Menindee fish deaths follow up: Darling-Barka River water tests

The NSW Environment Protection Authority (EPA) collected three water samples on 24 April 2023 at Menindee along the Darling-Barka River.

Samples were checked for pesticides, excess nitrogen and phosphorus, ammonia, metals, bacteria, algae and algal toxins.

Sample locations

Water was sampled on 24 April 2023 from three locations on the Darling-Barka River at Menindee.

• Sample 1 – approximately 840m NE of Menindee Golf Club
• Sample 2 – end of Maiden St
• Sample 3 – beneath Menindee St bridge

More sampling

The EPA is conducting regular water quality monitoring on the Darling-Barka River from upstream of Menindee to Pooncarie as well as the Great Darling Anabranch. The test results from these samples will also be published on this website.

In-field measurements

At the time of sampling, the EPA collected in-field measurements for pH, dissolved oxygen, conductivity, temperature and turbidity.

All parameters are within the expected ranges.

Nitrogen, phosphorus and ammonia

Sample results show that total nitrogen and total phosphorous are higher than the acceptable levels given for lowland river ecosystems in NSW (ANZG 2018, which are in agreement with the regionally specific set of guideline values for the Murray-Darling outlined in the Basin Plan 2012). Total nitrogen was detected at three times higher than the guideline value while total phosphorous was detected at four times higher.  Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. Ammonia was well below the Australian and New Zealand water quality guidelines for toxicity. While the levels would not be expected to be harmful to fish, the ammonia could promote growth in algae and macrophytes. The ammonia is likely to be from river sources including rotting fish and flood organic matter rather than diffuse inputs from surrounding land.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in all samples for a range of algal species, including blue-green algae. The algal toxin Cylindrospermopsin was detected in all samples.

The algae levels detected fall within the ‘amber’ alert levels. An ‘amber alert’ is in place in the Darling Barka River at Menindee as of 10 May 2023.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples from all three locations. All samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per the National Health and Medical Research Council (NHMRC) recreational and Australian and New Zealand Water Quality (ANZG) guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10 x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia.

References

ANZG (2018), Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia. Available at www.waterquality.gov.au/anz-guidelines

Basin Plan (2012), Schedule 11, Water Act 2007, Murray-Darling Basin Authority, Commonwealth of Australia

NHMRC (2008), Guidelines for managing risks in recreational waters, Australian Government National Health and Medical Research Council

NSW Department of Primary Industries (DPI) Fisheries collected 5 samples of golden perch (Macquaria ambigua) from the Darling-Barka River at Pooncarie on 28 March.

The gastrointestinal tract and gills of the fish were analysed for metals and pesticides. The gastrointestinal tract can show what chemicals have been ingested by the fish and the gills give an indication of overall exposure from the surrounding water.

Pesticides

Samples were scanned for more than 600 pesticides. None were detected.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment.

The only metals found in the gastrointestinal tract of the fish were zinc and mercury. These metals are known to bioaccumulate in fish. No gastrointestinal tract data are available as background in NSW, but these concentrations are below concentrations reported internationally.

Zinc and mercury were also found in the gills of the fish. This indicates some recent exposure to these metals from the water. However, water concentrations were all below water quality guidelines indicating these metals will not have adversely impacted the health of the fish.

¹Regine 2006     ² Luczynska 2016     ³ Rajkowska 2013

Download the full test reports: 28 March

The full report (with individual's names and addresses redacted for privacy) are available for download

• Report for metals and pesticides - 28 March, Pooncarie fish samples (PDF 1.5MB)

Sample locations

Fish samples were collected from two locations near Pooncarie on 28 March 2023.

• Sample 1 – Downstream of Pooncarie Weir
• Sample 2 – Pooncarie Cafe
  
  

References

FSANZ. 2001. Generally expected levels (GELs) for Metal Contaminants - Additional guidelines to maximum levels in Standard 1.4..1 - Contaminants and Natural Toxicants. Australian New Zealand Food Standards Code.

