CURIOUS DROUGHT
AN OBSERVATION OF THE CONFLUENCE OF STATISTICAL ABERRATIONS, DAM RATIOS, TIMING AND UNCOMMON RAINFALL EVENTS THAT COMBINED TO HAVE OUR LEADERS DRAW INCORRECT CONCLUSIONS. THEIR INFLUENCE ON ACTIONS TAKEN.

Author : J. V. Hodgkinson F. C. A. Chartered Accountant : Aug 2006 to November 2013    

The principal thrust of this website is
FLOOD PROOFING BRISBANE from damaging floods to the point of extinction. MITIGATING flooding in Ipswich and Gympie. Putting REAL MEANING into "Drought proofing SEQ" and ensuring our water supplies by natural means well into the future

This is my review based on official statistics and documents. It is done in conjunction with Ron McMah, grazier of Imbil and Trevor Herse, retired of the Gold Coast

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Home

 

June 2009: Update and change from Home page


The following was the original initial page of the Website until April 2009. Website statistics tell me that well over 20,000 separate computer have accessed this site and most marked it on their "favorites" for later review. This section provides the base to examine the decision or no decision process of our Leaders and the consequences thereof in the new index page.
 

There have been some refinements over the two year period in both data precision and visual clarity. Of particular interest is my "Frequency of uncommon events" drawn from Bureau of Meteorology and an "updated Wivenhoe dam level graph to 2009" which may assist those reading this for the first time.
Low pressure systems 1841.jpg (116692 bytes)Wivenhoe Uncommon to 2009.jpg (86136 bytes)

 

 

 

 

Update on late February/early March rainfall and inflow (8th March 2010)

The Late February/Early March rainfall has seen our dams increase from 69% to 97% as Flooding Rain 08 03 2010.jpg (61098 bytes) at the 13th March 2010. A click on this photo will give one a comparison of the rainfall at flood time for all large events in the short life of the Wivenhoe since its commissioning in 1986.
Photo : Rainfall comparison

 

The Department of Environment and resource Management (DERM) have been good enough to provide me with the inflows that would have occurred if the dams and other Inflows1988 to 08032010.jpg (61098 bytes) infrastructure were not present. This provides us with sufficient information to judge the inflow from the recent February/March 2010 event which inundated Western Queensland. Our catchments benefitted from the same weather system. Comparison is made with all major events in the short life of the Wivenhoe.
Photo : Inflow comparisons

Wivenhoe Uncommon to 2009.jpg (86136 bytes)All of these events overflowed the dams with the exception of 1996. 

With no large events to fill our dams from 2001 to 2007, four near-misses rescued us from 2007 to 2009 the largest being May 2009 which failed to come west enough to cover the Wivenhoe catchment. Cyclone Hamish missed us altogether.
Photo : Wivenhoe dam level graph

These large scale events are random with an an average of 3.7 years from 1841. Most Frequency plus gap years.jpg (180089 bytes)occur below 3.7 years and as a consequence, a small number exceed this average by a wide margin. Their absence was misread as a drought. There was no provision for their extended absence although it was evident in the dam level graph, even to the unpractised eye, that eventually extreme difficulty would be experienced  in a protracted absence.

The evidence is now conclusive that Large Scale Events are our main water supply. We have all just witnessed a 30% fill from the recent event. While it was a major event out west it was a comparatively minor event in our catchments as evidenced by the rainfall comparison. The short history of the Wivenhoe shows us that 5 out of 6 overflowed the dam. Our dams are too small to accommodate these inflows and control our water supply for the benefit of our ecology and residents of South East Qld. We have the solution and it follows below.
Photo : Frequency of large scale rainfall events.

 

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August 2007:

 What this web-site is all about. 

It is acknowledged at the outset that various parts of Queensland and Australia are, or have been, suffering the ravages of drought conditions. In Queensland in January/February of 2008, actions of Monsoons have caused a great deal of the State to be flood declared. These events assist us in understanding the operations of our Dams systems.

This web-site deals specifically with the catchment areas of the Wivenhoe, Somerset and the proposed Traveston site. It identifies the true root cause of the recent low water levels within the Wivenhoe and Somerset Dams and proposes a potential long-term solution that is simple, low cost and effective.

SHORT SUMMARY

Primarily for those who require a quick overview. It will also give a sense of direction of the web-site. If I have been concise enough, reading of the first 20 paragraphs should be sufficient for the reader to gain an understanding and perhaps form a view.

