Benmore Dam spilling

[Okey Dokey]

It has been about 5 years since the lake levels have been high enough to require the spillways to be opened. I rode up to have a look yesterday and thought I would post a couple photos.

Benmore is the largest earth dam in NZ and one of the largest in the southern hemispere. Construction began in 1958 and it was commisioned in 1965. The water in the lake is equal to 1.5 times the water in Wellington Harbour!

As you can see, there are 4 spillways, but only 2 were operating. There was a man on site and he seemed to be controlling the spilling. This surprised me; I guess I assumed it would all be done remotely. There is a raised lip, or ridge, at the base of the spillway to prevent the water scouring out the river. That provides the nice splash at the base.

[Pussy]

Cool pics, OD!
Bet there was a rumble coming from that

[Okey Dokey]

Yes, it was thunderous! (is that a word?)

Really impressive. I can imagine what it would be like if all 4 were open.:eek5:

[Jantar]

..... There was a man on site and he seemed to be controlling the spilling. This surprised me; I guess I assumed it would all be done remotely. ....

Spill is controlled remotely, but like all remote operations, local control must be tested from time to time. The guy operating the spill from on site will be doing it under instruction from moonbase in Twizel.

We have been spilling from both Clyde and Roxburgh stations since mid December. The problem isn't so much that there has been too much water, its just that the transmission system is so downgraded that the power can't be moved to where its needed. So Benmore, Tekapo, Hawea, Clyde, and Roxburgh are all spilling water, and gas fired power stations are going tits out in the North Island.

[Trumpess]

They are awesome to watch!

Many moons ago my dad worked for Ministry of Works in Twizel (helped electrify Ohau B) and he took us around the dams at the time they were spilled. The noise and vibrations scared the crappers out of me at the time, a kid of 12 lol. Something I will always remember.

[Okey Dokey]

Spill is controlled remotely, but like all remote operations, local control must be tested from time to time. The guy operating the spill from on site will be doing it under instruction from moonbase in Twizel.

Aaaah, thanks for that, Jantar. It's great how on kb there is always someone who knows the answers!

[Okey Dokey]

They are awesome to watch!
The noise and vibrations scared the crappers out of me at the time

Yes, it is really very big and loud and exciting and not something you get to experience everyday.

[Winston001]

We have been spilling from both Clyde and Roxburgh stations since mid December. The problem isn't so much that there has been too much water, its just that the transmission system is so downgraded that the power can't be moved to where its needed. So Benmore, Tekapo, Hawea, Clyde, and Roxburgh are all spilling water, and gas fired power stations are going tits out in the North Island.

Groan. This is precisely what I hoped wasn't happening - spilling water in the SI while the NI gas generators are spinning. What a bloody shambles. Not enough electricity in the winter, natural gas supplies running out, sod all major new generation.

Has any journalist picked up on this?

On another matter - Jantar - is the Roxburgh dam releasing sediment from the bottom gates? Seems like a good time to do it. Especially at night. :devil2:

[Jantar]

No. We never release sediment from the bottom gates.

What you are reffering to is called "flushing" and it is only ever done via the main spillway gates. The lake level is lowered at times of very high flow and parts of the river with a high sediment build-up are turned back into a river. this mixes the fine sediment with the water and is then discharged via the spillway gates.

There isn't enough water in the river for that, but there's too much to generate and still be able to get the power to the consumer. Right now Clyde is on 33% generation and spilling 480 cumecs. Roxburgh is on 40% generation and spilling 440 cumecs.

[Winston001]

Most interesting. Fortunately I'm no engineer but the simple way of removing the sediment (which is a problem for Lake Roxburgh) would be to allow a great splodge of toothpasty mud to squeeze out the bottom of the dam. The fish might be a bit annoyed but hey - they'd get over it.

Otherwise it'll just fill the lake up.

[Jantar]

Most interesting. Fortunately I'm no engineer but the simple way of removing the sediment (which is a problem for Lake Roxburgh) would be to allow a great splodge of toothpasty mud to squeeze out the bottom of the dam. The fish might be a bit annoyed but hey - they'd get over it.

Otherwise it'll just fill the lake up.

That would probably work if there was a build up at the dam face, but the siltation is happening many kms upstream from the dam. Now with Clyde dam upstream of Roxburgh, there is very little extra silt reaching Roxburgh, but Clyde will need to start flushing in around 130 years time.

