystem health. By contrast, coastal rivers are less affected by flow regulation and, with the exception of fish communities, are generally in better ecological health.

The extent of use of water resources is a major determinant of the condition of freshwater riverine systems. Areas where the flow regime has changed the most (where river regulation and water use are highest) are generally showing the greatest signs of ecosystem stress.

Water sharing plans are being implemented for all major rivers in NSW to ensure a balance between human uses of water and the environment, with all plans for the Murray–Darling Basin to be completed by the end of 2013.

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NSW indicators

Indicator and status

Trend

Information availability

Health of aquatic macroinvertebrate communities

Stable

resonable

Health of fish assemblages

Decreasing

resonable

Hydrological condition

Increasing

resonable

SRA overall health index of Murray–Darling Basin rivers

Stable

resonable

Salinity levels

Stable

resonable

Phosphorus levels

Stable

resonable


Notes: Terms and symbols used above are defined in About SoE 2012 at the front of the report.


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Introduction

Healthy riverine ecosystems, comprising rivers and their riparian zones, floodplains and wetlands, are vital for the maintenance of aquatic and terrestrial biodiversity. However, while aquatic ecosystems have their own intrinsic value, healthy rivers are also critical to provide the ecosystem services necessary to maintain good water quality and supply, and enable opportunities for future economic growth. Rivers support a variety of beneficial uses of water by humans, including activities such as agriculture, aquaculture, fishing, recreation and tourism.

NSW has approximately 58,000 kilometres of rivers and major streams. These can generally be categorised as either short, high-gradient coastal streams or long, low-gradient inland rivers. The flow of these rivers is highly variable and often unpredictable. Streams and creeks may flow permanently or only intermittently after heavy rainfall and floods. About 97% of river length in NSW has been substantially modified (NLWRA 2002). Typical changes include the removal of riverine vegetation, the regulation of river flows, sedimentation from erosion of land and river banks, and the introduction of exotic species.

A river is in good health if it is resilient in the face of environmental change, including changes in climate patterns, resource exploitation and other human impacts. A primary objective is to achieve a long-term balance, whereby the integrity of natural systems is preserved while providing for a range of beneficial human uses. Factors that affect the resilience of river systems include river geomorphology, riparian vegetation, natural flow regimes, water quality and exotic species.

This section focuses on inland and coastal freshwater riverine ecosystems, including floodplains which are essential for connecting many types of freshwater wetlands and associated ecological processes to the rivers. Other ecosystem types are discussed elsewhere in this report: freshwater wetlands in Water 4.3 and estuaries in Water 4.6.

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Status and trends

The health of NSW coastal and inland rivers is likely to have improved following the breaking of a prolonged drought. In 2010, NSW had its third-wettest year on record and the wettest in over 50 years. It was also the wettest year on record for the Murray–Darling Basin (BoM 2011a). In 2010, a number of major flood events occurred in inland and coastal catchments across NSW, with significant flooding in southern NSW (BoM 2011a). Another wet year in 2011 caused further widespread flooding, particularly in northern NSW, and the flushing of most NSW river systems.

Most of the sampling of macroinvertebrates outlined in this report was, however, undertaken during drought conditions so any improvements as a result of the drought breaking will not be observed or reported until the next SoE report. For fish communities, some post-drought sampling has occurred in most valleys, excluding the Gwydir, Lachlan, Macquarie and Murrumbidgee rivers.

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River health

The Sustainable Rivers Audit (SRA) has developed a methodology to assess the health of rivers in the Murray–Darling Basin (MDB) based on indexes for hydrology, fish and macroinvertebrates. More recently, measures of riparian vegetation and physical form have been added. A set of rules is used to combine the indexes for fish, macroinvertebrates and riparian vegetation to determine an overall rating of ecosystem health (Davies et al. 2012). These are reported alongside index scores for hydrology and physical form, which provide additional information on some of the drivers of ecosystem health.

Overall results for the inland river systems of the Murray–Darling Basin are summarised in Table 4.5 and described in greater detail below. Data recorded for the three years up to the end of 2010 were available for the SRA analysis, collected mainly during drought conditions. No assessment has been conducted for those rivers in far western NSW beyond the MDB.

Table 4.5: Summary of ecosystem health and condition assessments for NSW Murray–Darling Basin rivers, 2010

Valley

Hydrology

Physical form

Fish

Macro-invertebrates

Riparian vegetation

Ecosystem health rating

Border Rivers

Good

Moderate

Moderate

Moderate

Poor

Poor

Condamine-Culgoa

Poor

Moderate

Moderate

Moderate

Good

Moderate

Warrego River

Good

Good

Poor

Good

Good

Moderate

Paroo River

Good

Good

Good

Good

Good

Good

Gwydir River

Poor

Moderate

Poor

Moderate

Moderate

Poor

Namoi River

Good

Moderate

Very poor

Moderate

Poor

Poor

Castlereagh River

Good

Good

Very poor

Moderate

Good

Poor

Macquarie–Bogan Rivers

Moderate

Moderate

Extremely poor

Moderate

Moderate

Very poor

Darling River

Moderate

Moderate

Poor

Poor

Good

Poor

Lachlan River

Moderate

Good

Extremely poor

Moderate

Poor

Very poor

Murrumbidgee River

Poor

Good

Extremely poor

Good

Moderate

Poor

Upper Murray River

Poor

Good

Extremely poor

Good

Moderate

Poor

Central Murray River

Poor

Moderate

Very poor

Poor

Good

Poor

Lower Murray River

Very poor

Moderate

Poor

Moderate

Poor

Poor

Source: Davies et al. 2012


Development of a complementary assessment process for coastal rivers in NSW has now commenced. Coastal rivers were assessed using similar, but not directly comparable methodologies, with an extra year of data recording available for the wet conditions of 2011. However, data for the condition of macroinvertebrates in coastal rivers was not available for this report. The results for the other indicators are summarised in Table 4.6.

