Catchment rain generates inflows into Sydney dams

Catchment rain generates inflows into Sydney dams

09 February 2020

Sydney’s dam storages are set to receive their best inflows in nearly three years as heavy rainfall across the catchment is forecast to continue throughout the day.

Warragamba Dam is already receiving inflows of 40 gigalitres per day and based on Bureau of Meteorology (BoM) forecasts WaterNSW predicts it will rise above 50% of capacity in coming days for the first time since August last year.

With the BoM predicting that the Warragamba Dam catchment could receive a further 130mm of rain today, the dam storage is likely to receive its best inflows since April 2017.

If the Warragamba storage level – at 43.7% of capacity as of 9am - reaches 55% as predicted, it will have effectively recouped nine months of water supply in less than a week.

Across other metropolitan storages the total volume has already risen from 35.7% of capacity to 41.4%, with catchments receiving an additional average of 83mm in the past 24 hours.

Should the BoM weather forecast be realised, WaterNSW modelling suggests it is possible that Nepean dam (up 6.5% to 9am since last week) could spill, and all metropolitan dam storages will fill including Cataract (+5%), Cordeaux (+4.7%), Avon (+5.8%) and Woronora (+3.2%).

The Shoalhaven has received 114mm in the past 72 hours generating inflows into Tallowa Dam at a rate of 12 gigalitres per day.

While it is likely some ash and debris has been washed into the upper reaches of the Warragamba system, there is no impact on the water quality being supplied for treatment. Any surface debris is being avoided by extracting water from 30m below the surface as a precaution.

Monitoring continues by experienced water quality scientists using sophisticated, real-time technology pioneered by WaterNSW which predicts any change in storage water quality.

WaterNSW has already deployed two silt curtains to intercept floating material that could pose a water quality risk to the storage and is assessing the effectiveness of additional ash and sediment control measures around the storage.

Warragamba also has the capacity to select water from varying storage depths and as such is currently releasing water from 30 metres below the surface as a precaution.

Media Contact – Tony Webber 0428 613 478.


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