Please click on here to download Analysis Supply and Demand Melbourne’s Water - Version 4

An explanation of the Y.W.Y.S. Supply/Demand charts (V4, April 10th, 2008) and the consequences of adopting different water augmentation options.

This version still incorporates the new population projections for Melbourne (suggesting an additional 1 million population for Melbourne by 2020). It also has available dam inflows reduced by the CSIRO’s most severe long term figure on top of the last ten years of drought (there will be excesses greater than these shown, if the current drought cycle eases).

Firstly I would encourage anyone interested in understanding the options that Greater Melbourne has for securing its water needs into the future, to look at the policy the State Government presented to us at last election. The document is called ”Sustainable Water Strategy, Central Region, Action to 2055”. You can still ring DSE on 136186 and request that they send you a copy (it’s free but you must ask for it by name).
The government did two years of good research, working with Melbourne Water and the CSIRO, to arrive at a sustainable strategy to secure water needs through until 2055. Unfortunately after the election the government decided to squeeze in a huge desalination factory as one of the first options, rather than a last resort. Desalination had always been mentioned as a possibility but had been described by the government as being expensive, intrusive and energy intensive, before the election.

A time scale for the different water sourcing options and likely capacities for each was given in the “Actions to 2055” document. These have been used, a few conservative estimates for others not specified (referencing other government documents) and the new time/quantity figures for the government’s new options (the desalination factory and the Sugarloaf Interconnector). We need to have supply of water above demand, at least when averaged over time. The charts present a convenient way to see, year by year, how much excess water will be sourced each year, from the augmentations implemented to that time.

The most significant fact that can be derived from analysing these charts is, that we do not require an unnatural rainfall independent source of water. Sustainable options to augment Melbourne’s supply will allow a more than sufficient quantity of water to be stored in our dams as an insurance policy against drought and climate change. We now have a choice to make, do we choose the sustainable or the unsustainable options?

The Charts:
Pages 1-3 give some background. The government’s highlighting of the 2006 low dam inflow figure and the use of a repeat of that three year scenario with no augmentation to justify a panic mode adoption of their current policy. A suggestion that Perth’s adoption of desalination might have triggered the Victorian decision is looked at showing we are not in the same situation. The inclusion of 2007 inflow and consumption figures show how different the situation can look with just one years extra figures. Throughout the charts 2007 consumption figures, adjusted for severe further climate change inflow reductions and population increase, are used as a base to work from. This figure is conveniently close to the government’s stated policy of getting consumption down 25% on 1990’s level, and so is a good figure to be using.
Page 4 Shows the order of supply augmentations now being proposed for greater Melbourne, with an annual level of supply reaching ludicrously large excesses above the 2007 consumption. The blue bar on the left represents the average inflow available for urban consumption over the last 10 years to our dams (while in drought). Each successive bar shows more supply added, year by year, as more augmentations are implemented. Have a look at the situation after the desalination factory comes on line in 2011, supply is around 66% greater than 4 years earlier. This excess would increase to 117% above the 2007 consumption by 2016 using the governments figures when given and conservative figures otherwise. Take note that the desalination factory on its own is a quantity around 40% of 2007 consumption added to supply ever year.
Page 6 takes into account the fact that with population increase and possible further climate change the difference between supply and demand will narrow. However even using the CSIRO’s “severe” scenario for further climate change inflows to our dams and government estimates for population increase (see references on page 7) the excess is still around 52% annually after the desalination factory is completed and possibly 83% by 2016. It begs the question, why so much water, and will the more sustainable options be swept aside?
Page 8 here the excesses of supply above demand (the black arrows) are considered as water that can be left in, or sent to, our dams. The dams have a capacity to hold over four years of supply at 1773GL total capacity. Annual storage levels are shown each year as the excess supply is left in, or added to the dams. Assuming the various augmentations come on line in the year after their completion dates, then in 2015 Melbourne’s total storage capacity will be full and overflowing on these figures! One would assume that the government would be unlikely to implement many further augmentations when Melbourne water users are paying for the desalinated water to run over the dam walls. Hence the more sustainable options look like never happening.
Page 9 is against government and Melbourne Water policy of sustainable usage, but shows even with 20% greater usage the quantity of water being sourced is still very much in excess after 2011.
Page 10 looks at a situation closer to the policy put to us at the last election. The desalination factory is removed, other option are left at the same years for introduction. Here the excess is still large indicating clearly that Melbourne’s water supply is secure. Remember these figures are effectively for worst case scenario of climate change reduction in rainfall and runoff to our reservoirs on top of the last ten years of drought. If the yearly excesses are added as in the chart on page 8 the dams will be shown to be overflowing in 2017, even without desalination. Not a bad insurance policy, and one achieved without the need for the vast amounts of energy needed to manufacture water by desalination, with all its adverse consequences.
Page 12 again not sustainable usage policy, but this chart shows that even with 20% more usage each year we could still be building an insurance policy in our dams by 2012, without desalination.

Note that although the figures used are largely sourced from government documents (see reference pages) some quantities may not be realisable and some of Melbourne’s supply may be sent to other areas. However the quantities will be a fraction of the excesses available in, for example, a no desalination option on page 10. Further, page 16 suggests some further augmentation options that could provide excesses even above the levels with desalination.

‘Your Water Your Say’ believes that this research clearly shows that there is no need for a desalination factory producing the most economically and environmentally expensive water.
We understand that climate change and population growth are having an impact on our ability to meet our water needs. The crux of the problem is that since the completion of the Thomson dam in 1984 successive governments have failed to invest dividends from Melbourne Water to implement augmentations to Melbourne’s supply. To this government’s credit, they have undertaken studies (‘Actions to 2055’ document) and begun implementing augmentations to meet future water needs. However an illogical step is planned with the proposed desalination factory. It will result in us swimming in water, but drowning in water bills and baking in greenhouse induced warming.

Please click on here to download Analysis Supply and Demand Melbourne’s Water - Version 4