Table 4.6: Summary of ecosystem health and condition assessments for NSW coastal rivers, 2011

Valley

Hydrology

Physical form

Fish

Riparian vegetation

Tweed River

Moderate

Very poor

Very poor

Poor

Brunswick River

Poor

Very poor

Poor

Poor

Richmond River

Poor

Poor

Poor

Moderate

Clarence River

Good

Moderate

Poor

Moderate

Bellinger River

Good

Moderate

Poor

Good

Macleay River

Good

Moderate

Poor

Poor

Hastings River

Moderate

Moderate

Very poor

Good

Manning River

Moderate

Moderate

Very poor

Good

Karuah River

Moderate

Moderate

Poor

Good

Hunter River

Moderate*

Very poor

Very poor

Moderate

Macquarie–Tuggerah Lakes

Poor

Moderate

Poor

Good

Hawkesbury–Nepean River

Good*

Poor

Very poor

Not assessed

Sydney Coast–Georges River

Not assessed

Poor

Very poor

Poor

Illawarra Coast

Not assessed

Moderate

Very poor

Good

Shoalhaven River

Good*

Moderate

Very poor

Moderate

Clyde River–Jervis Bay

Good

Good

Poor

Good

Moruya River

Good

Good

Very poor

Good

Tuross River

Good

Good

Very poor

Good

Bega River

Moderate

Moderate

Very poor

Moderate

Towamba River

Moderate

Moderate

Very poor

Good

Genoa River (NSW)

Not assessed

Good

Very poor

Good

Snowy River (NSW)

Good*

Poor

Extremely poor

Poor

Source: NSW Office of Water (NOW), NSW Office of Environment and Heritage and NSW Department of Primary Industries data 2012

Notes: Hydrological condition uses an assessment based on hydrological stress at low flows. Entries marked * do not have low-flow stress as they receive regulated flows which are greater than natural low-flow levels, so stress mainly occurs as extractions during high levels.
Fish condition uses the same methodology as the SRA with some minor adjustments. Fish results are very low due to a new measure for recruitment, which was found to be poor in coastal rivers. The measures for 'nativeness' and 'expectedness' gave relatively better ratings.


Hydrology

River flow influences virtually every facet of river ecosystem health and is therefore an indicator of river condition. The SRA hydrology condition index for inland NSW compares measured flows with reference conditions for each river using modelled data based on flow variability over the longer term (110 years of recording). The index reflects the overall effects of water resource development on historical flow patterns or the naturalness of the flow regime. However, the results are less indicative of shorter term variability or current flows, and therefore do not directly reflect the effects of either the recent drought or the subsequent flooding that has occurred in much of the Murray–Darling Basin over the past two years.

The SRA hydrology component has been broadened to assess most of the river network, not just individual locations within the regulated components and now includes:

  • improved hydrological modelling and broader assessment within valleys
  • the hydrological effects of farm dams and historical changes to land cover
  • measures of hydrological condition for both the channel and near and far floodplain environments (with four additional measures to characterise the overbank flooding regime)
  • assessments of temporal changes over the previous 12 years, alongside the condition assessment based on a longer term (30-year) record.

As a result of these changes, the condition scores for hydrology presented in Table 4.5 cannot be directly compared to those presented in SoE 2009 (DECCW 2009).

For coastal rivers, an approach consistent with that used to calculate hydrological stress for water sharing plans was used. This approach compares peak daily demand estimates with the 80th percentile flow to develop a low-flow hydrological index. It was adopted because the vast majority of licences issued for water extraction on the coast are for unregulated flows, which are generally accessed during dry conditions when river flows are low. The exceptions to this are those valleys with major storages for town water supply and river regulation, such as the Hunter, Hawkesbury–Nepean, Shoalhaven and Snowy rivers. In these valleys, dam releases are made to allow low flows to continue, but the dams capture most high-flow events.

Inland rivers: The SRA found that most sites in the Murray–Darling Basin were in moderate to good hydrological condition (Table 4.5). Those valleys that fell short of reference condition were the Condamine–Culgoa, Gwydir, Murrumbidgee and Upper, Central and Lower Murray valleys. For the Condamine, Gwydir, Murrumbidgee and Upper Murray valleys, the montane and upland zones were in good condition, with the poor rating resulting from changes to the hydrology of the main river channels. The Central and Lower Murray valleys are dominated by the regulation of the Murray River which was in very poor condition. The Border Rivers, Warrego, Paroo, Namoi and Castlereagh were rated as being in good hydrological condition (Davies et al. 2012).

Coastal rivers: The coastal rivers of NSW were mostly rated as being in good condition (Table 4.6). Only the condition of the Brunswick, Richmond and Macquarie–Tuggerah Lakes was rated as poor, reflecting the high peak demand during low flows in these rivers. The Tweed, Hastings, Manning, Karuah, Hunter, Bega and Towamba rivers had moderate levels of low-flow hydrological stress, reflecting a moderate impact at low flows as a result of extraction. All other valleys assessed were rated as good.

Physical form

The SRA's new physical form component has been developed and implemented since the first SRA report (MDBC 2008a). Assessment of physical form for the SRA uses remotely sensed data obtained from airborne laser altimetry (LiDAR) surveys, sediment data modelled by SedNet (a catchment-based sediment model) and empirical models of reference condition.

