Wivenhoe Dam Levels – The Critical Days

Posted on Thu 01/20/2011 by

2


UPDATE. (February 2016) This Post was originally done in 2011, immediately following the major flood event. Since that time, the link for the images for SEQWater has changed. This is the new link to that site and the images can be accessed at the bottom of the text at that link, and you just tick the boxes in question at the right of the interactive chart there, and for the Wivenhoe and Somerset Dams, just untick the top default box, Grid 12, and then tick the boxes for those two dams, near the bottom either together or individually, and then navigate for time periods using the tab buttons for dates under the main screen there, and you can hover your mouse over the dates in question for dam levels.

THREE MAJOR UPDATES ARE AT THE BOTTOM OF THIS POST

This is a necessarily long Post. The information needs to be kept in this one Post, and not split into two or even three Posts.

So that this Post could just concentrate on the levels of Wivenhoe Dam prior to the flood in January 2011, I have not included any background as part of this Post. That background is in two separate Posts at the following links. That background is of interest in the context of this Post, and they should be looked at to gain insight into that background. The links to those two Posts are as follows.

1. Wivenhoe Dam Levels – Background – Before the 1974 Flood

2. Wivenhoe Dam Levels – Background – After the 1974 Flood

What needs to be at the forefront of everyone’s minds here is that the word to have the most stress placed upon it is Mitigation.

People will confuse this with the word Prevention.

Wivenhoe Dam’s main purpose, other than supplying a large water supply for South East Queensland, is to mitigate major floods, not to prevent them from causing flooding, but to lessen the effects of any major flooding event.

Did Wivenhoe Prevent the flood?

No.

Did Wivenhoe lessen the effects of that flood with its flood mitigation compartments?

Yes, considerably so, in fact saving Brisbane from a disaster a quantum level worse than the disastrous floods of 1974?

However, having said that, could that mitigation have been handled a little better to even further lessen what did happen.

That will be the subject of long debate, and in fact will all come out into the Royal Commission of Inquiry that has been set up by the Bligh Government here in the State of Queensland.

What I will show here is in no way an answer to that debate, but just a set of facts supported by images, showing those dam levels over the critical days leading up to and including the flood, and a time line of what happened.

These images are taken from the Government site SEQWater, and that site is at this link, and for a better understanding, it requires some explanation.

Scroll to the bottom of the page at that link and you will see a chart. That chart is interactive and shows the dam levels and the levels for the total water holdings for South East Queensland. The current default setting is for Grid three as you can see with that box at right ticked.

Under the chart is a smaller chart. At the right of that chart is a small interactive box that can be moved to show any time frame, be it small or large. What is contained in the area inside that box is what is indicated in the main chart above.

Then, on that main chart you can hover your mouse over the line and see the individual capacities on a particular date.

Now to get the data for Wivenhoe Dam on that chart, and only for Wivenhoe Dam, you need to tick the box alongside that for Wivenhoe Dam, and then untick the box for Grid Three. What you see now is the data in that main chart just for Wivenhoe Dam alone, and you can then hover your mouse over that line to see the levels for Wivenhoe for each day.

The same applies for the figures for Somerset Dam, which you would need to tick for its figures to show in that main chart.

Now, so you don’t have to refer back and forth to that link while reading this text, I have taken screen images for the days in question. with the mouse hovering over the percentage figure for that day.

With every image at this page, if you click on it, the image will open in a new and larger page for greater detail.

Friday 7th January 2011.

So, to better explain it, these first two images show the levels for both Somerset (top) and Wivenhoe (lower) Dams just prior to the huge rain event beginning. What needs to be remembered here is that Somerset Dam is directly up stream of Wivenhoe, and any releases from Somerset flow directly into Wivenhoe.

You can see a couple of smaller spikes prior to this date where Wivenhoe filled beyond 100% and water was then released from those flood mitigation compartments to get the level back down to 100%, as they are required to do.

The images show the levels for Somerset at 107.2% and  Wivenhoe at 106.3%, and this is for Friday 7th January, shown in the highlighted text box over that small dot on the line for that day.

The gates at both dams were open and water was being released into the river, but at a controlled and lower rate, releasing water that was in the flood mitigation compartments that was still building up from inflow into both catchments from those recent rain events.

