Cotter Dam enlargement moves ahead

They didn’t choose to do nothing – the following section 5.2.3 describes it:

On hearing Mr Ingram’s first report of the fire at 4.02pm, Mr Graham immediately directed units to the fire, as noted.

(and goes on into great detail).

They did later decide not to keep units out there during the night, which was a decision based on personnel safety. It’s easy to look back and see where things went wrong – often misunderstandings and incorrect information – but it’s easy to be an armchair General. I think it does a disservice to the emergency services people to imply that they just decided to let the place burn down.

From what I’ve been told those running the fires out at ESA Curtin HQ were worried & pulled troops in early (Friday morning). But the only sad thing was that (as far as I remember) Canberra had the cleanest water supply in Australia & possibly the world.

But if we didn’t have the fires then more work may of needed doing for dam prep work.

There back on topic.

This is getting really off topic, but Have any lessons really been learned?

The Melbourne fires seemed to have all the same issues

– warnings were coming after the fires went thru – tv bulletins were hours behind – phones were down due to congestion and poles down – ‘unprecedented conditions led to an unexpected firestorm (oops – just like the one in Canberra a few years earlier).

Clown Killer said :

This is getting off topic, but for the record I do know Chapter 5 and that’s exactly what I’m getting act. I think you’ll find that Sections 5.2.1 and 5.2.2 are littered with references to people expressing concern that the fires should be attacked aggressively to ensure that they were extinguished quickly – but not much was actually done to that effect. They could have chosen to do something and they decided not to.

Hindsite is a wonderful thing isn’t it? It is time we all accepted that shit happened, everyone (including the government) did the best they could at the time (although yes we now years later we know thing COULD have been done differently) and more importantly lessons for the future have been learnt.

I’d have thought that given we have the last flow restrictor in the MDB already (Yerrabi) another enhanced destructor of river health would be the last thing you would want to attach your name to.

The mind boggles. I’d love to see the environmental flow policy associated with this, assuming they have one. No spring flows means no or severely impacted fish recruitment. I doubt the turtles, water dragons etc will be too impressed either. And new lake syndrome should produce some superbly conditioned exotics (which you won’t be allowed to fish for) because we really need more spotty carp in our waterways.

What are they going to put in it? Maybe they are importing a few Navajo to do a rain dance, or perhaps engaging a few pubes appropriately coloured* and dressed in traditional attire will perform the ceremony.

But then again, something has to give the arborbleakum a drink now and a again.

*ala a certain stadiums grass during a certain bid for sporting events. Just not grass coloured. Canberra, home of the Red (Tape) Indians.

I wonder if access to Pryor’s Hut (and Mt. Ginini & Mt. Gingera) would be restricted due to this project?

I know that the alternative route is via Brindabella and Mt. Franklin Rd, but unfortunately I don’t own a 4WD to safely trek through these roads.

I can see the future headlines now: “Construction of dam expansion delayed due to rain.”

Don’t let the Government fool you into believing that we have water restrictions because there’s a drought. We have water restrictions becuase in January 2003 the ACT Government chose to let the catchmnt go up in smoke.

well, ck, bushfires do have a significant impact on the water cycle as, while mature trees take a little water from what rains there are and let the rest run into any catchment, re-growth following a fire means that saplings suck up a shirt load more water for some few years, meaning less into a catchment.

but we are actually still in a drought – i don’t think this is just about water restrictions, more about future proofing, as the predictions are for a drier climate with more incidence of fires (irrespective of how the last one was or wasn’t fought).

and granny, if we go watch the wall’s submersion i’ll bring the ginger beer!

I’m with caf and Thumper! I’d love to see it fill up, especially whilst eating chicken and champagne and stuff!

This is getting off topic, but for the record I do know Chapter 5 and that’s exactly what I’m getting act. I think you’ll find that Sections 5.2.1 and 5.2.2 are littered with references to people expressing concern that the fires should be attacked aggressively to ensure that they were extinguished quickly – but not much was actually done to that effect. They could have chosen to do something and they decided not to.

I’m guessing you missed the outcomes of the Coroners investigations then.

I’ve looked at it, yeah (but I haven’t read it cover-to-cover), and I don’t think it supports your assertion. Have a read through Chapter 5.

Clown Killer said :

However, the regrowth in the affected areas, and there’s heaps, has now negateg any ill affect from run off so i don’t think that it is an issue.

My view, and I’m not saying it’s 100% right, is based on what I’ve been told by foresters familiar with the catchment and the species growning up there. Their view was one of 10-15 years before inflows per rain event get anything near the pre-fire state.

CK, your forresters are right. There will be a loss of yield from the catchment for as long as it takes to regenerate. Studies would indicate that initially run off would be higher and much dirtier and that as regowth picks up yield goes down, all things being equal. The choice of regeneration in the catchment also influences how rapidly yield will increase back to previous levels. Forrest takes longer than grass lands for instance.