Inland rivers: Based on the SRA methodology, all inland rivers were rated as being in moderate or good physical form (Table 4.5). The Warrego, Paroo, Castlereagh, Lachlan, Murrumbidgee and Upper Murray valleys all received a good rating compared to reference. However, there are substantial areas of moderate and poor geomorphic condition in the Murray and Murrumbidgee catchments at the reach level.

A more elaborate system for assessing physical form is provided by the Riverstyles® framework, based on river type, condition and recovery potential (Brierley & Fryirs 2005). Riverstyles captures data at the river reach scale and therefore provides a more detailed analysis of geomorphic condition than the SRA in inland NSW. As a result, the outputs from Riverstyles mapping may be different from those derived using the physical form component of the SRA.

Riverstyles mapping also captures a stream's recovery potential, which is a measure of the capacity of a stream reach to return to a good or realistically rehabilitated condition, given the limiting factors of the reach. These factors are based on hydraulics and the ability of vegetation and sediment to facilitate geomorphic evolution (Outhet & Young 2004).

Mapping of geomorphic condition using the Riverstyles methodology has recently been completed for most of NSW and the outcomes are shown in Map 4.1. The results have been used to describe physical form for coastal rivers.

Map 4.1: Statewide geomorphic condition based on Riverstyles®

Map 4.1

Notes: Areas coloured off-white have not yet been assessed.


Coastal rivers: Most coastal valleys are in good to moderate condition with three – the Tweed, Brunswick and Hunter – having a condition score of very poor (Table 4.6). The Tweed and Brunswick both have large areas of coastal plains relative to the size of their catchments with significant scope for lateral channel movement across the floodplain. The likelihood for this to occur has increased following extensive changes to riparian vegetation and large woody debris which constrained this movement in the past. The Hunter River has also undergone major change since European settlement. On the south coast, the Clyde, Moruya, Tuross and Genoa rivers had ratings of good.

Fish

The fish component of the SRA has been broadened since the last report to include a measure for native fish recruitment. The recruitment indicator is weighted to have an intermediate influence on the overall fish condition score, relative to the existing 'expectedness' and 'nativeness' indicators. Data analysis also incorporates a more comprehensive quantification of native fish distributions in reference condition. As a result, the condition ratings for fish presented in this report are not directly comparable to those used in SoE 2009 (DECCW 2009).

Ratings of expectedness and nativeness showed a slight improvement since 2009 in both inland and coastal rivers so what appears to be a decline in overall condition is mainly due to the influence of the new indicator for fish recruitment.

Inland rivers: Overall, fish condition index scores indicate that condition was poor to extremely poor in most inland valleys (Table 4.5). Only the Paroo Valley received a rating of good while the Border Rivers and Condamine–Culgoa were rated moderate. The valleys in the worst overall condition were the Macquarie–Bogan, Lachlan, Murrumbidgee and Upper Murray.

'Expectedness' (an indicator of the proportion of species historically found in each valley that are still present) was good in the Border Rivers and moderate in the Gwydir and Darling valleys. In some valleys many native fish species expected to occur were not recorded at all. Of 25 native fish species inhabiting inland rivers, nine were not recorded at any site sampled, including four that are threatened: the flat-headed galaxias, Murray hardyhead, trout cod and southern pygmy perch. Native fish recruitment was rated good in the Condamine–Culgoa and Paroo valleys and moderate in the Border Rivers, Castlereagh and Lower Murray, and was worst in the Lachlan, Murrumbidgee, and Upper and Central Murray valleys.

While data available for the SRA river health analysis and the outcomes described in this report was sampled wholly during drought conditions, an extra year of unpublished data recorded during flood conditions in 2011 has since become available, but reveals little change to the overall results described here. Fish sampling was also undertaken in the far west of NSW, outside the Murray–Darling Basin. Results for Lake Bancannia were very poor and those for Cooper Creek, Lake Frome and the Bulloo River extremely poor.

Coastal rivers: Overall, fish condition index scores indicate that condition was poor to extremely poor in all coastal valleys with none rated as being in moderate or good condition (Table 4.6). Valleys in the best condition (poor) were the Brunswick, Richmond, Clarence, Bellinger, Macleay, Karuah, Macquarie–Tuggerah Lakes and Clyde River–Jervis Bay. The only coastal valley in extremely poor condition was the Snowy.

'Nativeness' of fish assemblages was generally very good, but this is the lowest weighted indicator for fish. Expectedness scores in coastal rivers were slightly better than for inland rivers, but much of the species diversity that should be present was not detected. Five freshwater species expected to be present in coastal catchments were not sampled at all during the reporting period, including the threatened Oxleyan pygmy perch and southern purple-spotted gudgeon, as well as jungle perch, spangled perch and the Darling River hardyhead.

Recruitment was lower in coastal valleys than in inland rivers with many of the species present not recruiting or recruits not being very abundant. The exact cause for this is not known but the impacts of fish barriers on the movement upstream of estuarine species and the recent spate of flooding in coastal catchments may be contributing factors.

Macroinvertebrates

The SRA macroinvertebrate index (MDBC 2003) describes the condition of macroinvertebrate communities in rivers. The index integrates indicators for observed macroinvertebrate families (compared with reference conditions) and sensitivity to disturbance. The macroinvertebrate component of SRA has been refined by improving the assessment of reference condition for macroinvertebrate communities and the calculation of indicator values. As a result, the condition ratings for macroinvertebrates presented in this report are not directly comparable to those reported in SoE 2009 (DECCW 2009).