What is a little odd here is that both levels are up over 100%, which means that the Dam operators for both dams should be increasing discharges form the dams at a higher rate to empty the flood compartments and restore both dam levels to a percentage at or around 100%. What also needs to be considered here is that dam operators had received advice from the Bureau of Meteorology that the weather report for the next few days showed that there would be significant rainfall. In fact, this was not advice given just to the dam operators, but was broadcast over most of the news bulletin weather reports on TV and radio.

***

What happens from now on starts to get intense, and needs some very careful reading for the sequencing of a time line for the events.

Monday 10th January 2011.

These two images show the levels for the next reporting day, 9AM Monday 10th January.

Now, don’t be alarmed by the fact that there was no reporting on the two days of the weekend. There never has been over all the years.

This does not mean everyone has just packed up and gone home for the weekend. All this means is that the person who is tasked with updating the SEQWater website is most probably someone from the clerical side of the operations, and that admin area just works on the Monday to Friday basis.

As you can see from the images, the level for Somerset is at 154.7% and Wivenhoe is at 148.4%. Both dams now have their flood mitigation compartments filling rapidly, still from inflows into both catchments. Gates were open and water discharging from both dams over the weekend, but at the lower rate of discharge. Come that Monday morning and the calculators would have been running hot with both dams now significantly higher, with water filling those flood mitigation compartments, and now needing to be discharged to lower them back to the required 100%.

On that Monday, there was a significant rain event in both Toowoomba and in the Lockyer Valley.

It’s worthwhile keeping in mind that a Government department like this is hamstrung by bureaucracy and that any decisions after they are worked through (which takes some time for something like this) would then have to be passed up the reporting change before any decision to increase major outflows from Wivenhoe are approved.

At some time late on Monday or early Tuesday morning, the gates at Wivenhoe were opened so that water flowed from them at the rate of 645,000 Megalitres (ML) per day. That does not mean that much water was released, but that the water flowing from it would have amounted to that 645,000 ML if it was kept up for the full 24 hour period. Water was now flowing into Somerset and Wivenhoe at a rate greater than they were releasing it, so that rate of the 645,000 ML just had to be sustained. This huge amount of water flowing directly into the River took 36 hours to reach Brisbane, and this is what caused that initial flood peak to rise. This rate of release also needed to be carried out at that time, because (a) water was flowing in faster than they could release it, and (b) also early so that any further release at such a large rate would not be exacerbated by the King tides expected on Thursday and Friday Mornings. Those king tides would slow river inflow into Moreton Bay and the ocean and water in the river would ‘back up’ causing increased flooding.

Now, keep in mind that Wivenhoe can effectively hold 230% of its capacity, so some might even say that the release need not have been done because there was still percentage to play with. However, having said that, this is what effectively amounts to an incredible juggling act, and, as no one can calculate what might happen in the future, that huge release rate had to be done, and it had to be done on the Monday.

***

Sometime on Monday night, that rain dump became considerably worse, and this huge rain event hovered over the area of both dams and their catchments well into the following day, Tuesday. I watched that rain event on the Bureau of Meteorology weather site on the Mt Stapylton Doppler Weather Radar set to 128 Km on and off throughout the day, and the heavy areas indicted by yellow colours through to red persisted in that area for the 12 hours I was watching, that rain just sitting directly over the top of this and large surrounding areas.

Tuesday 11th January 2011.

These next two images show the levels taken as at 9 AM Tuesday morning 11th January.

Somerset Dam at is 160.8% and Wivenhoe Dam is at 175.9%.

This date and time is very important for a number of reasons.

At 9 AM on that Tuesday morning, the 11th January, the dam levels page was updated, not to show the percentages, but just the total holdings in ML of the two main dams in question. That level on that date was then not changed until the 13th, the Thursday. However, the Home page was updated in that one small section that showed the release information from Wivenhoe. On that Tuesday, it showed the release figure of 645,000 ML per day.

This figure could be better explained.

That is a rate of release only. If they kept up that rate of release for the full 24 hours, then 645,000 ML would be released. As this Tuesday Morning home page update reflected what happened on the Monday, then that release was on the Monday, probably late in the day or into the early evening, and this water took 36 hours to flow down the river and into Brisbane, and the flooding started in the Capital.