¹Regine M.B., Gilles D., Yannick D. and Alain B. (2006). Mercury distribution in fish organs and food regimes: Significant relationships from twelve species collected in French Guiana (Amazonian basin). Science of the Total Environment. 368: 262-270

²Luczynska J., Luczynski M. J. and Paszczyk B. (2016). Assessment of mercury in muscles, liver and gills of marine and freshwater fish. Journal of Elementology. 21(1): 113-129

³Rajkowska M. and Protasowicki M. (2013). Distribution of metals (Fe, Mn, Zn, Cu) in fish tissues in two lakes of different trophy in Northwestern Poland. Environmental Monitoring and Assessment. 185(4): 3493-3502

WaterNSW collected six water samples for the EPA on 11 April 2023 downstream of Menindee on the Darling-Barka River,  the Murray River and the Great Darling Anabranch.

Samples were checked for pesticides, excess nitrogen and phosphorus, ammonia, metals, bacteria, algae and algal toxins.

Sample locations

Water was sampled on 11 April 2023 from six locations downstream of Menindee on the Darling-Barka River, the Murray River and the Great Darling Anabranch:

• Sample 1 – Murray River at Merbein Pump Station
• Sample 2 – Darling-Barka River at Tapio
• Sample 3 – Darling-Barka River at Ellerslie
• Sample 4 – Darling-Barka River at Burtundy
• Sample 5 – Great Darling Anabranch at Silver City Highway
• Sample 6 – Murray River at Fort Courage

More sampling

The EPA is conducting regular water quality monitoring on the Darling-Barka River from upstream of Menindee to Pooncarie as well as the Great Darling Anabranch. The test results from these samples will also be published on this website.

In-field measurements

At the time of sampling, WaterNSW collected in-field measurements for pH, dissolved oxygen, conductivity, temperature and turbidity.

Dissolved oxygen ranged from 5.6mg/L to 10.3mg/L at the six locations. Native fish and other large aquatic organisms require at least 2mg/L of dissolved oxygen to survive but may begin to suffer if levels are below 4 to 5mg/L for prolonged periods.

pH was outside the guideline value in the Murray River at Merbein Pump Station and Fort Courage, and in the Great Darling Anabranch at Silver City Highway. 

All other parameters are within the expected ranges.

Nitrogen, phosphorus and ammonia

Sample results show that total nitrogen and total phosphorous are higher than the acceptable levels given for lowland river ecosystems in NSW (ANZG 2018, which are in agreement with the regionally specific set of guideline values for the Murray-Darling outlined in the Basin Plan 2012). Total nitrogen was detected at five times higher than the guideline value while total phosphorous was detected at ten times higher. Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. The water samples from 11 April show high levels of nitrite and nitrate, and there is a potential for further harm to aquatic organisms.

Ammonia was well below the Australian and New Zealand water quality guidelines for toxicity and as a stressor (i.e. nutrient).  The levels would not be expected to be harmful to fish or promote growth in algae and aquatic plants.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in all samples for a range of algal species, including blue-green algae. The algal toxin Cylindrospermopsin was detected in the samples collected from the Murray River at Fort Courage and the Great Darling Anabranch at Silver City Highway.

The algae levels detected fall within the ‘amber’ to ‘red’ alert levels. A ‘red alert’ is in place in the Murray River at Fort Courage and in the Great Darling Anabranch at Silver City Highway as of 28 April 2023. An  ‘amber alert’ is in place in the Murray River at Merbein and in the Darling Barka River at Merbein, Ellerslie and Burtundy.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples from all six locations. All samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per the National Health and Medical Research Council (NHMRC) recreational and Australian and New Zealand Water Quality (ANZG) guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10 x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia.

References

ANZG (2018), Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia. Available at www.waterquality.gov.au/anz-guidelines.

Basin Plan (2012), Schedule 11, Water Act 2007, Murray-Darling Basin Authority, Commonwealth of Australia.

NHMRC (2008), Guidelines for managing risks in recreational waters, Australian Government National Health and Medical Research Council.

The EPA collected two water samples on 4 April 2023 downstream of Menindee at Pooncarie.

