Blue-green algae

Information and advice about blue-green algae.

Blue-green algae monitoring

Lower Murray Water and WaterNSW are responsible for regular monitoring, reporting and responding to blue-green algae in the Murray River.

We monitor water at key sites along the river. This makes it possible for us to let our rural customers know when the water quality changes.

We sample the water as it enters each of the 9 water treatment plants in our region. These plants treat raw river water via a series of processes and turn it into safe drinking water for towns with urban water supplies.

For more information about drinking water, see Safe drinking water.

Sample locations and dates

BGA sampling takes place across our service region regularly in the Summer and Autumn months. Below highlights the latest sampling dates. Please refer to the map below for sampling results.

Location Sample date
Mildura (Marina) 08/04/2024
Psyche Pumps 08/04/2024
Lock 9 08/04/2024
Lake Cullulleraine08/04/2024
Robinvale 09/04/2024
Boundary Bend 09/04/2024

Current warnings

Areas impacted by the Red Alert (red line) are shown on the map below. As the river is our main water source, all the channels and pipelines within the range of the Red Alert Area are affected.

When a Red Alert is issued, we put up warning signs in popular recreational areas along the river.

If you’re not sure whether the water near you is affected, it’s best to be safe and avoid the water.

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About blue-green algae

Blue-green algae – scientifically known as Cyanobacteria – are a group of photosynthetic bacteria. These groups are often called ‘blooms’.

Some blue-green algae blooms produce harmful poisons that can cause severe illness in humans and death for animals. All types of blue-green algae have the potential to cause illness when found in large quantities – whether toxic or non-toxic. We issue alerts for large volumes of non-toxic blue-green algae due to the lipopolysaccharides in the cell wall of all blue-green algae.

Blue-green algae blooms are more likely to happen when water is warm and enriched with nutrients, such as phosphorus or nitrogen.

Under certain conditions, blue-green algae can gather in thick layers on the water’s surface or edge. Blooms are most often blue-green in colour, but they can also be blue, green, reddish-purple or brown. Blue-green algae is not always visible and does not always colour the water blue or green.


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    Do not drink water affected by blue-green algae.

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    Do not use water affected by blue-green algae for washing, cleaning, cooking or bathing.

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    Boiling the water does not remove the algae toxins or make the safe to drink.

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    If you have no other source, you can use water affected by blue-green algae for watering gardens and lawns, but not for fruit and vegetables.

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    If you do water your garden or lawns with affected water, avoid direct contact.

Rural water supply

Our rural water supply is vulnerable to blue-green algae blooms, particularly during the summer months. Rural water is untreated and not suitable for drinking at any time. Do not drink water affected by blue-green algae.

Blue-green algae is a concern for:

  • rural customers who use untreated river water for irrigation or domestic and stock purposes
  • recreational water users.

We aim to supply water to our customers at a quality that is at least the same as the quality of the source Murray River water.

For more information about rural water supply rights and obligations, see our Customer Charter – Rural.

For more information about blue-green algae and irrigation, see:

Urban water supply

Our urban water supply is safe for drinking and domestic use. Blue-green algae toxins are removed by the treatment processes at our water treatment plants.

We monitor our town drinking water (potable water) supplies to make sure they meet Safe Drinking Water Regulations.

For more information about water quality, see Water treatment and testing.

Water storage

We recommend that water users in irrigation and rural districts who use water for stock have enough water storage for 6 weeks of normal use.

If the water is affected by blue-green algae events, it will be unsuitable for use for stock for a considerable time.

For more information, see Managing blue-green algae in farm water supplies on the Agriculture Victoria website.

Blue-green algae infection symptoms

Some species of blue-green algae can produce several different toxins that can affect the skin, liver, heart, gastrointestinal tract, nerves and muscles.

Typical symptoms resulting from contact with algae include:

  • itchiness and rashes
  • headache
  • fever
  • seizures
  • respiratory failure
  • sore eyes, ears and nose
  • gastroenteritis – including nausea, vomiting and diarrhoea symptoms.

If you have symptoms and you suspect you may have a blue-green algae infection, contact NURSE-ON-CALL on 1300 60 60 24 or seek medical advice.

People may be exposed to blue-green algae through:

  • contact with the skin, such as when swimming
  • inhalation – for example, when near irrigation sprays or when boating or water skiing
  • drinking contaminated water.

Animals affected by blue-green algae have usually come into contact with affected water from a dam.

NSW Health has information on blue-green algae and recreational water sport. See Recreational water quality.