[FJRider]

Otherwise it'll just fill the lake up.

Thats exactly what happens...

Fortunately, such dams do have a life expectancy... Roxburgh I think (Jantar may correct me) has passed its original period of expectancy. Even with upgrades, its still a 50 year old dam.

And downstream of the dam, they don't want the silt either... It tends to block the outlet of the river and cause flooding...

[FJRider]

That would probably work if there was a build up at the dam face, but the siltation is happening many kms upstream from the dam. Now with Clyde dam upstream of Roxburgh, there is very little extra silt reaching Roxburgh, but Clyde will need to start flushing in around 130 years time.

Have you looked at the sandbars in the Kawarau arm lately... ??? I reckon in 50 years, water will flow over the Bannockburn bridge...Upstream of there its only safe for jet boats.

[Jantar]

Thats exactly what happens...

Fortunately, such dams do have a life expectancy... Roxburgh I think (Jantar may correct me) has passed its original period of expectancy. Even with upgrades, its still a 50 year old dam.

And downstream of the dam, they don't want the silt either... It tends to block the outlet of the river and cause flooding...

The plant has a design life of 30 - 40 years, which is why Roxburgh has recently gone through its 1st life refurbishment. ie all the stators have been replaced, rotor poles rewound and turbines reshaped. The dam does not have a fixed life expectancy. The concrete in that environment will last indefinitely.

Downstream of the dam some people do want the silt (spawing beds for fish) and others don't want it (orchidists don't want silt in their irrigation systems). But no, it doesn't block the river outlet. It is only carried during times of high flow, and deposited when flows are low.

[Jantar]

Have you looked at the sandbars in the Kawarau arm lately... ??? I reckon in 50 years, water will flow over the Bannockburn bridge...Upstream of there its only safe for jet boats.

Part of the water right when Clyde dam was built required the Crown to purchase all land upstream of the confluence of the Clutha and Kawarau rivers to height that the river is expected to rise to plus an allowance for floods. When Contact energy was formed this land was passed to Contact. The Kawerau from around the goldfields area to just below the Bannockburn arm will become a braided river just like the Waitaki. The tipping face of the silt was originally expected to reach the confluence 20 - 30 years after the dam started filling, then take another 100 - 150 years to reach the Basin imediately upstream of the Clyde Dam. Filling started 18 years ago, and the tipping face is now around 4 years from reaching the confluence. During those 18 years we have seen the 3 largest floods since records began, so those early engineers look to have got it right.

[Hitcher]

More lines of pylons and an AC-DC converter in the South, another Cook Strait cable and another Haywards in the North, and we may be able to get by with less thermal generation?

[Ixion]

Whereas an intelligent government would move industry south. Most industrial operatoions could run just as well (After a few adjustments) in the South Island as in Dorkland. They don't cos the bosses want to live in the big smoke. So, it becomes a proper part of the provenance of government to tell them to pack up and start moving. Or else.

And , of course, along with the industry go the workers. Or else.

I'd be packed within 24 hours, m'self.

[Jantar]

Whereas an intelligent government would move industry south. Most industrial operatoions could run just as well (After a few adjustments) in the South Island as in Dorkland. They don't cos the bosses want to live in the big smoke. So, it becomes a proper part of the provenance of government to tell them to pack up and start moving. Or else.

And , of course, along with the industry go the workers. Or else.

I'd be packed within 24 hours, m'self.

That is just too logical. As population moves away from Auckland, traffic congestion would disappear, so there'd be no justification for speding big money on new motorways, rail links etc. Demand for water would reduce, so the existing reservoirs would be adequate. ;)

[White trash]

Great photos Okey. Takes me back to my childhood of thrashing a trials bike all over North Otago and swimming in Lake Aviemore constantly during summer.

No better place on earth could a kid hope to grow up.

Also seems funny to me that this is the first spill in five years. When I was a kid, every Chrsitmas for about two weeks all three dams would be spilling full noise.

Most amazing thing to watch

[White trash]

Whereas an intelligent government would move industry south. Most industrial operatoions could run just as well (After a few adjustments) in the South Island as in Dorkland. They don't cos the bosses want to live in the big smoke. So, it becomes a proper part of the provenance of government to tell them to pack up and start moving. Or else.