"THE WORST DROUGHT IN 100 YEARS"

In late 2005 and into most of 2006 like all of the people of South East Queensland I was convinced that we were in the grip of "the worst drought in 100 years" with variations added such as " but only in the catchments", "its official, the lowest on record". The Television commercials and graphic pictures, principally of the Wivenhoe, drove the message home that a drought was in progress and it was like no other.

Is it a drought?

Although we felt the effects of a drought, things were not what they seemed to be.
A look at the Bureau of Meteorology rainfall for the six years to 2006 tells us that the water producing Summer months December to March have been quite normal compared to the long term averages. This is continuing into the 2007/08 period with Dam levels in the region of 38 percent in April 2008, a rise of around 20%.

Depleted Wivenhoe.jpg (264602 bytes)Wivenhoe_65_06_Sum_Non_Sum.jpg (267816 bytes)

 

 

It seems that the source of that term was a map from the Bureau of Meteorology (BOM) called a “decile map” which showed the rainfall received in our dams for Brochure.jpg (257138 bytes) the 6 years to Brochure matched with Percentage.jpg (122322 bytes) 2006 was at the lowest level of the historic averages. The actual rainfall for that period was close to 80 percent of long term average and that means that the rainfall has never been less than close to 80% since records were kept. To me this does not paint the true picture of our rainfall in the past six years nor does it help in making decisions about how we tackle the problem now.

I think the map misses a key fact. The water in our Dams comes from two sources.

The First is normal rainfall that we see every year – most of it coming from the high impact rain that falls in the four short Summer months with little inflow from the remaining months. We have viewed in the above chart that the deficiency of 20% in the six years to 2006 was all in the non-summer months which rarely create inflow.

The Second and most significant source of our water comes from unseasonal deluges –  typically associated with Monsoons, Cyclones or large Low pressure systems.  They do  Uncommon events 20th century.jpg (295642 bytes)Summer Rain Courier Mail 10 02 7.jpg (371046 bytes)not occur every year but, on average, every twelve years in tight groups of two or three years. When they do come they generally cover the whole of South East Queensland and have the capacity to fill and overflow our dams. They can occur at any time during the year.

BOM support twentieth century chart.jpg (196054 bytes)As an example, in a few days the dams can take in the water of 9 years of normal average rainfall. The Television pictures of the Fairburn Dam in Central Qld of January 2008 remind us of the Monsoon's powerful ability to fill large Dams in a few days. SEQWater is to the point and calls them “uncommon events”.

The chart above has been compiled from Bureau of Metrology rainfall data. It reflects the rainfall required by SEQWater to produce an uncommon event. The Bureau's flood information chart, on the right, has permitted me to form an opinion that the rainfall requirements are accurate and the past uncommon events are clear. Notice that flooding below the dams since 1986 represents water not able to be held by the dams.

The reality to me is that, as our population increased, we have come to rely more and more on the store of water from these large deluges ( uncommon events ) – the regular Drop in Dams Megalitres to rain.jpg (205378 bytes) summer rains have long since been insufficient to meet the needs of the region. They provide 11% annually to our dam capacities and the population requirements are 22% under business as usual conditions. The draw down from full dams in times where these deluges are absent is therefore 11% which is 9 years supply. In the 6 years to 2006 we have seen that happen. The dams were full in 2001 and were around 18% capacity in late 2007 rising to around 38 percent in April 2008 with above average Summer rain for 2007/08.

Dam levels and uncommon events in the life of the Wivenhoe : In the short life of the Wivenhoe commencing in 1986, the Wivenhoe/Somerset system  received 5 out of the 17 Dam levels official revised Wivenhoe.jpg (151526 bytes) uncommon events of the Twentieth Century. They occurred between 1988 and 2001. This graph supplied by SEQWater shows the constant fill to overflow and draw-down of our requirements until the next uncommon event. The uncommon events finally ceased in 2001 with the draw-down in requirements continuing.

The previous uncommon event was the 1974 flood. Under current conditions, the surplus water would have lasted 9 years to 1983 leaving a gap of 5 years to 1988.
The Twentieth Century type gaps that normal summer rains have to bridge are listed in the the previous charts. They are :-

 14 years. 1974 to 1988 
 10 years. 1956 to 1967
 27 years. 1928 to 1955 with one in 1950 intervening
 19 years. 1908 to 1927
 10 years. 1898 to 1908

The Bureau of Meteorology Flood information chart above shows that large gaps were not evident in the last 60 years of the 19th Century. Natural climate change was evident in the first half of the 20th Century. A return of an 1841 or 1893 flood compared with the 1974 flood would make for very interesting calculations.

What does this mean?

