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Proposal for Cotter Dam to be Enlarged

shauno 10 December 2006 20

As reported here in the Canberra Times.

Proposal to enlarge the dam from 4.5 gigalitres to 80 which is a massive increase. I think this is a great idea I only hope they allow mixed use for this dam like fishing boating etc. Even though it is drinking water there is no reason it can not be used in this way. And would be great for tourism.

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20 Responses to Proposal for Cotter Dam to be Enlarged
shauno shauno 1:07 pm 28 Dec 06

That dam overflows alot and easily ive seen it many a time.

dan dan 1:04 pm 28 Dec 06

am i missing something? Isn’t enlarging a dam a useful project if and only if the dam is regularly at so close to capacity that losses due to overflow are a major limitation to the water supply? just raising the bloody wall won’t increase the catchment size.

shauno shauno 11:15 am 13 Dec 06

Yes to increase the dam by the size they are talking I would think it would require a whole new structure. Possibly utilizing the existing dam to hold back the water while building a bigger one behind thats if there is enough room behind the existing dam. Or maybe it can just be modified. One would think that you wouldn’t need to double its height to double the capacity as the reservoir size would increase disproportionately to the height of the dam.

Thumper Thumper 10:52 am 13 Dec 06

However, can anyone say if the Cotter dam wall is designed to take extra pressure?

shauno shauno 10:05 am 13 Dec 06

Yep I agree the Cotter dam proposal is a pretty good idea. Better then all the other proposals so far.

I also think it would be great for recreation, very easily accessed from Canberra for water skiing and fishing. There would be people saying you couldn’t do that in a drinking supply dam but thats just bullshit. If they are seriously talking about recycled water for drinking then activities such as what goes on at jindabyne would be no worries.

Thumper Thumper 9:57 am 13 Dec 06

Actually, the proposal to increase the capacity of Cotter Dam is reasonable, given that the dam is already there.

The disruption to biodiversity would be minimal as there has already been previous disruption. As such the area has already shown that in time, it can regenerate.

Indeed, it will cost a lot of money, in fact, probably as much as building a new dam. However, the benefits of extending Cotter would probably outweigh the negative factors involved in creating a new dam out in Namadgi.

And it is a step in the right direction rather than simply slapping restrictions on everything.

Any bets as to whether this will actually get off the ground?
I hope so, given the massive increrase in Canberra’s population since there was last any real water infrastructure work done.

shauno shauno 9:46 am 13 Dec 06

I Know the pipe line isn’t built yet but I’d say it will be. I’m in the exploration side of the business so Ive got inside knowledge of various projects aswell.

As for draining aquifers I was referring more to the diverting of some of the huge wet season out flow rivers of the top end that flow out to sea. Also the the pipe line proposal from PNG is from similar river outflow not from sub surface aquifers.

I really think desalination plants are the go as well similar to a trial in Perth using tidal energy to push water through nano structure membranes to desalinate.

The storing of water in sub surface aquifers could work along the same lines as the US use for their strategic oil reserves pumped into dissolved salt dome structures. Only difference with water though is it cant be constrained as easily as oil far from it.

Maelinar Maelinar 9:30 am 13 Dec 06

haha pipe dreams – I like the pun

The Gas pipeline you speak of isn’t even being built yet, I know because it directly relates to the work I am in.

The irreversible damage you speak of by lowering the water table and draining natural aquifers will merely hasten my ‘Steel Dawn’ prognosis, if you would like me to back that up with scientific fact, I can provide several reams of scientific conclusion.

The reason why you need a permit to drill a bore for example is not just the government maintaining its administrative burden, they are watching the water table VERY closely due to salinity and desertification concerns.

Until we admit there is a problem however, we are going to remain closet bound.

Even my initial suggestion of capturing the water in sub-surface aquifers is reasonably Canberracentric, for that same water would be used downstream by several communities that would miss out if we enhanced our catchment capabilities – their loss for being gravitationally inferior.

shauno shauno 9:03 am 13 Dec 06

No Im talking about Massive engineering projects like bring water down from Northern Territory. There is also a plan to import PNG water by pipe along the same line as the GAS pipeline through Cape York and down further south.

These projects sound like pipe dreams but they are well within our engineering capabilities and budget. And we will need to do this if we plan to have a population of 50 million or so in the future.