Samples were checked for pesticides, excess nitrogen and phosphorus, ammonia, metals, bacteria, algae and algal toxins.

Sample locations

Water was sampled on 4 April from two locations on the Darling-Barka River at Pooncarie:

• Sample 1 – Karoola Reach, approximately 60 kilometres north of Pooncarie
• Sample 2 – Pooncarie Bilbarka Park

More sampling

WaterNSW has collected more water samples for the EPA from the Darling-Barka River on 11 April 2023. The test results for these samples will also be published on the EPA webpage.

In-field measurements

At the time of sampling, the EPA collected in-field measurements for pH, dissolved oxygen, conductivity, temperature and turbidity.

Dissolved oxygen at Site 1 was 2.53mg/L and at Site 2 was 3.11mg/L. Native fish and other large aquatic organisms require at least 2mg/L of dissolved oxygen to survive but may begin to suffer if levels are below 4 to 5mg/L for prolonged periods.

All other parameters were within the expected ranges.

Nitrogen and phosphorus

Sample results show that total nitrogen and total phosphorous are higher than the acceptable levels given for lowland river ecosystems in NSW (ANZG 2018, which are in agreement with the regionally specific set of guideline values for the Murray-Darling outlined in the Basin Plan 2012). Total nitrogen was detected at five times higher than the guideline value while total phosphorous was detected at seven times higher. Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. The water samples from 4 April show high levels of nitrite and nitrate, and there is a potential for further harm to aquatic organisms.

Ammonia was well below the Australian and New Zealand water quality guidelines for toxicity. While the levels would not be expected to be harmful to fish, the ammonia could promote growth in algae and aquatic plants. The ammonia is likely to be from river sources including rotting fish and flood detritus rather than diffuse inputs from surrounding land.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in both samples for a range of algal species, including blue-green algae, and common toxins produced by blue-green algae. A low concentration of the algal toxin Cylindrospermopsin was detected in the sample collected from Karoola Reach.

The algae levels detected fall within the ‘green’ to ‘amber’ alert levels. An amber alert remains in place at Menindee and Pooncarie as of 24 April 2023.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples at both locations. Both samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per the National Health and Medical Research Council (NHMRC) recreational and Australian and New Zealand Water Quality (ANZG) guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10 x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia.

WaterNSW collected five water samples for the EPA on 3 April 2023.

Samples were checked for pesticides, excess nitrogen and phosphorus, ammonia, metals, algae and algal toxins.

Sample locations

Water was sampled on 3 April 2023 from five locations on the Darling-Barka River between Main Weir and Weir 32:

• Sample 1 – Downstream of the main weir at Menindee
• Sample 2 – Menindee Water Treatment Plant
• Sample 3 – Upstream of Menindee Creek
• Sample 4 – Downstream of Menindee Creek
• Sample 5 – Upstream of Weir 32 at Menindee

More sampling

The EPA and WaterNSW have collected more water samples from the Darling-Barka River downstream in the Pooncarie area on 11 April 2023. The test results from these samples will also be published on the EPA webpage.

In-field measurements

At the time of sampling, WaterNSW collected in-field measurements for pH, dissolved oxygen, conductivity and temperature.

Dissolved oxygen ranged from 1.82mg/L to 7.04mg/L at the five locations. Native fish and other large aquatic organisms require at least 2mg/L of dissolved oxygen to survive but may begin to suffer if levels are below 4 to 5mg/L for prolonged periods. One of the five sample locations detected dissolved oxygen levels below 2 mg/L.

All other parameters are within the expected ranges.

Nitrogen, phosphorus and ammonia

Sample results show that total nitrogen and total phosphorous are higher than the acceptable levels given for lowland river ecosystems in NSW (ANZG 2018, which are in agreement with the regionally specific set of guideline values for the Murray-Darling outlined in the Basin Plan 2012). Total nitrogen was detected at four times higher than the guideline value while total phosphorous was detected at seven times higher.  Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. The water samples from 3 April show high levels of nitrite and nitrate, and there is a potential for further harm to aquatic organisms.

