Some Goulburn Valley Water customers supplied with water originally sourced from the Murray River may be experiencing an 'earthy' taste and odour to their water. This includes the townships of Numurkah, Wunghnu, Cobram, Strathmerton and Yarroweyah.
The taste and odour are caused by a naturally occurring, harmless compound called geosmin which can be caused by Blue-Green Algae (BGA). Geosmin can be more prominent during the warmer months due to the presence of seasonal algae in the raw water. This includes rivers and channel systems used to fill our town raw water storages.
We have also developed an information sheet (PDF, 120kb) with more information about BGA, geosmin and the current impacts on towns in our northern region.
Whilst customers may experience taste and odour issues water supplied by GVW remains safe to drink.
GVW water treatment plants are specifically designed to remove these algae. Powdered activated carbon dosing at the water treatment plants have been increased to deal with the elevated levels of geosmin. We are currently seeing the carbon dosing run at unprecedented levels to remove the geosmin. Regular sampling is also being undertaken to monitor the water quality and adjust treatment as necessary.
Taste and odour complaints from Numurkah and Wunghnu residents were first reported on 9 January. Cobram residents started calling about water quality on 4 February.
BGA in the Yarrawonga Weir.
Unfortunately, geosmin can be detected at very, very low levels. For example, it can be detected at about 0.00001 milligram/litre (one millionth of a milligram), whereas chlorine can be detected at 0.1-0.4 mg/litre. Some people may also be more sensitive to the geosmin than others.
We want to reassure people that water always remained safe to drink and has always met parameters set by the Australian Drinking Water Guidelines and the Safe Drinking Water Act. It is an inconvenience for customers and we are really sorry. The water quality and operational teams are working round the clock to improve the supply. We appreciate peoples patience and understanding while we work to fix the issue.
Whilst we are working to improve our treatment processes to improve the taste and odour, algae can be unpredictable. We cannot be certain how long this algal bloom will last, as growth and timing are dependent on a number of environmental factors such as water temperature, nutrient levels and storage volumes.
We are working to keep affected communities updated following any changes. The issue is affecting many communities along the Murray River and we are also working closely with water authorities in Victoria and NSW to continue improving supply.
Goulburn-Murray Water is warning the public to avoid contact with water in Yarrawonga Weir/Lake Mulwala and Turner Island east backwater near Kirwans Bridge after monitoring detected high levels of blue-green algae. Warning signs are being placed at major recreational areas.
WaterNSW has issued a caution for the River Murray downstream of Lake Mulwala to Tocumwal, as harmful concentrations of BGA may be present. It is recommended that alternative supplies for stock drinking be used. Stock and pets should be kept away from the water. Watering of edible garden plants should be avoided.
These recreational warnings do not relate to the quality of drinking water supplied by Urban Water Corporations, but recreational users of the Murray River should be aware of alerts which can be found at;