And , of course, along with the industry go the workers. Or else.

I'd be packed within 24 hours, m'self.


Share a cab?

[Okey Dokey]

Hey, white trash, I'm glad you liked them. It's not something many NZers have seen and that is why I posted the pics.

Mind you, the state of the country's electricity infrastructure is also worthy of comment...I'm pleased so many have something to say about that, as well. We aren't in a good place, as a country, and I hope we can improve.

[Winston001]

Hey, white trash, I'm glad you liked them. It's not something many NZers have seen and that is why I posted the pics.

Mind you, the state of the country's electricity infrastructure is also worthy of comment...I'm pleased so many have something to say about that, as well. We aren't in a good place, as a country, and I hope we can improve.

Thanks for sharing OD and I too can remember watching a Benmore spill as a kid years ago.

As for our electricity infrastructure - that is a national disgrace. The lines are owned by the Government (Transpower) so no reason for them not to be upgraded. I suspect the fact that prices would have to rise is politically unacceptable. Plus the Electricity Commissioner has in his wisdom ruled the SI generators have to pay to send power across Cook Strait. Not much incentive for them to do that when spot prices are low. So they spill instead.

To add salt to our wounds, our neighbour, that well-known place of plentiful water and hydro-electricity :gob:, Australia has cheaper electricity than we do. How the hell can that be???

[Winston001]

Whereas an intelligent government would move industry south. Most industrial operatoions could run just as well (After a few adjustments) in the South Island as in Dorkland. They don't cos the bosses want to live in the big smoke. So, it becomes a proper part of the provenance of government to tell them to pack up and start moving. Or else.

And , of course, along with the industry go the workers. Or else.

I'd be packed within 24 hours, m'self.

You are speaking to the converted but I can't see it happening. Having lived in a far-flung province all of my life, my observation is the move to large cities by government departments, businesses, and manufacturers is a one-way process. Once there a culture of entitlement sets in and people simply refuse to move away. Including the decision makers.

I know a large forestry company which centralised in Auckland 5 years ago despite having most of their assets in the South Island. It made no sense to the SI staff but the Auckland branch simply refused a shift to Christchurch, and the overseas bosses stipulated Auckland - end of story. Go figure.

At times like this I'm sympathetic to your command economy Ixion, its just being too much of being a pale liberal for me to agree. :D

[Shadows]

Whereas an intelligent government would move industry south. Most industrial operatoions could run just as well (After a few adjustments) in the South Island as in Dorkland. They don't cos the bosses want to live in the big smoke. So, it becomes a proper part of the provenance of government to tell them to pack up and start moving. Or else.

And , of course, along with the industry go the workers. Or else.

I'd be packed within 24 hours, m'self.


That is just too logical. As population moves away from Auckland, traffic congestion would disappear, so there'd be no justification for speding big money on new motorways, rail links etc. Demand for water would reduce, so the existing reservoirs would be adequate. ;)

Fuck that. A little bit of global warming is a small price to pay to keep the JAFAs right where they are.

[gunrunner]

It will be interesting to see if we get low on power in the winter , and howcome they didnt let the local farmers draw the excess water from the lakes for irrigation as they will be in drought soon

[Trumpess]

... and howcome they didnt let the local farmers draw the excess water from the lakes for irrigation as they will be in drought soon


That was a thought I had aswell Gunnrunner.
Bit of a waste really!!

[imdying]

Jantar, can you still take the tour inside the Benmore dam?

[Ralph]

Yeah some good photo's alright, not often Benmore spills as you say so good on ya for taking the time to get them :niceone:

With the Tiwai smelter having a few issue's it has highlighted a couple of short falls in the transmission system which is a good thing, sure it would have been great if they knew about it before but shit happens.
And the DC link is in bad need of upgrades or replacemant so when we have this excess water the thermals can be shutdown.
My 2c :D

[k14]

Yeah the 200MW loss at Tiwai along with higher than previous year's inflows has contributed to the spilling. I think last week we were more than 2 standard deviations above average for NZ storage (so that is only a 2% or less of the time situation). But if pole 1 of the HVDC (which was put out of service in Sept 2007) was still in service there would be a marked less amount of spill in the SI. Don't be too alarmed though, we have just had the two weeks of the lowest demand NZ has in a year and it is fairly common for a few of the hydro dams to have a little bit of spill, even in lowish flows.


