Dam levels

miz 2 December 2010 43

OK, I admit I wasn’t good at maths, graphs and stuff at school – but does anyone know why, after all the rain we have had in the last month, dam levels are still hovering around the 90% mark?

I would have thought it would be over 100% by now, and that we would be hearing about ACTEW having to let the overflow down river.

According to BOM, in November 2010,

Mount Ginini received 210mm rain;
Tuggeranong (and presumably Googong) received 148mm;
Tidbinbilla received 155mm; and
‘Canberra’ (Airport) received 121mm.

So, what’s going on? Is it a conspiracy to prevent us from thinking that water is plentiful, so we can continue to be charged the proverbial ‘arm and a leg’ for this essential commodity?


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Keijidosha Keijidosha 10:34 am 02 Dec 10

A quick visit to the ACTEW Corp website shows that Googong is not full:
http://www.actew.com.au/water/damlevels.aspx

Despite being the largest dam in our supply system, Googong is in a rain shadow which reduces yeild.

Hercsie Hercsie 10:40 am 02 Dec 10

I have wondered this too – flying into canberra over googong dam last week I could not see any of the foreshore exposed – unless “100%” is now at the top of the trees around the dam?

androo androo 10:44 am 02 Dec 10

Cotter, Bendora and Corin dams (on Cotter River) are all at 100%, but Googong Dam is hovering around 80% – hence the total catchment is around 90%

This shows it – http://www.actew.com.au/water/damlevels.aspx

ABC129 ABC129 10:50 am 02 Dec 10

Just have a look at the graph on the linkyou posted.
Googong has by far the largest capacity of all the dams and earlier this year it had about the same amount of water in it as Corin. The others look like they’ve been basically overflowing since September.

thatsnotme thatsnotme 11:00 am 02 Dec 10

ACTEW seem to be pretty slow to update dam levels on their website these days too. The roadside signs look to be more up to date than what’s online – the sign I passed yesterday was saying levels were at 92%, so they are going up slowly.

cmdwedge cmdwedge 11:04 am 02 Dec 10

I’ve heard (and feel free to correct this) that Googong has the largest capacity, but has the smallest catchment area of all the dams.

Jerry Atric Jerry Atric 11:08 am 02 Dec 10

Wasn’t excess water from the Cotter supposed to flow into Googong via Stromlo?

Captain RAAF Captain RAAF 11:13 am 02 Dec 10

I think someone needs to head out to Googong and get a photo of the dam! Are we agreed that ‘full’ means that water is lapping at the top of the spillway? This will likely be a lot lower than the level of the road over the wall, btw.

I might head out there over the weekend, it would make a great photo opportunity in the beast!

dave__ dave__ 11:17 am 02 Dec 10

Could ACTEW be keeping the level of the dam low while they finish work on the spillway?
http://www.actew.com.au/watersecurity/majorprojects/GoogongDamSpillwayUpgrade.aspx
Or has that finished already?

astrojax astrojax 11:18 am 02 Dec 10

i was wondering, with my own poor maths, how dams could be much more than 100% – surely they would then overflow and hover at round 100%? (heard a comment on the talking box yesterday about dams at 110%…)

coffeeman coffeeman 11:21 am 02 Dec 10

Certainly warrants, given the comment of Googong being in a rain shadow and the other dams overflowing, having the ability to pump excess to the dams not currently full.

Snarky Snarky 11:33 am 02 Dec 10

If you’re interested you can get daily updates of all Australian water storages and systems via the BOM’s free Water Storage iphone app.

p1 p1 11:43 am 02 Dec 10

A week ago Googong looked like this.

KB1971 KB1971 11:47 am 02 Dec 10

Captain RAAF said :

I think someone needs to head out to Googong and get a photo of the dam! Are we agreed that ‘full’ means that water is lapping at the top of the spillway? This will likely be a lot lower than the level of the road over the wall, btw.

I might head out there over the weekend, it would make a great photo opportunity in the beast!

I have it on good authority that it is 2.5m from capacity at the wall. Spread that 2.5m in height by the surface area of the dam & there is quite a bit of water to go before it goes over.

Holden Caulfield Holden Caulfield 12:15 pm 02 Dec 10

Mark Sullivan tells us there has been more than 2.5 gigalitres flow into Googong in the last 24 hours. Meanwhile over 1 gigalitre per day is spilling over at the Cotter.

And he also thinks we have had enough rain already:
http://twitter.com/#!/Sullivan_ACTEW/status/9765589912395776

D2 D2 12:29 pm 02 Dec 10

Keijidosha said :

Despite being the largest dam in our supply system, Googong is in a rain shadow which reduces yeild.

+1

What I want to know is who’s the idiot who decided to build our largest dam where it doesn’t rain!

georgesgenitals georgesgenitals 12:50 pm 02 Dec 10

Googong has the LARGEST catchment area of all the dams, but is HEAPS bigger than all the others, meaning it takes longer to fill (and empty). If we keep getting weather like this for the next month or so I would expect used storage capacity to hit 100%.

georgesgenitals georgesgenitals 12:53 pm 02 Dec 10

D2 said :

Keijidosha said :

Despite being the largest dam in our supply system, Googong is in a rain shadow which reduces yeild.

+1

What I want to know is who’s the idiot who decided to build our largest dam where it doesn’t rain!

2 reasons. Firstly, it can be much larger than the (then) existing dams. Second, until the drought over the past 15 years or so it was used to regulate flow down the Queanbeyan River to stop the semi-regular flooding that used to occur. Googong catchment is a very large area, and forcign that water down the Queanbeyan River would produce, um, interesting results.

This: http://www.actewagl.com.au/water/catchment/watermap.aspx?facts

shows that the catchment areas are:
Cotter: 192.4 square kilometres
Bendora: 91.4 square kilometres
Corin: 196.3 square kilometres
Googong: 873 square kilometres

That’s why they built it there!

chewy14 chewy14 12:59 pm 02 Dec 10

dave__ said :

Could ACTEW be keeping the level of the dam low while they finish work on the spillway?
http://www.actew.com.au/watersecurity/majorprojects/GoogongDamSpillwayUpgrade.aspx
Or has that finished already?

I’ve heard that this is correct, they are letting more water go down the river from the dam.
Because of the spillway works, they have been trying to keep Googong a bit low just in case we have floods or massive rains (which we have been).

Captain RAAF Captain RAAF 1:07 pm 02 Dec 10

chewy14 said :

dave__ said :

Could ACTEW be keeping the level of the dam low while they finish work on the spillway?
http://www.actew.com.au/watersecurity/majorprojects/GoogongDamSpillwayUpgrade.aspx
Or has that finished already?

I’ve heard that this is correct, they are letting more water go down the river from the dam.
Because of the spillway works, they have been trying to keep Googong a bit low just in case we have floods or massive rains (which we have been).

I say let it back up all the way to the top, teach some people the stupidity of their decision to build housing estates on flood plains all based on the theory of a few years ago that we are in a never ending drought and all about to die and surely it won’t ever rain again… I personally can’t wait to see Harrison go under. I watched it getting built and was amazed to see great swathes of water across the site even after moderate rain. There would be a number of other areas all unprepared for serios flooding and I’ll enjoy watching all the poor floating downstream from my castle on the hill.

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