I have an optimist point of view which comes from working in an industry where we regularly now drill in over 3km of water through a further 5KM plus or rock to extract oil using robotics and subsurface production facilities where this was considered impossible not to long ago.

Maelinar Maelinar 8:51 am 13 Dec 06

Where north ?

Toowoomba ?

They’re thinking of drinking their own wee up that way.

Taking water from somewhere else is a VERY bad idea.

shauno shauno 8:48 am 13 Dec 06

“A great example of this is the River Murray, which is set to run dry in 2008, no matter how much falls, we have already committed to taking more than that out of it.”

Thats why I like the idea of a big engineering project to bring water from the North down into the head water catchments of the Murry Darling System. Now if this was to happen on a sufficiently large scale we could then stop using the Snowy Mountain scheme for irrigation purposes and use it for drinking water.

Thumper Thumper 8:35 am 13 Dec 06

Get ice bergs from antarctica. Ship them to SYdney/ Cut them up and put them on trucks. Drive to the head of the Murray and the Darling.

Let them melt and wait.

Problem solved.

I should be king of the world…


Maelinar Maelinar 8:28 am 13 Dec 06

The evaporative effect of increasing the dam size in cotter is different to, for example, having a dam out on Lake George. As it were, the water footprint from a V shaped dam is much more economically sensible than a — shaped dam. Additionally, the evaporative effect of photosynthesis and transpiration (now we’re getting technical) will positively effect the biodiversity of an entire valley, although the cotter valley doesn’t appear to have the same lack of biodiversity as the Molongolo valley for example (perhaps because there is already a dam there).

The real secret is to build sub-surface aquifers, although unless there was a conveniently located mine we could fill (ie dug by other people), I can’t see this broke government being able to afford to dig a big hole in the ground – although such a simple engineering feat sounds like an easy thing to do it tends to become very expensive.

Although I pray for rain similarly to the ACT governments water catchment plan, the reality of this is that it won’t work regardless of how much wet stuff falls out of the sky; no matter how much falls, we have already over-subscribed to taking it out. A great example of this is the River Murray, which is set to run dry in 2008, no matter how much falls, we have already committted to taking more than that out of it.

Kind of a rock and a hard place isn’t it ? My suggestion is to get all Patrick Swayze, buy a sword and get all ‘Steel Dawn’ on your vagrant neighbour who wants to steal your water.

JC JC 9:13 pm 12 Dec 06

He Futto if you live in an odd numbered house you could have turned your sprinklers on between 7pm and 10pm last Sunday night. But if you were even then the answer to your question would have been NO. Under stage 3 the general exemption on sprinkler use on Saturdays (even) and Sundays (odds) between 7-10pm has been included up until late Jan.

roccon roccon 8:50 pm 11 Dec 06

Googong was the answer for our increasing population as well as a dam south of Tharwa, but as the Googong catchment is currently “broken” other alternatives need to be sought.

How much water will we see coming down the Murrumbidgee ?? SnowyHydro will start holding back on releases soon me thinks. Murrumbidgee will also dry up me thinks.

lateralis lateralis 7:10 pm 10 Dec 06

What is interesting is that the plan for Canberra has been managed from at least Walter B-G’s days, and was supposed to support a population of 600,000. Where did they think the water was goign to come from?

miz miz 10:41 am 10 Dec 06

Hopefully no legless lizards or sim in the vicinity!

Finally a practical proposal: an acknowledgement that water rationing can only go so far (and it is starting to piss people off), and a realistic regional plan for the long-term.
But no mention of timeframes if it were to go ahead, I notice.

KaneO KaneO 10:35 am 10 Dec 06

Problem with that is the flow on (or lack of) effect for those downstream of us.
Given the amount of water lost thru evaporation I’m wondering if covering dams/waterways is a feasible option. I mean feasible in an engineering sense, the govt can’t even sort out Tharwa Bridge so I’m not going near the cost issue.

futto futto 10:27 am 10 Dec 06

Does this mean i can turn on my sprinkers tonight? 🙂

johnboy johnboy 9:37 am 10 Dec 06

Obviously it makes economic sense only if we have access to someone else’s money. a(or we’d have done it already)

Also interesting to see the Murrumbidgee pumping facility isn’t complete. I’d had the distinct impression the Chief Minister had announced that.

Probably did the planning and declared it done, as is his wont.

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