Inland rivers: Overall, macroinvertebrate condition was best in the Warrego, Paroo, Murrumbidgee and Upper Murray systems which all had ratings of good (Table 4.5). This reflects relatively fewer stressors, such as water extraction or flow regulation, in these valleys. With the exception of the Darling and Central Murray valleys, which were in poor condition, all other valleys rated moderate.

Riparian vegetation

A new riparian vegetation index has been developed and implemented since the first SRA report (MDBC 2008a). Because no reference condition could be established for fringing riparian vegetation, scores for SRA analysis of inland rivers are based on the near-riparian zone, which describes vegetation occurring beyond the high river bank. For coastal rivers, riparian vegetation condition was assessed by analysing the extent of native woody vegetation that occurred within a 30-metre buffer applied to the stream line.

Inland rivers: For near-riparian vegetation, the Condamine–Culgoa, Warrego, Paroo, Castlereagh, Darling and Central Murray valleys had good condition ratings, while the Border Rivers, Namoi, Lachlan and Lower Murray valleys were in poor condition. The remaining valleys rated moderate.

Coastal rivers: Ratings of the condition of riparian vegetation for coastal rivers are closely related to physical form, with most valleys in moderate to good condition.

Ecosystem health

Map 4.2 shows the SRA ecosystem health ratings by river valley for the inland rivers of the Murray–Darling Basin only. The rating of river ecosystem health is a combined assessment based on the indexes for fish, macroinvertebrates and riparian vegetation shown in Table 4.5. Overall, the Paroo was the only river found to be in good ecosystem health, with the Condamine–Culgoa and Warrego rivers being in moderate health. Most other rivers received ecosystem health ratings of poor or very poor.

Due to the relatively recent commencement of broadscale coastal monitoring, it is not yet possible to make an overall assessment of ecosystem health for coastal rivers.

Map 4.2: SRA assessment of ecosystem health in the Murray–Darling Basin, 2010

Map 4.2

Notes: The SRA catchment ecosystem health rating is based on fish, macroinvertebrates and riparian vegetation.


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Threatened species

Declining biodiversity and the number of threatened species in Australia is of serious environmental concern. While it may be more widely recognised that many mammals, birds and other terrestrial species are threatened, some aquatic species are also under threat.

In NSW, seven of the 25 native freshwater fish species found in inland rivers and nine in total are listed as threatened with extinction under the Fisheries Management Act 1994. Three freshwater invertebrates have also been listed as endangered species under the Act and the status of many other species is of concern for conservation purposes.

Three aquatic ecological communities have been listed as endangered under the Act:

  • the Lowland Murray River ecological community
  • the Lowland Darling River ecological community
  • the Lowland Lachlan River ecological community.

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Water quality

Parameters for describing water quality include:

  • salinity, where the electrical conductivity (EC) of water is used as a surrogate measure for total concentration of all salts in water
  • nutrients, represented by total phosphorus and nitrogen content of the water, both measured in milligrams per litre (mg/L)
  • turbidity, where the light-scattering properties of water measured in nephelometric turbidity units (NTU) is a surrogate measure for the amount of suspended particles in water.

In NSW, the current water quality guidelines for ecosystem protection use the default trigger values in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC & ARMCANZ 2000) which were prepared under the National Water Quality Management Strategy (ANZECC & ARMCANZ 1994). The extent and frequency with which water quality monitoring data exceeds these trigger values provides an indication of the potential risk that environmental disturbance is occurring.

Salinity

Geology, climate, groundwater interactions and land-use practices all affect the level of salinity in NSW streams. High salt concentrations can degrade freshwater aquatic ecosystems while irrigation water with high salt loads can increase soil salinity.

Electrical conductivity is used as a measure of the level of salts in water. Continuous monitoring of electrical conductivity has been established at a number of sites across NSW. Table 4.7 shows mean daily salinity levels for a three-year period (2008–2011) and a 10-year period (2001–11). The table also shows the maximum salinity level measured during the latest three-year period of record at each stream measuring point. Mean daily salinity levels are well below the World Health Organization desirable upper limit for drinking water of 800 EC units. However the maximum spot readings in Table 4.7 indicate that the limits for drinking water have been exceeded in many systems for short periods.

Compared with the 10-year mean, the latest three-year reporting period shows a relatively stable or slightly lower mean daily electrical conductivity in the streams surveyed. Only the Hunter River at Greta showed a substantial increase (over 70 EC units) while five sites showed a decrease of the same magnitude or greater. This is likely to be due to major flooding that occurred in the latter part of 2010 and into 2011 as drought conditions broke across large areas of NSW.

Table 4.7: Electrical conductivity in selected NSW rivers

Stream measuring point

Daily river salinity levels (EC units) for specified period

Period of record

July 2001–June 2011 mean

July 2008–June 2011 mean

Maximum spot readings:
July 2008–June 2011

Macintyre at Holdfast

2002–2012

281.1

255.0

475.5

Mehi at Bronte*

2001–2012

436.0

331.2

167.8

Barwon–Darling at Collarenebri

2002–2012

283.7

214.6

330.7

Namoi at Goangara*

1995–2012

415.7

383.9

783.0

Namoi at Gunnedah

1995–2012

454.4

463.0

932.0

Castlereagh at Gungalman Bridge*

2001–2012

600.9

574.4

1,527.3

Macquarie at Carinda*

1999–2012

577.2

480.1

734.2

Macquarie at Baroona

1999–2012

450.1

425.5

1,057.9

Bogan at Gongolgon*

2000–2012

377.4

281.3

843.6

Hunter at Greta

1992–2012

713.5

784.9

1,447.0

Lachlan at Booligal*

1999–2012

593.6

520.7

858.8

Lachlan at Forbes

1999–2012

497.8

490.0

1,017.1

Murrumbidgee at Wagga Wagga

1993–2012

139.2

149.5

318.0

Murrumbidgee at Balranald*

1992–2012

149.1

158.3

329.0

Source: NOW data 2012

Notes: 'Maximum spot readings' (not means) cover the latest three-year period of record
* End-of-valley site