***

Wednesday 12th January 2011.

These two images show the levels for Somerset and Wivenhoe for the day after the huge dump of rain in that area.

As I mentioned in the section for Tuesday, the dam levels page at the SEQWater site was not updated, so it was well after the fact, when these percentage levels were updated at that page that I took these screen shot images for those two days in question when the dam level figures were not updated.

They show the level for Somerset at 189.7% and the level for Wivenhoe at 188.5%.

The immense juggling act which started sometime on the Monday was now becoming pretty intense would be my guess. You have a level for Somerset getting huge, Wivenhoe also getting huge, even if it can still get to 230%.

Behind Somerset Dam, its catchment, already soaked was getting major inlows from the Stanley River, now in major flood, the upper Brisbane River, also in major flood,and all the other streams and tributaries as well. All of that backing up behind Somerset Dam, is released into Wivenhoe downstream.

What is flowing into Wivenhoe is still more than they are releasing. Then there is the amount of water to be releasing from Wivenhoe, and just how much that will add to the already rising flood in Brisbane, with a King tide expected in the early hours of Thursday morning.

Ipswich was also having major problems as well. The Bremer River was also in flood, and rising quickly as well. It flows into the Brisbane River at Riverview. It was backing up into Ipswich, and that city was in the grip of a disaster that started on the Tuesday and got even worse on this Wednesday, because its water could not escape into the Brisbane, already ‘chockers’ from what was coming down from Wivenhoe. Add this Bremer problem to what was already happening at Wivenhoe because that water in the Bremer was also adding to the disaster in Brisbane, and Wivenhoe control central had no control over what was happening in the Bremer. All Wivenhoe control could do was to adjust release rates to take what was happening in the Bremer into consideration.

While the dam levels page was not updated, the Home page was, if only for that one sentence. That release level for Wivenhoe for the previous day was replaced with one that said the release was reduced to 310,000 ML, again further accentuating the intense juggling act that was now in progress.

***

Thursday 13th January 2011.

By Thursday morning, the peak had passed with the advent of the King tide, and the level did not reach the expected height, and in fact was lower than the 1974 level. The disaster however was way more comprehensive that it was in 1974 because Brisbane was now a very much larger city. The juggling act at Wivenhoe was still as intense though.

These two images for Thursday 13th January show the level for Somerset at 171.4% and Wivenhoe at 186.5%.

Although the dam level page was not updated, the home page showed the release rate from Wivenhoe was lowered again to around 215,000 ML per day, and remember, that is only a rate of release. Even though Wivenhoe was now at such a high level, it was known that it could get to around 230%, so while that level is at that 186.5%, there is still a lot of water that can be still stored in those flood mitigation compartments. Somerset was holding steady, while still releasing at around the same rate as what was flowing into it from its still saturated catchment area. All that release from Somerset was flowing directly into Wivenhoe. In effect the best thing was probably now happening. Somerset was falling, and Wivenhoe holding steady, and still with room to hold more.

Brisbane had the worst of it on the Wednesday through to the Friday, and already some questions were being asked about the role played by Wivenhoe Dam in this now catastrophic flood event. That comment was mainly from people who had no real idea of what actually might have been happening, in the main, people who were confusing the word prevent with the word mitigation, and that is not said in an offhand manner to belittle that thinking, but complacency over the years with no major floods to ‘test’ Wivenhoe probably added to that thinking.

***

Friday 14th January 2011.

The dam levels page was updated at 9 AM, but only with those water level figures expressed in ML. The Home page was also updated saying that rate of release was still around that 215,000 ML rate but was going to be increased to 310,000 rate to empty the flood compartments to get the huge dam back down to 100% as they are required to do.

These two images are for 9 AM on that Friday 14th January.

They show Somerset back to 147.3%, well off its maximum, and Wivenhoe still ‘up there’ at 179%.

Somerset was releasing its flood compartments straight into Wivenhoe, so even while Wivenhoe was releasing at that increased rate, its level was still quite high, again accentuating the delicate juggling act required in a situation as dire as this one was.

