• Tony Bosworth

Controlled spill from Warragamba Dam mid afternoon - 99.2% full - slow flow today, more Sunday



There will be a controlled spill of water from Warragamba Dam this afternoon - Saturday - as it has now filled to 99.2 per cent of capacity, and that could well lead to flooding in the Hawkesbury on Sunday when they increase the flow rate.


A spokesman for WaterNSW just told us mid-afternoon today will see the spill gates opened. We will have more on the amount soon, but the plan is to have a slow spill today, leading into a bigger sustained spill tomorrow - Sunday.


That means potential flooding for the Hawkesbury come Sunday, especially if the rain continues, as forecast.


"With the Upper Nepean region already receiving the impact of the severe weather event, dams such as Nepean, Cataract, Cordeaux and Avon are also expected to reach capacity and begin spilling later this afternoon (Saturday, 20 March)," said a NSW spokesman at 12.30pm Saturday.


"The revised predicted spill timing for Warragamba is several hours earlier than originally forecast and the volume of spillway flow will increase into Sunday as inflows continue," the spokesperson said.


Forecast heavy rain today and Sunday is set to push all of Sydney’s water supply dams close to capacity, with many potentially spilling over the weekend, including Warragamba.


A WaterNSW spokesman said earlier this morning: “modelling suggests, at its current level, more than 90mm of rain across the Warragamba catchment will result in sufficient inflow to push the storage level above capacity and trigger a spill”.


Sydney’s major supply storage, Warragamba Dam - which flows into the Nepean and then Hawkesbury river when it is spilled - currently sits at 99.2% of capacity as part of a total metropolitan dam supply network sitting at 94.6%.


The Bureau of Meteorology forecast coastal trough, which developed along the North Coast yesterday, has brought with it heavy rain across the Greater Sydney catchment from Friday night and into Saturday.


Public access to WaterNSW dam sites and linked public areas is off limits until further notice as a safety precaution.


WaterNSW has set-up a dedicated 24-hour incident management team that is working closely with the Bureau and the NSW State Emergency Service to monitor weather and inflows to dams.


WaterNSW said they would also continue to work closely with Sydney Water and NSW Health throughout this 'rain event', to watch for potential water quality impacts on untreated supply.


Warragamba Dam sends its water to Prospect Reservoir for treatment before it is pumped to Sydney homes, but Prospect is also approaching capacity.


More as we get it…



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