Great photos Okey. Takes me back to my childhood of thrashing a trials bike all over North Otago and swimming in Lake Aviemore constantly during summer.

No better place on earth could a kid hope to grow up.

Also seems funny to me that this is the first spill in five years. When I was a kid, every Chrsitmas for about two weeks all three dams would be spilling full noise.

Most amazing thing to watch
Yeah back then the demand was a lot less and we had a big excess on the supply side of things after the big development of the waitaki and clutha in the 60's-80's so spilling would have been a bit more common. Although in saying that, the whole electricity system was centrally controlled and totally state owned so in some areas would have been run more efficiently.

[klingon]

Wow, what an interesting thread this has become! Thanks for the photos Okey, and thanks to everyone else for your fascinating contributions.

I came to KB today expecting to see (and participate in) the usual rubbish, and instead I get educated on the state of hydro generation in NZ. Much more interesting!

[warewolf]

Whereas an intelligent government would move industry south. Most industrial operatoions could run just as well (After a few adjustments) in the South Island as in Dorkland. They don't cos the bosses want to live in the big smoke. So, it becomes a proper part of the provenance of government to tell them to pack up and start moving. Or else.I grew up in a place halfway between Sydney and Melbourne where they ran a decentralisation scheme in the 1970s. But it was slightly different; part of the gain was that being halfway was cheaper than being based in one and doing business in both.

As a kid I visited the power stations in the Snowy Mountains scheme often, sometimes with my engineer Dad when the last of them was being built. Feeling the water rushing through the huge pipes at Tumut 3 station is pretty amazing, as is the sheer power (ha ha) inside the generator building when it is really humming. I always wanted to go down into the bowels of the generators, but they wouldn't let me. :(

[Bass]

I always wanted to go down into the bowels of the generators, but they wouldn't let me. :(

I have walked a penstock at Aratiatia and stepped out through the governor blades onto the turbine runner.
It was an eerie feeling knowing that on the other side of that door was 40 million gallons of Lake Aratiatia. I really hoped that the sparkie had indeed pulled the fuses on the door drive.

[imdying]

I always wanted to go down into the bowels of the generators, but they wouldn't let me. :(When I was younger, maybe 15 years ago, I went through the Benmore dam, so close to the spinning shafts of the turbines you could reach out and touch them. Hopefully someone can tell us if you can still tour them, I'd ride down there for a day just to do that again. Impressive engineering yessssss :yes:

[FJRider]

While working in Manapouri a few years back. We were offered a trip across the lake to west arm power station(on the workers boat). Were given a tour through the whole thing. From the very bottom where we go a look inside a "snail shell" the water flows through, to drive the turbine.
They were doing maintaince on it, and was very scarey hearing the water flowing past in the next turbine. Standing on steel polished by water. We were taken up in the lift, right up to the control buildings.

[Winston001]

Yeah the 200MW loss at Tiwai along with higher than previous year's inflows has contributed to the spilling. I think last week we were more than 2 standard deviations above average for NZ storage (so that is only a 2% or less of the time situation). But if pole 1 of the HVDC (which was put out of service in Sept 2007) was still in service there would be a marked less amount of spill in the SI. Don't be too alarmed though, we have just had the two weeks of the lowest demand NZ has in a year and it is fairly common for a few of the hydro dams to have a little bit of spill, even in lowish flows.


Yeah back then the demand was a lot less and we had a big excess on the supply side of things after the big development of the waitaki and clutha in the 60's-80's so spilling would have been a bit more common. Although in saying that, the whole electricity system was centrally controlled and totally state owned so in some areas would have been run more efficiently.

I still believe that NZ is too small to have competitive businesses producing electricity. Max Bradford was wrong. Central longterm planning by Government is best. But what is done is done.

Having said that, Meridian, Mighty River Power, and Genesis are all government owned. So is Transpower. So the government has the ability to direct these SOEs to do what it wants.

Unfortunately governments are gutless. Upgrading the transmission network requires money which means power price increases - and that's politically unacceptable. However government could commit taxation money to this work. Instead we've had 9 years of social engineering while basic infrastructure slowly crumbled. :Oi:

[Okey Dokey]

When I was younger, maybe 15 years ago, I went through the Benmore dam, so close to the spinning shafts of the turbines you could reach out and touch them. Hopefully someone can tell us if you can still tour them, I'd ride down there for a day just to do that again. Impressive engineering yessssss :yes:

According to this site: www.meridianenergy.co.nz , there are daily tours during the summer at 11am, 1pm and 3pm. You may want to email them to confirm this before you head out.