Nutrients

Nutrients, especially nitrogen and phosphorus, can have a significant effect on water quality when present in excess of ecosystem needs. The current guidelines for water quality (ANZECC & ARMCANZ 2000), along with NSW River Flow Objectives, provide default trigger values for water quality parameters designed to protect potential uses of water. Trigger values are conservative and where they are exceeded indicate the need to investigate possible causes, but they do not necessarily signify poor river health.

Map 4.3 shows the percentage of water samples from streams across NSW that had nitrogen and phosphorus concentrations above the ecosystem protection trigger values (ANZECC & ARMCANZ 2000). The results show that the northern inland and western drainages of NSW – the Border Rivers, Gwydir, Namoi, Macquarie, Darling and intersecting streams – regularly exceed trigger values for nutrients. In the central and southern inland drainages of NSW (the Lachlan and Murrumbidgee valleys), nitrogen and phosphorus levels are also elevated in mid-catchment locations, but trigger values are exceeded less frequently in the lower reaches of these drainages and in the Murray. In the coastal regions of NSW, trigger values are generally exceeded less frequently than in inland regions, with some exceptions around the Hunter Valley and north coast.

Map 4.3: Exceedences of ecological trigger levels for total nitrogen and total phosphorus, 2009–11

Map 4.3

Turbidity

Water clarity decreases – or becomes more turbid – as the amount of sediment and other particles in the water column increases. Turbidity levels vary according to the geology, soil type and cover, climate and intensity of disturbance to the landscape through land clearing and the erosion of agricultural land, stream banks and channels. High turbidity can decrease the amount of light that sustains plant growth, suppress the growth of aquatic organisms and choke habitat. It can also carry with it pesticides and other chemicals.

In NSW there is generally a pattern of low turbidity in upland areas and higher turbidity in lowland areas, reflecting the progression of rivers through the landscape and the effects of geology and topography. However there is also a tendency for higher levels of turbidity in river basins in the north-west of the state, such as the Paroo and Warrego, due to the naturally occurring dispersive soils found there.

Water quality by river valley

Nationally, an assessment of the water quality of river valleys (SKM 2011) was prepared for the Australian State of the Environment 2011 (ASoEC 2011). The NSW component of this assessment consisted of site and overall ratings for the inland river valleys of NSW, evaluated against the ANZECC default trigger values. The overall results for rivers are presented in Table 4.8.

Table 4.8: Water quality assessment for NSW river basins from the National Water Quality Assessment, 2007–11

River basin

Sites

Salinity

Total nitrogen

Total phosphorus

Turbidity

pH

Border Rivers

33

Fair

Very poor

Very poor

Fair

Fair

Moonie River

1

Good

Very poor

Very poor

Very poor

Good

Condamine–Culgoa Rivers

7

Good

Very poor

Very poor

Very poor

Good

Warrego River

1

Good

Very poor

Very poor

Very poor

Good

Paroo River

1

Good

Very poor

Very poor

Very poor

Good

Gwydir Lakes

24

Poor

Very poor

Very poor

Fair

Poor

Namoi River

38

Poor

Very poor

Very poor

Fair

Poor

Castlereagh River

1

Very poor

Poor

Very poor

Good

Good

Macquarie–Bogan Rivers

17

Poor

Very poor

Very poor

Good

Fair

Darling River

26

Fair

Very poor

Very poor

Poor

Poor

Lachlan River

15

Fair

Very poor

Poor

Fair

Good

Benanee River

4

Good

No data

No data

Good

Good

Murrumbidgee River

70

Good

Poor

Fair

Good

Good

Upper Murray River

16

Good

Poor

Poor

Good

Good

Murray-Riverina

20

Good

Good

Good

Good

Good

Lower Murray River

2

Good

Good

Good

Good

Good

Source: SKM 2011


The results show that the low-gradient, far western streams have a tendency to poor water quality, particularly turbidity but also nitrogen and phosphorus, with only the Mallee and Murray–Riverina recording good ratings. These results for water quality display some inconsistency with the outcomes of the SRA ecosystem health assessments shown in Table 4.5, most markedly for the Paroo River, but also the Warrego and Condamine–Culgoa. While these rivers have high levels of natural turbidity and therefore lower ratings for water quality, their ecosystems are adapted to these conditions and, being relatively undisturbed, they remain in better ecosystem health than the other rivers assessed.

These outcomes demonstrate the need for regional guidelines which better reflect natural variability in water quality and the influence of soil types and flow patterns on water quality at the regional level. Work is now progressing on the development of regional water quality guidelines for NSW. This involves modelling reference (natural) water quality and currently observed water quality, based on the characteristics of individual catchments and their levels of disturbance to develop more appropriate guidelines for water quality that are not uniform across the state.

Algal blooms

Most freshwater algal blooms in NSW are caused by blue-green algae (or 'cyanobacteria'), some of which produce toxins that are harmful to humans, livestock and aquatic fauna. However, non-toxic blooms can also have significant impacts on the health of aquatic ecosystems by depleting dissolved oxygen (which can cause fish kills), changing pH levels, reducing light penetration, and smothering habitat.

Drought conditions in 2008–09 and 2009–10 led to major blue-green algal blooms in many inland waters across NSW. In particular, warm conditions and low water availability caused major blooms in the Murray River in the autumns of both 2009 and 2010 that extended for over 1000 kilometres downstream of Lake Hume. In contrast, the 2010–11 period was much wetter with higher water levels and good flows in many NSW rivers and significantly fewer blooms reported.

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Pressures

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Water extraction and altered flow regimes

The drought in NSW, which lasted for over eight years in many river valleys, was replaced by wetter than average rainfall in 2010 and 2011. Water availability to the environment has improved in most inland rivers and wetlands following flooding events that have flushed river systems. However, natural flows continue to be modified by the effects of water extraction and flow regulation and control, through the dams built on most large river systems (see Water 4.1). Altered flow regimes also affect the seasonality and variability of flows, dampening both the peaks and troughs in water levels. This has an impact on the critical ecological processes that trigger breeding cues for bird and fish species, and has been a significant factor in the loss of biodiversity and decline of aquatic ecosystems over the longer term.

'Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands' has been listed as a Key Threatening Process (KTP) under the Threatened Species Conservation Act 1995. A related process, 'the installation and operation of in-stream structures and other mechanisms that alter natural flow regimes of rivers and streams' is also listed as a KTP under the Fisheries Management Act 1994. Alteration to natural flows has impacts on the habitat of native species, their dispersal and breeding, and encourages the establishment of introduced pest species.

The alteration to natural flow regimes encompasses a range of changes or disturbances within rivers and associated floodplains, including to the frequency, duration, magnitude, timing and variability of flow events, altered surface water levels and seasonality of flows, and changes to the rates at which water levels rise and fall. Water resource development, while necessary to provide resource security and access, is the main cause of alterations to natural flows through the building of dams and weirs, diversion or extraction of in-stream flows, and the alteration of flows on floodplains by levees and other structures.

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Drought

Australia is a land prone to drought and many of its native plants and animals, as well as most inland aquatic ecosystems, are adapted to drought conditions and recover quickly when rain falls and flows increase. Many species depend on the natural variability in river flows to complete critical stages in their life cycles. However prolonged drought is a major disturbance to riverine systems and can place severe stress on aquatic ecosystems.

Where the cumulative effects of drought conditions and water extraction continue over an extended period, critical thresholds in life cycles may be exceeded, placing prospects for recovery at risk. Due to long-term changes in river condition, many native fish populations are now much reduced in numbers and hence less resilient to change, such as the additional stress placed on them during the recent decade-long drought.

Following the end of the drought, several major rivers experienced new threats from 'blackwater events'. These occur after a dry spell when accumulated debris is washed into the river during a flood, lowering levels of dissolved oxygen as microbes in the water break down the organic matter. While blackwater events have occurred naturally in the past, changes to river hydrology have decreased their frequency but increased their intensity in lowland river floodplains. Blackwater events are now more likely to lead to complete oxygen starvation in rivers, resulting in more devastating fish kills and further ecosystem deterioration (Hardwick 2011).

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Floodplain fragmentation and harvesting

Floodplains are the areas of land that would naturally receive waters during floods, while floodplain harvesting is the collection, extraction, diversion or impoundment of water flowing across a floodplain. Historic settlement on floodplains has changed natural flow patterns and the behaviour of floods through associated structures, such as levee banks built to harvest water or protect property, as well as bridges, roads and railway lines. The redirection of floodwaters and reduction in flow levels have significant impacts on the health of riverine and wetland ecosystems.

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Catchment disturbance

Activities in river catchments can have a significant impact on riverine ecosystems, primarily through a reduction in water quality and changes to river geomorphology. Agriculture, urban stormwater and effluent can introduce nutrients, pollutants, suspended sediments and other contaminants into rivers and streams, reducing water quality during both high- and low-flow events. Changes in the land cover of catchments, such as the clearing of riparian and terrestrial vegetation and drainage of wetlands, have altered river geomorphology, including the widening of channels, headcut incisions in headwater streams, and increased sediment loads that smother aquatic habitats (Brierley & Fryirs 2005).

Pollution from a variety of sources has impacts on water quality and riverine ecosystem health. Point-source pollution has largely been addressed through regulatory processes, but pollution from diffuse sources is still an issue that affects water quality in some catchments (DECC 2009). The most significant pollutants from diffuse sources are sediments and nutrients, which are washed into streams by runoff from surrounding catchments. The quality and quantity of water pollution within a catchment largely depends on the extent of vegetation cover and local land management practices including agriculture and urban development. Generally, the more intensive the development, the greater the impact on riverine ecosystems.

Riparian vegetation provides habitat and food for aquatic communities so its disturbance is of particular significance for river health. Riverbank integrity is also critical because many species use overhanging banks and vegetation for habitat. Healthy fringing riparian vegetation is valuable for maintaining healthy aquatic ecosystems. It provides structural integrity for river banks to protect against erosion, as well as being a complex habitat and source of food and nutrients. The loss or degradation of the riparian zone through vegetation clearing and trampling by stock causes significant impacts.

Other forms of catchment disturbance that can influence river health include bushfires, roads, large dams and industrial activities such as mining.

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Water temperature

Cold water pollution is caused by low-temperature water being released into rivers from the bottom of large thermally stratified dams during summer. Cold water releases can prevent the natural seasonal changes in river temperature and reduce the range of temperature variation, both seasonally and diurnally, sometimes for hundreds of kilometres downstream. These variations may affect fragile ecosystems, fish breeding, the hatching of fish eggs and ecosystem productivity (Astles et al. 2004).

Discharge of cold water from dams is believed to be one of the main factors behind severe declines in native warm-water fish species in the Murray–Darling Basin (Phillips 2001). Nine dams in NSW are likely to cause severe cold water impacts: the Blowering, Burrendong, Burrinjuck, Copeton, Hume, Keepit, Khancoban, Pindari and Wyangala storages (Preece 2003). Over 3000 kilometres of NSW rivers are estimated to be affected by cold water pollution.

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Invasive species

Alien fish compete for food and space with native fish and frogs. They also prey on fish and frog eggs, tadpoles and juvenile fish, fundamentally altering food webs and habitats. Surveys of freshwater fish species by the NSW Department of Primary Industries (DPI) over the past three years found only 31% of the sites sampled were free from introduced fish, mainly in coastal rivers. A small number of sites – 6.7% – contained only introduced fish.

Averaged across all sites, introduced taxa accounted for 33% of the fish species collected at each site, 34% of the total fish abundance and 45% of the total fish biomass (DPI data 2011). The impact of introduced species is much greater in the inland rivers of the Murray–Darling Basin, with introduced fish present at 90% of all sites, and accounting for 40% of all species collected, 44% of total fish abundance and 68% of total fish biomass (see Biodiversity 5.4).

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Climate change

According to the findings of the CSIRO Sustainable Yields Assessment (CSIRO 2008a), the impacts of climate change on environmentally beneficial flooding in most regions of the Murray–Darling Basin, especially the highly developed regions, will be smaller than the impacts already brought about by water resource development. However, when the incremental impacts of climate change are superimposed on the existing pressures on water availability, the ecological consequences could be substantial as important ecological thresholds may be crossed (CSIRO 2008a).

Under a median climate change scenario, impacts by 2030 are expected to include:

  • extended dry periods between important flood events and reduced flood volumes for the 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 flood interval in the Lachlan River (CSIRO 2008c).

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Responses

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Established responses

NSW 2021

NSW 2021: A plan to make NSW number one (NSW Government 2011) is the Government's 10-year plan for NSW. Under Goal 22 – 'Protect our natural environment', the plan contains the following target: 'Improve the environmental health of wetlands and catchments through actively managing water for the environment by 2021'. This includes the strategic recovery and management of water for the environment to improve the health of the most stressed rivers and wetlands. Further details on Goal 22 are provided in Water 4.1.

Water sharing plans

Water sharing plans are a significant tool in water management for addressing river health in NSW, by improving the management of river flows and water extraction practices to protect a proportion of flows for the environment. They are described in greater detail in Water 4.1.

Water recovery

Improving the condition of aquatic ecosystems is a high priority for NSW. The Australian and NSW Governments have recovered water through the purchase of water entitlements and infrastructure works under a number of programs, including NSW RiverBank, The Living Murray program, Water for Rivers and the NSW Wetland Recovery Program. Further information on water recovery is available in Water 4.1.

The Living Murray program: This program is a major investment by the NSW, Victorian, South Australian, ACT and Commonwealth Governments to recover water and improve the environmental health of the Murray River at six significant ecological sites along the river. In NSW, these include the Millewa Forest, Koondrook–Perricoota Forest, Chowilla Floodplain, and the river channel itself.

The NSW target is to recover 249,000 megalitres (ML) of water for the environment. By June 2012, the program had recovered 221,000 ML of water.

Projects completed in NSW include:

  • the Great Darling Anabranch Pipeline scheme, which saw the removal or modification of water regulation structures that previously created a series of pools, and replacing them with pumps, a pipeline and a filtration system to restore more natural flows to the Great Darling Anabranch, saving 47,000 ML of water per year
  • the purchase of 12,000 ML of irrigation entitlement from the Poon Boon Irrigation Trust
  • wetland rehabilitation works on the Edward River through construction of 18 regulators to stop the unwanted flooding of the Millewa Forest, saving 7100 ML of water a year
  • construction of a regulator to better manage flows and prevent unnatural flooding of Croppers Lagoon, providing an annual saving 8000 ML of water.

NSW Rivers Environmental Restoration Program: This program was completed in 2011. It targeted important wetlands in the Macquarie Marshes and the Gwydir, Lachlan and Murrumbidgee river systems to arrest their decline by purchasing water for the environment and improving the management and delivery of environmental flows. The achievements of this program are described in greater detail in Water 4.3.

NSW Weir Review

The 2006 Weir Review identified more than 3300 dams and weirs on NSW rivers. A central issue for water sharing plans is the degree to which any management recommendation to remove or modify weirs affects water resource availability and water sharing arrangements. While weirs create impediments to fish passage and cause impacts on water quality, they can provide valuable 'compensatory' refuge areas for fauna during drought times. These factors need to be carefully weighed when considering management intervention.

Rural floodplain management plans

Rural floodplain management plans have been adopted for 17 floodplains covering approximately 20,800 square kilometres. Completion of another four plans currently being developed will bring the total coverage to more than 24,300 square kilometres. Plans have been adopted or are being prepared for floodplains associated with rural sections of the Namoi, Gwydir, Macquarie, Lachlan, Murrumbidgee and Murray rivers and the Liverpool Plains.