What is unequal is rainfall. Sometime there is going to be above average rainfall for a year or too but not produce pre-fire level runoff but maybe 15%-25% less. Still lots of water.

Then the 78GL Cotter will fill not only from its 200 sq km catchment but also from overflow from the 100 sq. km Bendora
catchment.

Lets hope the dam is built before that happens. The dam will not only provide more storage, it will provide more water collecting ability.

However, the regrowth in the affected areas, and there’s heaps, has now negateg any ill affect from run off so i don’t think that it is an issue.

My view, and I’m not saying it’s 100% right, is based on what I’ve been told by foresters familiar with the catchment and the species growning up there. Their view was one of 10-15 years before inflows per rain event get anything near the pre-fire state.

Sure, they decided to leave the magic inaccessible-area bushfire evaporation machine in the garage!

I’m guessing you missed the outcomes of the Coroners investigations then.

Until the new dam fills, using the firebucket on a helicopter right near the dam wall when you have a massive expanse of water all at the same level would be borderline ridiculous.
And the bucket would have to be drawing water from 50m below the (future) surface of the new dam to make contact with the old dam wall.

Won’t be that exciting. All you will see is the water going over the top of the old dam, like it does a few times nearly every year, and filling the space between.

TP 3000 said :

I have been told that the ACT Labour Party are trying to have the dam completed AFTER an election. As they know that as soon as the Cotter dam is enlarged our dam capacity will go from 45% to 20%.

But caf, I would of thought that the old dam wall will be blown up, as it causes a hazard when we have another drought & when helicopters come in to fill their buckets, the buckets might catch on the old wall & bring the helicopter down. Or they may even temporarily empty Cotter (transfer the water to Googong) & remove the wall & empty Googong Dam (via transfer again) to make the new Cotter Dam look all full & pretty.

I think your figures are a bit off if you think we will go from 45% to 20% when the new dam is built. If anything i think the government would want it built before the election to show off their new infrastructure. And that helicopter must be pulling water from pretty deep if you think the bucket could get caught on the old dam.

TP 3000: Nah you can read the plans online – they’re going to leave the old wall in place. It shouldn’t present a hazard to anyone, since the top of it’ll be at least 50 metres under water.

“chose to let the catchment go up in smoke”? Sure, they decided to leave the magic inaccessible-area bushfire evaporation machine in the garage!

But caf, I would of thought that the old dam wall will be blown up
Nup, last plan I read was just to build a new one in front of it. Seems perfectly sensible to me.

as it causes a hazard when we have another drought
What kind of hazard exactly?

Clown Killer said :

…water from where? not enough rain to fill it yet.

Oh there’s been mor than enough rain to fill the cotter dam many times in the last six years. It’s just that the new growth in the catchment sucks up the majority of the water and will continue to do so for possibly the next decade. Don’t let the Government fool you into believing that we have water restrictions because there’s a drought. We have water restrictions becuase in January 2003 the ACT Government chose to let the catchmnt go up in smoke.

Oh, it makes my day when I read someone not fooled (right or wrong). I suspect you are dead on the money.

I have been told that the ACT Labour Party are trying to have the dam completed AFTER an election. As they know that as soon as the Cotter dam is enlarged our dam capacity will go from 45% to 20%.

But caf, I would of thought that the old dam wall will be blown up, as it causes a hazard when we have another drought & when helicopters come in to fill their buckets, the buckets might catch on the old wall & bring the helicopter down. Or they may even temporarily empty Cotter (transfer the water to Googong) & remove the wall & empty Googong Dam (via transfer again) to make the new Cotter Dam look all full & pretty.

PeterH:
As caf says, the water doesn’t need to fill the dam to capacity, just overflow over the old wall for long enough to fill the new bit of space, and then a bit more.

According to the EIS the new 76m dam is being built 125m downstream, and the current wall is 26m high.

Anyone know the actual volume of the downstream component between old wall and new wall?

Interested people shouild be able to work out a guesstimated timeframe for inundating the old wall if you knew inflows, and data from how they intend to manage basic environmental outflows in the interim…
(ACTEW plan on a natural upstream catchment of between 69 – 73GL/pa inflow, environmental outflow from Cotter was ~=14GL/year (averaging 444L/second) in the last report I can find.)

…water from where? not enough rain to fill it yet.

Oh there’s been mor than enough rain to fill the cotter dam many times in the last six years. It’s just that the new growth in the catchment sucks up the majority of the water and will continue to do so for possibly the next decade. Don’t let the Government fool you into believing that we have water restrictions because there’s a drought. We have water restrictions becuase in January 2003 the ACT Government chose to let the catchmnt go up in smoke.

It doesn’t need to fill to overtop the old dam – just has to fill the comparitively small space between the old dam and the new dam wall. The water will probably come from Corin.

caf said :

When it’s finished, I’m keen to go out there and watch as the old dam disappears beneath the water.

um, the water from where? not enough rain to fill it yet.

When it’s finished, I’m keen to go out there and watch as the old dam disappears beneath the water.