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FigBo0T

Puts verniers on his headtube
They opened Windsor bridge this morning, for cars only ...... and now


 

silentbutdeadly

Eats Squid
The bigger the dam...the bigger the spillway. We used to say that if the current overflow spillway at Warragamba went off then Wallacia and Emu Plains were really in trouble...

Dams only mitigate against the smaller floods and they can exacerbate big ones...but hey what would I know about it compared to the Minister for Western Sydney?
 

Freediver

Likes Bikes and Dirt
The bigger the dam...the bigger the spillway. We used to say that if the current overflow spillway at Warragamba went off then Wallacia and Emu Plains were really in trouble...

Dams only mitigate against the smaller floods and they can exacerbate big ones...but hey what would I know about it compared to the Minister for Western Sydney?
How can that work, a dam reduces the amount of flow until its full, then the flow is what the river would have been without the dam.
 

Freediver

Likes Bikes and Dirt
Most major dams have facilities to release aside from overtopping of the dam wall, so they can release more than the inflow volumes.
Which they do for flood mitigation. By letting water out it provides room to store more when a big rain event comes.
 

creaky

The obviative
Which they do for flood mitigation. By letting water out it provides room to store more when a big rain event comes.
Yes, but the point in is that the ML/hour release rate from the dam into the downstream waterway can be significantly higher than the catchment rainfall inflows into the dam i.e. once the dam is full, the flow is not necessarily "what the river would have been without the dam".
 

FigBo0T

Puts verniers on his headtube
Which they do for flood mitigation. By letting water out it provides room to store more when a big rain event comes.
I can't remember Warragamba ever being opened for flood mitigation. It spills when it's full, and when it spills, flooding is guaranteed.

There are other reasons why raising the wall is a bad idea. World Heritage Wilderness is one.

 

Freediver

Likes Bikes and Dirt
Yes, but the point in is that the ML/hour release rate from the dam into the downstream waterway can be significantly higher than the catchment rainfall inflows into the dam i.e. once the dam is full, the flow is not necessarily "what the river would have been without the dam".
Yes,it is possible but why would you. They aren't going to do it for shits and giggles.
The only time I know that this is done is when they flood the redgum flood plains on the Murray.


I can't remember Warragamba ever being opened for flood mitigation. It spills when it's full, and when it spills, flooding is guaranteed.

There are other reasons why raising the wall is a bad idea. World Heritage Wilderness is one.

When it's overflowing I reckon there is a good chance you may have had floods regardless of whats there.
 

FigBo0T

Puts verniers on his headtube
When it's overflowing I reckon there is a good chance you may have had floods regardless of whats there.
Of course. It flooded this week, still flooded now, and no water came out of Warragamba. The dam went from ~40% to 80% capacity in 4 days. A similar rain event in the near future will guarantee a much bigger flood. The bigger the dam, the bigger the flood.
 

Flow-Rider

Wheel size expert
Yes,it is possible but why would you. They aren't going to do it for shits and giggles.
The only time I know that this is done is when they flood the redgum flood plains on the Murray.



When it's overflowing I reckon there is a good chance you may have had floods regardless of whats there.
They try and hold onto the water too long because of all the stress of water consumption and then realise when it's too late they need to dump water. Happen in Brisbane a few years ago.
 

FigBo0T

Puts verniers on his headtube
They try and hold onto the water too long because of all the stress of water consumption and then realise when it's too late they need to dump water. Happen in Brisbane a few years ago.
It's catch-22. We can't reliably predict rainfall. Even short term they can't pinpoint which catchment areas will take the load. Imagine the drama if they dumped water and then had to go to restrictions because the rain missed.
 
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