The good news is that the grid system excluding the Traveston Dam will go close to providing sufficient water to make up for the absence of uncommon events. The bad news is that it will not provide relief for a genuine drought and does not provide for any increase in population nor does it provide for a refill of the dams. 

The whole system awaits an uncommon event to take the pressure right off and provide insurance against a real drought. There is no requirement to draw against it at least for some time as the Grid and Summer rains take care of our unrestricted needs. 

The longest gap between uncommon events in the twentieth century was 22 years with the last gap from 1974 to 1988 being 14 years. We are 7 years into a gap, from 2001 to 2008. The filling of the Hinze Dam in January/February of 2008 has provided some relief. In addition, the current above average fill in the Wivenhoe/Somerset of around 20% to 38% of capacity from above average summer rains will provide more than sufficient time to bring the grid system on-line in year 2008.

What the Queensland Water Commission believes the situation to be.

In their "Water report" published in the Sunday Mail on the 20th April 2008, the second paragraph leads off with "Smart water use is now a way of life - even when this drought breaks".

To me, the known facts are that we have survived totally on Summer Rainfall December to March since February 2001. The Dams were full at that date and have been reduced to the current April 2008 level of 38%, a period a little over 7 years. You will see that the Summer rainfall overall has been quite average. The first 3 to 4 years were with unrestricted use with no apparent concern by those in charge of the developing situation.

It follows that the "Uncommon events" are included in the Water Commission's definition of a "drought".

It is clear from the above information on "Uncommon events" that their provision to our water supply, while very large, is completely unreliable in timing. The last gap, 1974 to 1988 was for 14 years. On that basis, it is my view that the Water Commission type "drought" may not break until year 2015.

The answer lies in the management of the water from "Uncommon events".

Understanding the Dams and their catchments

It is useful at this point to gain an understanding of the operations of the Wivenhoe and Somerset Dams and their catchments. In my view, a comparison with the Traveston proposal can then be measured.

The Somerset and Wivenhoe Dams are placed at the junction of two Rivers. The Stanley River, which is closest to the coast, and the Upper Brisbane River. The Stanley River feeds Catchment_map_with_contours.jpg (249481 bytes) into the Somerset Dam as a temporary measure which then releases all its water into the main storage Dam, the Wivenhoe. The Upper Brisbane River feeds directly into the Wivenhoe at that junction and the Wivenhoe releases, when required, into the lower reaches of the Brisbane River.

Comp Som Wiven Sum 65 06.jpg (230709 bytes)The catchment of the Stanley River is 1/3 the size of the spread out catchment of the Brisbane River but three times more efficient. The Stanley River receives 30.8% more rainfall which converts to a much higher inflow figure ranging beyond 50% additional water. Most of this water is stored in the Wivenhoe which also has a flood mitigation compartment larger than the normal water supply.

The Bureau of Meteorology has confirmed that in three year periods, the catchments have never received less than close to 80% of the long term average.

The Stanley River catchment, which feeds into the Somerset Dam, is by far our largest water supply source. In the most recent rainfall from the 4th January 2008 to the 12th February 2008, the Stanley River provided a flow of 147,595ML into the Somerset Dam. The Upper Brisbane River provided a flow of 78,199ML into the Wivenhoe Dam (SEQWater website). There were minimal releases to that point. That amounts to 65% of our water supply coming from the Stanley River which is about equal to my calculations in this website.

Traveston Dam proposal

Our Leaders look to the future with the Traveston Dam. The Traveston dam catchment rainfall has almost exactly the same pattern and timing  as the rainfall in the Wivenhoe and Mary Val and Somerset Summer.jpg (234529 bytes)MV Summ compare flood 65 to 06.jpg (205041 bytes) Somerset Dams. It is not surprising as they are adjacent. Its Supporters say that it stands up to Hydrological modelling. The most recent and rare August 2007 low pressure system over the Sunshine Coast is quite a minor player in size and location.

 It is my view that the Traveston Dam will eventually be in the same position and at the same time as the Wivenhoe and Somerset in attempting to bridge the gaps between uncommon events.

The solution.

Wivenhoe/Somerset system

In 1974 and in the recent period of 1988 to 2001, a great deal of water from the catchments found its way into Moreton Bay. In addition the Wivenhoe Dam was filled from scratch in 1986. Our historic experience is that unless we can harness the surplus water from these deluges, we are not likely to see a long term solution to our water supply problem. 

Government appointed Engineers quantify this water as 80,000ML annualised over a 110 year period. Of course it occurs in large bursts.

