WaterNSW has expanded preparations to limit potential impacts on the water quality in dam storages as rain is forecast across NSW from Thursday 16 January to Monday 20 January.

Following recent bushfires at Warragamba Dam, in the Shoalhaven, on the South Coast, Blue Mountains and the Riverina, the NSW Minister for Water, Melinda Pavey, said the government’s priority is protecting drinking water supplies.

The government has allocated this task to government agency WaterNSW, which has the specialist water quality and scientific expertise to ensure the quality of water supplied to Sydney Water for treatment in Greater Sydney.

WaterNSW actions to date intended to mitigate the potential risk to dam water quality include:

  • Containment booms/silt curtains have been installed at two locations on Lake Burragorang (Warragamba Dam) to limit the amount of ash near the dam’s supply off-take point
  • Joint event response monitoring plans to characterise changes in water quality have been developed in consultation with Sydney Water and NSW Health
  • Erosion modelling to determine areas of highest risk and inform further mitigation strategies
  • Online monitoring and hydrodynamic modelling to pre-emptively assess ash movement and provide information on the duration, magnitude and location(s) of such an event
  • Joint operational contingency plans to maintain supply in the event of poor water quality, e.g. offtake reconfiguration/ supply from Prospect Reservoir and/or metropolitan storages
  • Assessing weather predictions daily and identifying rainfall triggers that will activate additional management actions
  • WaterNSW is in contact with other water authorities who have had recent experience managing post-bushfire water quality risks, such as Melbourne Water
  • WaterNSW, Sydney Water and NSW Health recently completed an incident exercise to test responses in the event of a bushfire followed by significant rainfall

The extent of any water quality impacts on water in the dam will depend upon the location, timing and intensity of rainfall events.

Monitoring continues by water quality scientists using sophisticated, real-time technology pioneered by WaterNSW which can predict any change in the dam storage’s water quality.

WaterNSW CEO, David Harris, said that while low-intensity rain is forecast for the next seven days, this is not considered sufficient to wash material into dam storages.

“Therefore we do not anticipate a water quality problem over the coming week, however we will need to carefully manage the catchment over the coming years in order to protect our water supply from these sorts of impacts,” Mr Harris said.

“We are taking a range of precautionary measures on site, including the deployment of silt blankets and floating booms at key water inflow points to the dam storage, additional monitoring and modelling, and planning with other agencies.”

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