Keep in mind the great number of factors that needed to be taken into consideration here.

It’s going to be very easy, ‘after the fact’ to dissect things from a lay point of view, but those engineers doing all this would have been working flat out, and around the clock, now for almost five days on the trot, because this was something you just could not take your eyes away from.

***

Monday 17th January 2011.

The next set of images are for the Monday, remembering that the person tasked with updating the web site is the person who went home for the weekend, and not all the engineers who would have still been hard at it.

Here I will just show three images, the two on Monday, that of Somerset, now back to 100.7% and Wivenhoe, down to 122.8, and the third image for Tuesday 18th January with Wivenhoe now back to 106.4%.

What is happening here is that Somerset has now drained all the water from its flood mitigation compartments. All that water has flowed directly into Wivenhoe, which is also emptying its flood compartments as well.

All this water is being released into the Brisbane river, still in flood, but now decreasing.

The water in the Bremer is also now getting away as well.

The disaster in Brisbane is now getting well into the clean up stage.

All eyes however are now looking back up the river directly at Wivenhoe.

***

CONCLUSIONS FROM A LAY PERSPECTIVE.

This was a juggling act of immense proportion that no one will understand, ever. Whatever findings are made as a result of the Commission of Inquiry, there will be people calling it a cover up. Some will say the Dam did its job, and others will say it failed its job miserably.

Some will thank Joh Bjelke Petersen from the bottom of their hearts, and others will condemn him with great vigour, although I dare say, no current politicians from the Labor Government will be thanking Joh, even grudgingly. They will want to see him still painted as the villain in all this, as he has been for decades now.

So having said this was a juggling act of the greatest proportion, some can look at the figures for Wivenhoe and say that it never even got close to that 230% maximum holding, so it could have held back even more water than it did.

However, consider what was flowing out of Wivenhoe, and what was flowing in from its own catchment and also from Somerset.

Water in – Water out. How much do you hold and when do you let it go?

Let’s say they hold back as much as they can and get close to that 230% mark. If it still keeps filling, then they would have had to let out an immense amount of water in one huge hit, which would have been even more devastating than it was.

Those release levels on the days of release were controlled well enough to lessen the impact of a monster release in one huge hit. which would have caused devastation on an unimaginable scale.

However, having said that, there is one glaring question. The problem was always going to be that king tide in the early AM hours of the Thursday. That huge dump of that 645,000 ML was at some time late on the Monday or early Tuesday morning, and that took 36 hours to reach the City, well before that King tide.

Now look at the rising level on the Friday prior to the huge rain event when Both Somerset were both at around 106% and rising steeply, and by the Monday Morning . Both dams were at or around 150% and rising, with the expected and warned of huge rain event still to kick in. There was no wriggle room now, and that huge rate of release was carried out.

Should the earlier rate of release on the Friday with levels rising, (and no fore knowledge of the coming dump) been increased even slightly so that the huge release on the Monday would not have to have been so great, and that rate of release then continued into the weekend.

That is about the only real major question I can see that needs answering.

Just what did happen on that Saturday and Sunday?

Was it just bad luck that the huge rain dump started on Monday (immediately after the weekend) and then got worse on the Tuesday, because with the dams already at around 150% prior to the huge rain event, then drastic measures needed to be taken on that Monday.

We’ll find out during the Commission of Inquiry, but in fact, from my lay opinion those guys did a great job.

So, we go right back to the top of the page.

Did that monster Wivenhoe Dam prevent this flood?

No.

Did Wivenhoe mitigate the effects of this flood?

Yes, and that is a solid yes. This rain event was comprehensively larger than the 1974 dump which caused that major flood, and while this flood caused more damage because Brisbane has morphed into a much larger city, the levels did not reach the same as they did in 1974.

To that end, Wivenhoe did exactly what it was supposed to do. This was its first major test, and it passed.

It didn’t get a Distinction, maybe a Credit, but it did what it was designed to do.

It mitigated the effects of a major major flood.

Nothing was going to prevent a flood that rain dump would have caused.

There are questions true, but they will be answered.

If I am allowed one extra wry comment here, thank heavens Joh Bjelke Petersen built this monster dam when he did.