[Badjelly]

Unfortunately governments are gutless. Upgrading the transmission network requires money which means power price increases - and that's politically unacceptable. However government could commit taxation money to this work. Instead we've had 9 years of social engineering while basic infrastructure slowly crumbled.

I'm just waiting for all the libertarians who frequent this site to tell you how wrong you are. :jerry:

[imdying]

According to this site: www.meridianenergy.co.nz , there are daily tours during the summer at 11am, 1pm and 3pm. You may want to email them to confirm this before you head out.Thanks a lot :yes:

[Okey Dokey]

Happy to help.

[Ocean1]

I'm just waiting for all the libertarians who frequent this site to tell you how wrong you are. :jerry:

Libertarians aren't agin' government, dude. That'd be anarchists. Most libertarians would, I reckon, recognise a government's valid roll in funding and planning supply for that sort of infrastructure.

Or the more rational ones would.

Personally, I believe the function of the above SOEs is to insulate govt from both funding and supply pressures. Fact is the sheer size of a workable long term "best practice" generation infrastructure budget was seen as a formidable impediment to the far more important busines of buying votes THIS year.

The fuckers bought us off with a threepenny bag of lollies, and now they're all gorne.

[FJRider]

Personally, I believe the function of the above SOEs is to insulate govt from both funding and supply pressures. Fact is the sheer size of a workable long term "best practice" generation infrastructure budget was seen as a formidable impediment to the far more important busines of buying votes THIS year.



I believed the function of SOE's was to be stand-alone money making businesses for the goverment. If they cant make a profit... they're sold off for a couple of big bags of lollies...
Previous Goverments seem to have believed that money for upgrades to these SOE's, from taxation, would leave money for other area's short. Plus cut into/out, any possible profit in the process.
The big impediment to any new power generating schemes is the ability, after the scheme's are built... to get the power to where its needed. Upgrade costs for transmission lines, have to be built into build costs for any new scheme.
Someone has to pay... no prizes for guessing who will end up paying... one way or another. :blank:

[Ocean1]

I believed...

Sorta wot I said.

A market purist would observe that, a): a public institution is inefficient in terms of core product delivery, and b): an entity constrained by actual market forces is the answer.

It's only the answer, however, if the market is open to competition, supposedly the reason the NZED was replaced by multiple "commercial" entities.

It's bullshit, of course. "Customers" have little real choice in terms of who they source their power from.

Dem other fellas might point to all the extras a genuine public service provide. Training, research economies of scale etc. And they'd be right. I figure the line should be drawn at some sort of erstwhile rest home/recreation club like NZR, MOW, NZED etc became, though.

So. How do you sort things so's you've got the best of both worlds, eh?

[Hitcher]

The original rationale for SOEs was to put the state's commercial assets into units that could, in the fullness of time, be sold. Some were. More would have been. One has been bought back again.

There are a couple I would sell, if I were in a position to do so. One is Solid Energy (the state-owned coal mining company) and the other is TVNZ.

I would sell Solid Energy because it cops so much flack for being a state-owned environmental villain (which it isn't) and I'd sell TVNZ (and RNZ for that matter as well) because I don't believe that the state should have any legitimate role in broadcasting. The government doesn't own newspapers. Radio and TV are no different.

I don't think that privately owned utility companies are a smart move in a country like New Zealand, and the SOE model is probably about the best way of managing these.

[jrandom]

... I don't believe that the state should have any legitimate role in broadcasting.

I do.

RNZ runs many programmes that improve the mind and enrich the social fabric of the nation and wouldn't be touched with a barge pole by commercial broadcasters because the audience isn't easily advertisable-to.

That not-for-profit focus should be strengthened and continued. That's the legitimate role of state-sponsored broadcasting.

[Ocean1]

Stop being so fucking reasonable.

How can a man have a cathartic wee rant if some bastard chucks a bucket of cold facts all over the place.

[Ocean1]

I do.

You've been drinking with Les agin' haven't you.