Ammonia was well below the Australian and New Zealand water quality guidelines for toxicity. While the levels would not be expected to be harmful to fish, the ammonia could promote growth in algae and aquatic plants. The ammonia is likely to be from river sources including rotting fish and flood organic matter rather than diffuse inputs from surrounding land.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in all samples for a range of algal species, including blue-green algae.

The algae levels detected fall within the ‘green’ to ‘amber’ alert levels. An amber alert remains in place at Menindee and Pooncarie as of 24 April 2023. No algal toxins were detected.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples from all five locations. All samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per the National Health and Medical Research Council (NHMRC) recreational and Australian and New Zealand Water Quality (ANZG) guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10 x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia.

The EPA collected two water samples on 30 March downstream of Menindee at Pooncarie and approximately 60 kilometres upstream of Pooncarie.

Samples were checked for pesticides, excess nitrogen and phosphorus, metals, algae and algal toxins.

Sample locations

Water was sampled on 30 March from two locations on the Darling River downriver of Menindee:

• Sample 1 – Approximately 60 kilometres upstream of Pooncarie. This site is identified as DRKR on the full sample results.
• Sample 2 – Old Wharf Pooncarie. This site is identified at DRPW on the full sample results.

More sampling

The EPA and WaterNSW have collected more water samples from the Darling River in the Menindee area and downstream in the Pooncarie area on 3, 4 and 11 April. The test results from these samples will also be published on the EPA webpage.

In-field measurements

At the time of sampling, the EPA collected in-field measurements for pH, dissolved oxygen, conductivity, temperature and turbidity.

Dissolved oxygen ranged from 2.75 mg/L to 3.56mg/L at the two locations. Native fish and other large aquatic organisms require at least 2mg/L of dissolved oxygen to survive but may begin to suffer if levels are below 4 to 5mg/L for prolonged periods.

All other parameters are within the expected ranges.

Nitrogen, phosphorus and ammonia

Sample results show that total nitrogen and total phosphorous are higher than the acceptable levels given for lowland river ecosystems in NSW (ANZG 2018, which are in agreement with the regionally specific set of guideline values for the Murray-Darling outlined in the Basin Plan 2012). Total nitrogen was detected at six times higher than the guideline value while total phosphorous was detected at nine times higher. Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. The water samples from 30 March show high levels of nitrite and nitrate, and there is a potential for further harm to aquatic organisms.

Ammonia was well below the Australian and New Zealand water quality guidelines for toxicity. While the levels would not be expected to be harmful to fish, the ammonia could promote growth in algae and macrophytes. The ammonia is likely to be from river sources including rotting fish and flood detritus rather than diffuse inputs from surrounding land.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in all samples for a range of algal species, including blue-green algae, and common toxins produced by blue-green algae.

The algae levels detected fall within the ‘green’ to ‘amber’ alert levels. An amber alert remains in place at Menindee and Pooncarie as of 20 April 2023.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples from both locations. All samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per the National Health and Medical Research Council (NHMRC) recreational and Australian and New Zealand Water Quality (ANZG) guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia. 

WaterNSW collected five water samples for the NSW Environment Protection Authority (EPA) on 30 March.

Samples were checked for pesticides, excess nitrogen and phosphorus, metals, algae and algal toxins.

Sample locations

Water was sampled on 30 March from five locations on the Darling River between Main Weir and Weir 32:

• Sample 2– Downstream of the main weir at Menindee.
• Sample 3 – Menindee Water Treatment Plant
• Sample 4 – Upstream of Menindee Creek
• Sample 6 – Several kilometres downstream of Menindee Creek
• Sample 7 – Downstream of Weir 32 

In-field measurements

At the time of sampling, WaterNSW collected in-field measurements for pH, dissolved oxygen, conductivity, temperature and turbidity.

Dissolved oxygen ranged from 0.73mg/L to 5.85mg/L at the five locations. Native fish and other large aquatic organisms require at least 2mg/L of dissolved oxygen to survive but may begin to suffer if levels are below 4 to 5mg/L for prolonged periods. Two of the five sample locations detected dissolved oxygen levels below 2 mg/L.