The people of the Mary Valley have pointed out that the Borumba Dam expanded to 2 million ML is an ideal  Top of ridge look at dam TH.JPG (353942 bytes)Map Borumba.jpg (312591 bytes)storage dam. The provision of a suitable dam wall would increase its capacity to twice the size of the Wivenhoe dam.  It has been reviewed on the basis of a normal dam and discarded. My review of the reports used did not disclose any evidence that it has been seriously considered as a storage dam for the surplus waters that would normally go over the spillways of the Wivenhoe/Somerset system and the Borumba Dam during these uncommon events. This most likely occurred because, in my view, the Consultants were not provided with a suitable "Terms of Reference". My views on the reports used are expressed in pages 4 to 8 of the Environmental impact study (EIS) in this website.

This surplus water is now out of our control through lack of storage capacity. The draw down from Borumba would occur when these large gaps between uncommon events are encountered. As we are replacing the water taken from the Wivenhoe, the Wivenhoe/Somerset system dynamics are unchanged and, as you will see elsewhere in this website, vastly improved for this stressed system.

Borumba Dam

As explained, the Engineers advise that this small dam can be expanded to 2 million ML and beyond if required. This is almost twice the size of the Wivenhoe/Somerset system. The Borumba Dam is just over the hill from the Wivenhoe Somerset system (60klm). With the  very Moreton resources.jpg (141612 bytes)Gympie Times P2.jpg (361826 bytes) large excess flood holding capacities of the Wivenhoe Somerset system, the pumping time required would be adequate. The flood holding capacities of the two dams is 1,974,000ML, almost twice the size of the Wivenhoe Dam.

In times of deluge the Borumba Dam is no slouch with a rock hard catchment. In 1999 a volume of water equivalent to one half of Sydney Harbour went over the dam wall in a single day. The event lasted 5 days.

 

The official statistics confirm that 91,000ML flowed over the Borumba Dam wall for its entire life since 1964 on an annualised basis. It does not happen annually as it is the product of "uncommon events".

Storage space for uncommon events

With the introduction of the Grid System to replace uncommon events, there will be little requirement to draw on the dams. After the dams are replenished by the first one, the rest will largely go over the spillway with possible major flooding.

The Traveston proposal locks up permanently the Borumba Dam to 40,000ML annually ( it is part of the 150,000ML of the proposed dam) and the Dam footings will block the creation of the 2 million ML plus Borumba storage dam.

Calculations reveal in this website that 125,000ML, on an annualised basis, can be stored in the expanded Borumba if the Traveston proposal does not proceed.

THE SOLUTION SUMMARY

The mathematics are :-

My proposal

Wivenhoe/Somerset control of uncommon events - 80,000ML

Borumba Dam expanded to 2,000,000ML surplus from uncommon events 90,000ML.

Ability to store uncommon events surplus to our needs 125,000ML

TOTAL 295,000ML

Traveston crossing dam proposal

Borumba Dam with minor expansion 40,000ML

The Mary Valley Catchment 110,000ML

TOTAL 150,000ML

The proposal can be viewed from page 8 onwards in Final Solution & EIS. The previous pages in that section relate to my views on the material presented to the public.

Allied matters

All the land is owned by the State Government on behalf of the people of Queensland.  PowerLink TH.JPG (524710 bytes)There is no interruption to our neighbours’ current way of life on our behalf. I expect the cost to be considerably less than the 2.7 billion dollars currently estimated for the Traveston dam construction and infrastructure changes.

 

Root cause

We have seen that the root cause is the lack of understanding of these deluges known as “uncommon events”. It is my view, with the benefit of 20/20 hindsight, that our past leaders were unaware of their implications and cancelled the Wolfdene Dam. We are now paying full price in lack of water and second class costly options.

Our current leaders' public pronouncements clearly blame the “drought”. If they insist that it is a "drought" then it is the type of drought that can take up to 21 years to break based on the chart of the last 109 years shown above. I hold the view that they are unknowingly following the same path as our past leaders. The window for the Borumba Dam proposal is closing and will soon be lost forever as was the Wolfdene Dam.

Climate change

There are two types of Climate Change. 

The first is Natural Climate Change that we experienced in the first 70 years of the Twentieth Century.

The second is caused by the World's exploding population and its energy requirements

To handle both types of Climate Change, a significant buffer is required. The Borumba Dam expanded to 2 million Megalitres is that buffer. Its expanded capacity will exceed the total capacities all all Dams in South East Queensland. You will see that it can be filled from our current water available without the Traveston Dam. It has the capacity to expand further but that would require considerable courage on the part of our current leaders.

For those requiring serious examination, it is contained in my submission to the Traveston
Crossing Dam proposal under alternative methods. The Link is Final Solution & EIS. The
back button will return you to this page.