RNZ runs many programmes that improve the mind and enrich the social fabric of the nation and wouldn't be touched with a barge pole by commercial broadcasters because the audience isn't easily advertisable-to.

The enrichment isn't working. I don't need or want to be advertised at by anyone who can't anti-up the cost of the ad's.

[Hitcher]

That not-for-profit focus should be strengthened and continued. That's the legitimate role of state-sponsored broadcasting.

That's only one step away from propaganda. Given another term in office, I am sure the Bloody Labour Gummint would have turned its attention to the content of state-owned broadcasters.

TV3 broadcasts informative documentaries like Outrageous Fortune that enrich our social fabric, whereas the state broadcaster stoops to sodomy on Shortland Street to titillate and seduce advertisers.

[jrandom]

That's only one step away from propaganda.

Piffle.

The other weekend (and by 'other weekend', I mean 'quite a while ago', but the point still stands), out for a ride on the pushbike, I switched my MP3 player to National Radio and was pleasantly surprised to find myself listening to an interview with Michael Chabon. (It so happened that I'd just finished reading Kavalier & Clay.)

I can't think of any other NZ radio stations that would ever licence such stuff off the American public broadcasters. 'Propaganda'? Nonsense.

I challenge you to name one single programme on RNZ that counts as 'propaganda'.

[Winston001]

I do.

RNZ runs many programmes that improve the mind and enrich the social fabric of the nation and wouldn't be touched with a barge pole by commercial broadcasters because the audience isn't easily advertisable-to.

That not-for-profit focus should be strengthened and continued. That's the legitimate role of state-sponsored broadcasting.

In the USA, the best television can be seen on Public Broadcast Service (PBS) stations. PBS is a charitable company and only exists through donations and whatever support it can get. Essentially it does what the BBC1 and TVNZ do. We are lucky - although for a while Prime TV were broadcasting much better stuff than TVNZ.

I too support non-profit radio and television. TVNZ needs a separate channel for this stuff so it can legitimately concentrate on profit for its other channels.

[Bullitt]

Libertarians aren't agin' government, dude. That'd be anarchists. Most libertarians would, I reckon, recognise a government's valid roll in funding and planning supply for that sort of infrastructure.

Or the more rational ones would.


Umm not quite. Theres a reason only something like 1,000 people vote for Libiterianz each election. Id say Im in the top 5-10% of right wing people in NZ but I dont go anywhere near their policies.

Libertarians basically believe the only role for the state is in services that will never be provided by the market such as armed forces and um thats about it. No Libertarian would ever go near electricity.

[Ixion]

That's only one step away from propaganda. Given another term in office, I am sure the Bloody Labour Gummint would have turned its attention to the content of state-owned broadcasters.

TV3 broadcasts informative documentaries like Outrageous Fortune that enrich our social fabric, whereas the state broadcaster stoops to sodomy on Shortland Street to titillate and seduce advertisers.

The BBC, in its glory days., was undoubtedly the most respected broadcaster in the world. And government 'controlled'. The only propaganda it put out was during the two world wars .

To say that the state should have no role in broadcasting is as meaningless as to say it should have no role in education.

If a state controlled braodcaster braodcasts government propaganda, how is that any worse than a capitalist controlled braodcaster broadcasting Business Round table propaganda? At least the state must take account of all citizens when formulating its propaganda, whereas the privately operated broadcaster will take account only of the wishes of the rich capitalists who control it.

[Winston001]

Never mind the OT stuff - someone tell me why our transmission lines have been allowed to deteriorate. I've read about this stuff and it's very confusing. One expert says we need a second Cook Strait cable and some clever transformer stuff, another says no worries, there's still years of use in what we have. They go on to claim the generating companies are trying to yield super profits with alarmist statements about the lines. How that works I do not know.

[FJRider]

Stop being so fucking reasonable.

How can a man have a cathartic wee rant if some bastard chucks a bucket of cold facts all over the place.

Don't let a bucket of cold facts stand in the way of a good cathartic wee rant... :rockon:

[McJim]

Never mind the OT stuff - someone tell me why our transmission lines have been allowed to deteriorate. I've read about this stuff and it's very confusing. One expert says we need a second Cook Strait cable and some clever transformer stuff, another says no worries, there's still years of use in what we have. They go on to claim the generating companies are trying to yield super profits with alarmist statements about the lines. How that works I do not know.