All other parameters are within the expected ranges.

Nitrogen, phosphorus and ammonia

Sample results show that total nitrogen and total phosphorous are higher than the acceptable levels given for lowland river ecosystems in NSW (ANZG 2018, which are in agreement with the regionally specific set of guideline values for the Murray-Darling outlined in the Basin Plan 2012). Total nitrogen was detected at five times higher than the guideline value while total phosphorous was detected at seven times higher. Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. The water samples from 30 March show high levels of nitrite and nitrate, and there is a potential for further harm to aquatic organisms.

Ammonia was well below the Australian and New Zealand water quality guidelines for toxicity. While the levels would not be expected to be harmful to fish, the ammonia could promote growth in algae and aquatic plants. The ammonia is likely to be from river sources including rotting fish and flood detritus rather than diffuse inputs from surrounding land.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in all samples for a range of algal species, including blue-green algae, and common toxins produced by blue-green algae.

The algae levels detected fall within the ‘green’ to ‘amber’ alert levels. An amber alert remains in place at Menindee and Pooncarie as of 20 April 2023.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples from all five locations. All samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per the National Health and Medical Research Council (NHMRC) recreational and Australian and New Zealand Water Quality (ANZG) guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10 x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia. 

Sample locations

Water was sampled on 21 March from six locations on the Darling River between the outlet at Main Weir and Weir 32:

• Sample 1 – Outlet to Lake Pamamaroo
• Sample 2 – Downstream Main Weir
• Sample 3 – Darling River at the Menindee Rail Bridge
• Sample 4 – Darling River upstream of Menindee Creek
• Sample 5 – Darling River several kilometres downstream from Menindee outlet. 
• Sample 6 – Weir 32

In-field measurements

At the time of sampling, WaterNSW collected in-field measurements for pH, dissolved oxygen, conductivity, temperature and turbidity.

Dissolved oxygen ranged from 0.41mg/L to 5.97mg/L at the six locations. Native fish and other large aquatic organisms require at least 2mg/L of dissolved oxygen to survive but may begin to suffer if levels are below 4 to 5mg/L for prolonged periods. Three of the six sample locations detected dissolved oxygen levels below 3 mg/L.

One sample taken from the Darling River, upstream of Menindee Creek detected dissolved oxygen levels below 1mg/L. Dissolved oxygen lower than 1 mg/L can be lethal for animals that can’t move to oxygen-rich areas.

All other parameters are within the expected range.

Nitrogen and phosphorus

Sample results show that Total Nitrogen and Total Phosphorous are higher than the trigger values given for lowland river ecosystems in NSW (ANZG 2018). Total nitrogen was detected at eight times higher than the guideline value while total phosphorous was detected at eleven times higher. Algal blooms are possible if these nutrients remain elevated.

Bacteria convert nitrogen compounds such as ammonia into nitrite and nitrate. These compounds can harm aquatic organisms. The water samples from 21 March show high levels of ammonia, nitrite and nitrate, and there is a potential for harm to aquatic organisms.

Algae and algal toxins

A wide variety of algae was tested for. There were positive detections in all six samples for a range of algae species, including blue-green algae.

WaterNSW has advised that the algae levels detected fall within the ‘green’ to ‘amber’ alert levels. An amber alert is currently in place.

Pesticides

As noted above, a pesticide screening test that scanned for over 600 pesticides was completed for samples from all six locations. All samples came back negative for pesticide detection.

Metals

Many metals are vital for humans and animals to stay healthy and only pose a risk if they are found at high levels in the environment. Concentrations of key metals found in water are below.

Total metals have been compared to recreational water quality guidelines and dissolved metals have been compared to ecological water quality guidelines as per NHMRC and ANZECC guidelines, respectively.

Total metals provide a more conservative estimate of exposure from recreational use whereas dissolved metals are used for ecological assessments as this is the bioavailable fraction of the metal (the part that is toxic to organisms).

²NHMRC (2008) Guidelines for managing risks in recreational waters (10 x drinking water guideline value, Table 9.3)

³ANZG (2018). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Australian and New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia.