View new dam location on Google Earth
So they won’t be raising the Warragamba Dam by 14 metres, after all, not to stop flooding in wet years, not to store more water to save on desalination costs in dry years and certainly not to restore the 50MW hydroelectric power station disconnected in 2001 because of low water levels.
Charting WaterNSW’s data shows that more than 8,000 GigaLitres of water was spilled over Warragamba dam during the 2 wet years 2021 & 2022.
To store rather than spill that volume of water, in addition to the 2,000GL of the existing storage volume and to create a safety margin to prevent flooding, a dam would need to be able to impound about 12,000 gigalitres in Lake Burragorang and it may need a crest elevation of 260 metres – which is double Warragamba dam’s 130m.
A capacity at dam crest level of 12,000GL minus a safety margin of 2,000GL leaves an active storage volume of 10,000GL – or 12 years’ worth of Sydney’s potable water demand, without water restrictions. That’s more than enough water to keep Sydney well supplied through another Millennium Drought.
You may be able to raise the Warragamba Dam by up to 30 metres to 160m crest elevation for a storage capacity of 5,000GL – 3,500GL active storage volume with 1,500GL safety margin – somewhat useful but there would be no way to further raise that dam to store a much more useful 12,000GL.
So Warragamba is not the best place to build a dam to store the most water in Lake Burragorang but you can build a much higher dam some kilometres further upriver.
The New Dam Scheme
About 6km or so upriver from Warragamba Dam, I’ve identified a suitable site for building a New Dam for Sydney – working title “Upriver Warragamba Dam 2“.
Creek By-pass
The Werriberri Creek by-pass diverts the flow from the creek through a tunnel or culvert to drain the Werriberri Creek valley at the site for the construction of the power station.
Power Station
A hydroelectric power station with its intake below the spillway crest and its outflow down the Werriberri Creek.
Spillway
The embankment dam diverts the higher than 225 metres elevation flow of the River Warragamba through a valley towards a saddle where the spillway and the intake for the power station are constructed.
Embankment Dam
The Embankment Dam incorporates a flow pipe for lower elevation water flow down the River Warragamba. The embankment dam must be built high enough (with its crest at an elevation of at least 260 metres) so that it is never overtopped even when the river is in spate.
Flow Pipe
The Flow Pipe through the embankment dam incorporates a flow control valve so that the required environmental and supply flow rates (up to ~26m3/s) are possible during construction and in operation when the river level may be too low to reach the spillway and the power station.
National Project
Naturally, you may build such a dam and wait many dry years before a wet year begins to fill Lake Burragorang as intended.
So the construction of such a dam is probably best funded as a national project by a visionary Australian government, looking to the long term and not in any hurry to get a return on its investment.
Build it and the rains will come! 😀
Scottish Scientist 