It's not supposed to work. One has a vested interest in an additional power line and transformer thingumy and the other has a vested interest in the status quo. Facts really have no place in NZ politics :rofl:

[Winston001]

It's not supposed to work. One has a vested interest in an additional power line and transformer thingumy and the other has a vested interest in the status quo. Facts really have no place in NZ politics :rofl:

This wisdom from ae Scotsman..... You lot are all engineers - why dontcha fix it!! :blink:

[98tls]

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[98tls]

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[98tls]

Took a few pics of the spill today,called into Chez Oldrider for camera lessons (thanks John) and received a warm welcome complete with lovely sammies (thanks Pip).

[Zippity]

There used to be a huge island out in the middle of the river, right in the path of the water that was discharged from the spillway - alas, it was washed away several years ago :(

I often walked across the ledge at the bottom of the spillway in pursuit of the monster trout that lived down below the concrete walls there :)

[oldrider]

There used to be a huge island out in the middle of the river, right in the path of the water that was discharged from the spillway - alas, it was washed away several years ago :(

I often walked across the ledge at the bottom of the spillway in pursuit of the monster trout that lived down below the concrete walls there :)

That rock was blown out when the gates were first tested at full (60,000 cubic feet per second) discharge. :yes: John.

[vifferman]

The media said the latest spilling was to attempt to blow dydimo out of the river. Sounds like bollix to me - is it just someone trying to put positive spin on this, or is there some partial truth in that they made the discharge extra big in the hope it would help with the dydimo thing?

[Jantar]

Meridian's lakes are all over their maximum operating level, so spill is mandatory. As they have to spill anyway, it is obviously an ideal chance to see if flushing will reduce the amount of didymo.

Contact will possibly do something similar (but not as spectacular) in the Hawea river next month.

[Zippity]

The media said the latest spilling was to attempt to blow dydimo out of the river. Sounds like bollix to me

Must admit I laughed when I heard that "ill-informed" comment on TVOne news last night :(

Lake Aviemore is about 400 yards downstream of the spillway, then there is Lake Waitaki, before the river proper starts at its base - and that is just a couple of clicks upstream from Kurow :)

Once again another poor example of the "hand-out" journalism that is practised here in New Zealand. Maybe if the reporter got off his arse and went and saw for himself, we might have had a half decent story.

[Jantar]

Must admit I laughed when I heard that "ill-informed" comment on TVOne news last night :(

Lake Aviemore is about 400 yards downstream of the spillway, then there is Lake Waitaki, before the river proper starts at its base - and that is just a couple of clicks upstream from Kurow :)

Once again another poor example of the "hand-out" journalism that is practised here in New Zealand. Maybe if the reporter got off his arse and went and saw for himself, we might have had a half decent story.

It isn't possible to pass 960 cumecs through Benmore without it also going through Aviemore and Waitaki. With the tributaries coming in along the way its 1000 cumecs flowing down the river.

So where is that "ill-informed" comment"? :whistle:

[Zippity]

To "flush out the river" as the reporter said, huge quantities of water must first be released into the river.

The Aviemore Dam (like Benmore) has a spillway also, Waitaki doesn't.

Waitaki relies on gravity to shed it's excess water - ie, once the lake is full, it flows over the top of the dam.

I'm not aware of this happening at this stage :(

[Jantar]

To "flush out the river" as the reporter said, huge quantities of water must first be released into the river.

The Aviemore Dam (like Benmore) has a spillway also, Waitaki doesn't.

Waitaki relies on gravity to shed it's excess water - ie, once the lake is full, it flows over the top of the dam.

I'm not aware of this happening at this stage :(

Waitaki is a weir type dam, so yes, water does flow over the top. It has been doing that for some weeks now.

If it wasn't happening then where is the water from Benmore going? As Lake Waitaki surface area is only around 5 km^2 then 1000 cumec inflow would cause the level to rise 1 mm every 5 seconds. That is 0.72 m per hour or 17 m per day. What is this new magic water storage system that Meridan have discovered that allows this amount of water to be stored in a small lake? :lol:

[Bass]

So where is that "ill-informed" comment"? :whistle:

Well I'll admit to being ill informed, but doesn't he have a point?
I presume the hydro lakes will remain close to full during this process and therefore (I would guess) the current speed through the lakes is unlikely to be high enough to clear out didymo. On top of that, you mentioned Hawea as yet to happen.
If they were trying to flush didymo, would it not make sense to start as far upstream as possible and work downstream from there?
(Genuine questions BTW)

[Okey Dokey]

Great to see the new photos- they are impressive. The water flow in the Waitaki is phenomenal at the moment- also very impressive.