Had they tried to do something like this in this day and age, the Greens Party would see to it that it never even got past the thought bubble stage. See how much The Greens Party think of human beings. They couldn’t care less. In fact, it would have given them more to rail about Climate Change on, and Bob, you’ve already started on that haven’t you?

UPDATE

How much water went into the Brisbane River just from Wivenhoe?

Consider this.

Wivenhoe Dam has the capability to hold around 230% of its capacity.

That extra water held back in its flood mitigation compartments amounts to 1.4 Million ML.

Now, let’s look at those releases from Wivenhoe. Here, there’s no need to look at releases from Somerset, as those Somerset releases flow directly into Wivenhoe.

At some time on the Monday, Wivenhoe released at the rate of 645,000 ML. Let’s pretend that amount was actually sustained for the full 24 hours resulting in that amount going into the river.

On the Tuesday, that release was lowered to 310,000 ML, and this rate was maintained for 2 days, hence a total of 620,000 ML.

The rate was then lowered to 215,000 ML and this was maintained for two days, hence 430,000 ML.

The rate was then increased back to 310,000 ML, and this was maintained until the flood compartments were emptied, for around four days hence a total of 1.24 Million ML.

Add all those totals together, and you arrive at a figure of almost 3 million ML, released into the Brisbane River to flow down and through Brisbane.

This is over and above the maximum flood mitigation holdings of 1.4 Million ML, in fact more than double the maximum flood mitigation holdings capability alone, so there was just no way Wivenhoe could hold back that much water.

That extra amount of water over and above the 230% amounts to 1.6 Million ML, which is almost three times the amount released on the Monday of that 645,000ML which took the 36 hours to flow down and into Brisbane, which caused the major flooding event there.

So, no matter which way you look at it, that vast amount of water had to be released into the river.

The juggling act is based around the release dates and when that water does get to the stage where it has to be released.

You cannot just extrapolate the maximum figure released here back down the calendar and divide that by the number of days to give a controlled average release, because during the huge rain dump, it fill faster than tt can be released.

So, looking at dam levels is an exercise worthy of doing, but it needs to be kept in the context of those releases, and when those releases need to be carried out.

UPDATE 2

The effect of the Bremer.

Consider the amount of water that was released into the river and flowed through Brisbane just from what was released from Wivenhoe.

It amounts to an extra 1.5 Wivenhoe’s over and above what Wivenhoe was holding back behind it, even with its flood mitigation compartments full. Here we have an amount of water equal to almost 3 full Wivenhoes when you consider what Wivenhoe was holding back, so that monster dam was NEVER going to hold back that much water.

Add to that what also had to flow trough the city of Brisbane was all the water from the Bremer River which was also in major flood, and was downstream of Wivenhoe. This was a significantly large amount of water over and above what was being released from Wivenhoe, and with all other steams and tributaries below Wivenhoe all in flood, then this water all had to flow through Brisbane.

When that huge release of water from Wivenhoe reached Riverview, where the Bremer River flows into the Brisbane River, that made it significantly more difficult for the Bremer to drain away. That’s not to say that Wivenhoe caused the major flooding in Ipswich, because the amount of water in the Bremer would have caused major flooding in Ipswich anyway.

Now perhaps you can get some sort of idea what the scale of the juggling act at Wivenhoe really was.

While people will obviously seek to lay blame, the biggest and most obvious target will always be Wivenhoe. There may be some questions, but they will only be minor, even though I feel sure they will be blown completely out of proportion.

Wivenhoe was never going to hold back that amount of water, and having no control over the downstream Bremer, the flooding in Brisbane was inevitable.

All Wivenhoe did do was to mitigate the effects of this major flood, something it was designed specifically to do.

It was not designed to prevent a major flood, just to lessen its effect, and this is exactly what it did do.

The scale of this disaster was huge, and had it not been for Wivenhoe, it would have been considerably worse, on a scale unimaginable.

UPDATE 3

The value of the water resource to the Queensland Government

What is something also worth considering in all this is the value of the resource of all that water held behind all the dams in the South East Corner to the nominal owners, the Queensland Government, who sell that water to consumers.