The objective of the plans is to enhance the health of flood-dependent ecosystems by increasing floodplain connectivity while also managing the risk from flooding through control of development that is likely to block or redistribute flows during floods. This is achieved by mapping floodway networks based on historical flood information to allow for the unimpeded passage of floodwaters. Floodplain management plans are statutory plans under the Water Act 1912 and Water Management Act 2000 and form the basis for assessing floodplain work approvals.

Water releases for the Snowy River

Water for Rivers was established to achieve significant improvements in environmental flows into the Snowy and Murray river systems. Targets include returning 212,000 ML or 21% of average annual natural flows to the Snowy River and 70,000 ML to the Murray River in a staged approach over 10 years. In the 2010–11 water year, a total of 24,200 ML of water was committed for additional environmental flows by the NSW, Victorian and Commonwealth Governments. The first release of 16,600 ML occurred in 2010 and was the largest environmental release to the Snowy River since the Jindabyne Dam was built in 1967. This was followed by an additional 7600 ML in April 2011 and 84,000 ML during October 2011.

Pipeline NSW

Under Pipeline NSW, old and wasteful open channels that deliver stock and domestic water from NSW rivers are being replaced with piped systems modelled on the successful Cap and Pipe the Bores program in the Great Artesian Basin. New pipelines will pump water from rivers or groundwater sources and deliver it directly to farm storage tanks and stock troughs via a network of underground pipes in three locations:

  • the Barwon Channel Association stock and domestic pipeline, saving 1488 ML per year
  • the Lower Gwydir domestic pipeline, saving 2544 ML per year
  • the Lower Lachlan Noonamah Water Authority stock and domestic pipeline, saving 795 ML per year.

The water saved by Pipeline NSW will be reallocated and managed through environmental water licences held by the NSW and Commonwealth Governments to benefit the rivers.

NSW Diffuse Source Water Pollution Strategy

Pollution from diffuse sources accounts for the majority of pollutant loads in the state's waterways. The objective of this strategy (DECC 2009) is to reduce diffuse source water pollution in all NSW surface and groundwaters. The strategy's primary focus is on sources of priority pollutants that are not currently regulated. The three main pollutants to be addressed are sediments, nutrients and pathogens, which can arise from a multitude of sources, including agricultural land uses, sealed and unsealed roads, and urban stormwater.

Cold Water Pollution Strategy

The Cold Water Pollution Strategy adopted in 2004 aims to reduce the significant effect that major dams have on the ecology of many of the large rivers across NSW. The strategy is being implemented in five-year stages: outcomes achieved in the first stage included major infrastructure works at Jindabyne and Tallowa Dam, investigations at Keepit and Burrendong dams, integration of cold water pollution conditions in State Water works approvals and identification of high priority dams for possible action in Stage 2. Guidelines for Managing Cold Water Releases became available in April 2011 (NOW 2011) and a Report on the implementation of Stage 1 of the strategy was released in July (NOW 2012).

Native Fish Strategy for the Murray–Darling Basin 2003–2013

The Native Fish Strategy for the Murray–Darling Basin 2003–2013 (MDBMC 2003) has the long-term goal of rehabilitating native fish communities back to 60% of estimated pre-European fish populations by the year 2050 (MDBC 2006). It covers a range of initiatives designed to reduce the threats to native fish and engage the local community in improving river health across the basin. Actions taken so far have included placement of over 5100 snags in rivers and improving the condition of over 90 km of riparian vegetation. In addition, over 14,800 people across the state have attended community engagement events promoting activities and an understanding of native fish issues.

Fishways

Remediation of fish passage at weirs, dams and road crossings by constructing fishways or fish ladders and redesigning existing barriers plays an important role in improving the health of fish communities. Improvements have been delivered through three major projects. The Sea to Hume Dam Fishway Program involves the construction of 19 fishways on the Murray and adjacent waterways, improving fish access to over 2000 km of waterway. The program is nearing completion, with 14 fishways now completed.

The Fish Superhighways Program is a strategic initiative to improve fish passage at State Water Corporation assets across NSW. Fishways have been completed at 15 weirs, allowing improved passage to over 1700 km of river, while a further 17 fishways in the planning and design phase will improve connectivity to another 1600 km. Six weirs have been removed since 2002 and the removal of another 18 is being investigated.

The Bringing Back the Fish Project concluded in 2009, improving migratory fish access to over 1200 km of waterways in coastal NSW.

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Developing responses

Water shepherding project

The NSW and Commonwealth Governments signed a Memorandum of Understanding (MoU) on shepherding environmental water in July 2010. The MoU sets out the principles for how water purchased for environmental purposes in one location will be protected from extraction or 'shepherded' to a downstream location. Submissions on proposed arrangements for shepherding environmental water in NSW were received until July 2012.

Draft Floodplain Harvesting Policy

A draft NSW Floodplain Harvesting Policy (NOW 2010) to provide a framework for managing licensing and approvals for the harvesting of water from floodplains has been released for public consultation. More detail is available in Water 4.1.

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Future opportunities

The monitoring of habitat and ecosystem responses to environmental flows will allow knowledge to be refined so that adaptive management can optimise the benefits of flows and better target high-value ecosystems.

Many native fish species have been under severe stress during the extensive drought that broke in 2010. The recovery of species as more typical flow patterns resume will be monitored and supplementary measures, such as selective restocking considered, where appropriate.

While point sources of water pollution are generally well-managed, there is still scope to improve the management of diffuse-source pollution, primarily 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.

Further research is desirable to determine the likely effects on the health of aquatic ecosystems of changes in water availability and possible shifts in community composition due to the altered seasonality of flows.

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Contents SoE 2012 View printable page Last modified: December 2012