As well as possibly reducing the didymo levels, even temporarily, I heard that a nice clean river bed will be good for the salmon spawning later, too.

[k14]

Well I'll admit to being ill informed, but doesn't he have a point?
I presume the hydro lakes will remain close to full during this process and therefore (I would guess) the current speed through the lakes is unlikely to be high enough to clear out didymo. On top of that, you mentioned Hawea as yet to happen.
If they were trying to flush didymo, would it not make sense to start as far upstream as possible and work downstream from there?
(Genuine questions BTW)
Didymo doesn't grow in lakes, only in fast flowing rivers. The flush (using water originally from lake tekapo and pukaki) will flush all the way from benmore, through aviemore and waitaki and then down the waitaki river out to sea. I'd hazard a guess that most of the didymo is growing downstream of the waitaki dam and thus the 1000+ cumecs running down through there will do a good job at washing it away!

[Jantar]

.... On top of that, you mentioned Hawea as yet to happen.
If they were trying to flush didymo, would it not make sense to start as far upstream as possible and work downstream from there?
(Genuine questions BTW) Hawea is on a totally different river system from the Waitaki. Meridian are starting as far upstream as possible by releasing water from Tekapo and Pukaki directly into Benmore, then down the river chain of Aviemore and Waitaki into the Waitaki river.

Hawea is currently releasing 30 cumecs, and that is likely to increase to 200 cumecs in late february.

[Bass]

Didymo doesn't grow in lakes, only in fast flowing rivers. The flush (using water originally from lake tekapo and pukaki) will flush all the way from benmore, through aviemore and waitaki and then down the waitaki river out to sea. I'd hazard a guess that most of the didymo is growing downstream of the waitaki dam and thus the 1000+ cumecs running down through there will do a good job at washing it away!

Downstream of the Waitaki I have some optimism about - 1000 cumecs is no small trickle - but the rest of it I'm not so sure about. I know we are only talking about a bit of a clean out here and that eradication is probably impossible. So perhaps you're right. I'll keep my fingures crossed


Hawea is on a totally different river system from the Waitaki.
Doh!! Marbles disappearing rapidly.


Meridian are starting as far upstream as possible by releasing water from Tekapo and Pukaki directly into Benmore, then down the river chain of Aviemore and Waitaki into the Waitaki river.

Hawea is currently releasing 30 cumecs, and that is likely to increase to 200 cumecs in late february.

Thanks for that. What's the extent of the didymo problem in the Clutha?

[Zippity]

Man I so much want to go back down to the Waitaki Hydro system for some fishing :)

There is nowhere like it on earth :D

[Jantar]

..... What's the extent of the didymo problem in the Clutha?

Its quite bad in the Hawea river, and getting worse in the upper Clutha. The lower Clutha is quite deep and slower moving so not too much of an issue there.

[Forest]

I still believe that NZ is too small to have competitive businesses producing electricity. Max Bradford was wrong. Central longterm planning by Government is best. But what is done is done.

Having said that, Meridian, Mighty River Power, and Genesis are all government owned. So is Transpower. So the government has the ability to direct these SOEs to do what it wants.

Unfortunately governments are gutless. Upgrading the transmission network requires money which means power price increases - and that's politically unacceptable. However government could commit taxation money to this work. Instead we've had 9 years of social engineering while basic infrastructure slowly crumbled. :Oi:

It isn't quite that simple. Just look at the Waikato Transmission Line project.

The last government committed $500 million to run new transmission lines into Auckland, but the Waikato farming community has managed to hold the country to ransom by stalling the project.

[oldrider]

It isn't quite that simple. Just look at the Waikato Transmission Line project.

The last government committed $500 million to run new transmission lines into Auckland, but the Waikato farming community has managed to hold the country to ransom by stalling the project.

That's referred to as the NIMBY syndrome. IE: "Not In My Back Yard". :doh:

It's everywhere in New Zealand! :rolleyes:

Give me the electricity but not the infrastructure! :headbang: John.