The new mindset is to protect that resource at all costs, by telling us how precious the water is, and how the Government is seen to be doing something for all of us, and you only need look at the TV ads about just that. There was the campaign to use less water around the house, and who can forget the Government mail out to every home of shower timers, and how we should limit our showers to three minutes, and perhaps even shower less. There was the need for all of us to change the taps around our homes and in the showers. The Government even introduced measures for consumers to call in government sponsored plumbers to evaluate our homes for water security.

This now became a case, not of providing for their constituents needs at every turn, but a case of protecting the source of that Government revenue.

This is classic ‘user pays’ and from the side of politics that used to beat their opposing party about the head with just that same stick.

As I mentioned in the second of those Background Posts, with the aid of those Wivenhoe capacity diagrams, during the major drought Wivenhoe went from 100% down to its low point of 15%. However, that took eight and a half years, and there were no restrictions, and water was always plentiful for every use, be that residential, commercial or industrial use.

The cost of that water at the time was also cheap, in fact, the cost was almost negligible.

However, as that low point of 15% approached, firstly the Beattie Government, and then the Bligh Government started to ramp up the prices and impose progressively more draconian restrictions upon the consumption of that water.

At the same time, the Government also introduced measures and legislation to ‘secure our future water’ with the construction of a ‘water grid’, all this at enormous expense.The Minister at the time whose initials are ‘lead me to the cameras’ said in that interview I quoted with CoastFM (ABCFM Gold Coast) that drought was the new norm we would all have to get used to, and that these large dams like this would never be full again, adding that we all needed to pull together on this, and that all this expense was imperative if we were to have enough water for that South East corner.

The cost to consumers for water usage was also ramped up, and here I’m not talking just minor inflationary upward pressures, but with the introduction of considerable increases for the cost of water.

There is a current forward plan for water costings which will be progressively staged in over the next (now) 6 years and at the end of that time water will cost consumers $2.75 per Kilolitre. (KL)

Extrapolating that out from what it costs now until then, those costs will average around $2.25 a KL.

The current holdings of all dams in the South East corner water grid amount to 2.3 million Megalitres. (ML), half of that alone stored behind a 100% full Wivenhoe.

That makes the current worth of that resource to the Queensland Government $5.2 Billion, in today’s dollars.

It only stands to reason that the best practice for the Government is to have those dams as close to 100% as is possible to protect that huge income for the Government.

Anything above that 100% is flood mitigation capacity, and must be discharged into the rivers as soon as is practicable after the rain event that fills those flood mitigation compartments of (some of) those dams. However, any discharges will only take that specific dam level back to the 100%, and here you seriously wonder if this is not a Government directive, not to discharge to a point lower than  that100%. With clever management of that water resource and the construction of a vast network of pipelines connecting major dams, then water can be moved from dam to dam to keep those major dams at, or close to 100%, which is the water supply total, and the water that is then sold to consumers, that Government resource, in effect, a ‘Tax on God’.

To reduce those major dam levels to a level where they can better mitigate large rain events that might cause flooding then becomes a case of flushing a valuable resource (for the Government) into the river and out into the ocean.
If (as shown by that chart in the previous post) the water in Wivenhoe took eight and a half years to get from 100% down to the low point of 15% with no restrictions whatsoever, then in the current mindset of the highest level of restrictions on water usage, that 100% now will take a lot longer to decay to that low level, even were we to enter another period of prolonged drought, and might even stretch out well beyond 10 years, if there is little, or even no rainfall whatsoever.

That’s not to say that lowering the level of Wivenhoe well down below 100% would have helped in this flood, because so much water went through the 5 gates at Wivenhoe, but the intent of the Government is plain to see here.

Keep those levels at or as close as possible to that 100%, because it is a source of large amounts of revenue for the Government.

Those water costs are the base price calculated at a rate of 140 litres per person per day.

Any water usage over and above that amount extrapolated out over the year becomes excess water usage and there is a (considerable) extra cost for excess water consumption, no matter who the consumer is, at the residential, commercial and industrial level.

Of that total water resource for the South East corner, half of it is contained behind the wall of Wivenhoe, so that monster dam contains water worth $2.6 Billion for the Government.
Now perhaps you can see why they maintain the level at 100%.

wivenhoe01

Advertisements