Tips for Sydneysiders.

Current Dam levels
SourceSCA
Date2012-04-26
% full 96.85
1-week
% change
-0.50
Dams empty date (from 1-year differential)never
Sydney Dam Levels

Sydney Desalination Plant

Desalination plant options for Sydney - description and analysis. What would Sydney's dam levels be now if a desalination plant was already in operation? How much would a desalination plant cost? Are rainwater tanks and other water saving techniques more effective? Your questions answered. Statistics updated whenever Sydney Catchment Authority releases data. Last update: 2012-04-26 . Useful thoughts for people considering rainwater tanks or irrigation systems or saving water.

Sydney is experiencing something of a water crisis, so a Sydney desalination plant is under consideration. At the overall rate of water gain in the past year in the dams, they will fill in 813 days, less than 3 years and will overflow on 2014-7-18 . A desalination plant would have made a big difference to this. See also our extensive page on Warragamba Dam levels, Sydney Dam levels and statistics and also our page on Warragamba catchment weather. More links at the bottom of this page.

What are the options being considered for a desalination plant in Sydney?

The State government has (so far) mentioned two options for the size of a potential Sydney desalination plant. A 100 ML/day plant and a 500 ML/day plant. Sydney's usage is about 1500 ML/day. The desalination plant (or plants) would be placed in the eastern suburbs of Sydney and provide water to the eastern suburbs primarily through existing pipes. The energy minister, Frank Sartor, said that the plant would look much like a Bunnings Warehouse. The drawbacks of a desalination plant are its high start-up cost and high electricity running cost.

How much water would be in our dams now if we already had a desalination plant in Sydney?
The following table assumes that Sydney's usage and evaporation are the same with a Sydney desalination plant as without one. We consider the following Scenarios: The "As is" conditions (i.e. what has actually happened), the result of a 100 ML/day desalination plant running continuously, the result of a 500 ML/day desalination plant running continuously and the option of a 500 ML/day desalination plant which is only switched on whenever Sydney's dam levels are below 50%.
Hypothetical since 11.2001Available water (GL)% full all dams1year change GL(%)
As is 2500.5 96.85 583.00 (22.58)
100 ML/day 2551.25 98.81 289.65 (11.22)
500 ML/day 2552.85 98.88 -28.00 (-1.08)
500 ML/day when levels < 50% 2826 109.46 583.00 (22.58)

What does this show us? We can see that a 100 ML/day plant does not solve our water problems by itself. Such a plant would need to be run continuously and we would still be under water restrictions with such a plant. A 500 ML/day plant which is only switched on when dams fall to 50% of capacity would save electricity (given the history of our dam levels) and allow for a much more severe drought because it can provide a lot of water when we need it and be moth-balled almost all of the time. Of course, if the current drought is a sign of climate change rather than a temporary lack of rain then only a 500 ML/day plant will allow us time to take action. It is also interesting to note that dam levels would still have dropped under a 500 ML/day desalination plant in Sydney, so if climate change is occurring then this may not be enough!

Can't we just cut down our usage a little more instead of going for desalination?
We could cut down our usage some more, but if we run out of water anyway then this does not help! In the following table and graph we analyse some different usage scenarios (assuming no desalination plant). They compare current usage (under the water restrictions that have been in place) with what the water levels would have been if our usage had been (for example 20% less) than what it has actually been. Note that level 3 water restrictions reduce usage by about 3%-10% over level 2 water restrictions, so a 20% drop in usage is very significant! If everyone had rainwater tanks for their gardens, usage could drop by around 20% on level 1 water restrictions.
Hypothetical usage since 11.2001Available water% full all dams1 year change GL(%)
20% More 1430.655.41 501.24 (19.41)
As is 2500.5 96.85 583.00 (22.58)
20% Less 2551.898.84 -20.38 (-0.79)
50% Less 2553.298.89 -28.03 (-1.09)

From this data we can see that, provided the current drought does end in the next couple of years, using less water can be sufficient. However, given that a further 50% drop in usage would be required to prevent the dams falling in the last year, a Herculean effort would be required for Sydney to survive on its current rainfall and usage patterns if this drought is merely climate change and representative of a more permanent change in rainfall. Hence something more than this, such as a desalination plant, may be required.

What about the Shoalhaven scheme, and deep pumping from our dams?
Whilst deep pumping does help once each drought, it is not a continuous supply of new water. Only dams which often overflow, even during this drought, such as Tallowa Dam, could make use of such water more than once each drought. The Shoalhaven scheme is more promising, however. A desalination plant does have the most continuous source of water.

You can see the history of the Tallowa Dam water levels. In this you can see that Tallowa Dam often overflows. The Shoalhaven Scheme upgrade that is planned for the next few years is designed to transfer more water from Tallowa into the main Sydney system. The two stages of this upgrade are estimated to provide 80,110 GL/year. The effect of this (with and without a 500 ML/day desalination plant) is shown here: A 500 ML/day desalination in addition to the Shoalhaven Scheme upgrade does appear to be sufficient to keep dam levels close to steady in the current drought.

What about options to save water other than desalination
Several other options are under consideration. Water recycling is feasible for new developments, but would be expensive to introduce new pipes to existing suburbs. This would also take a long time to introduce (which we may not have if the current drought continues as fiercely as it is). Grey water, rain water tanks, water efficient appliances will all help, but not by the 50% figure we would need if this drought does not end. Of course if Sydney was happy to accept the mixing in of recycled water into its drinking supply then the introduction of large scale recycling could be done as quickly as a desalination plant. Unfortunately at this relatively late stage, time remaining is important... and a desalination plant, as environmentally unfriendly as it may be, is a relatively quick option.
Would the western suburbs of Sydney still be relying on dam water while the east gets a nice guaranteed supply of perfect desalinated water?
Yes and No! The current plan by the government does have the eastern suburbs getting the desalinated water, while the western suburbs uses dam water. However, it is not the case that the eastern suburbs will no longer need to obey the same restrictions as the rest of us. Each litre of water that the easter suburbs saves in water from the desalination plant means that the desalinated water gets to travel a little further west, reducing the pressure of our dams. If our dams were to run dry, extremely harsh water restrictions could be used to spread the desalinated water over Sydney.

Water quality is a different issue... the desalinated water should be of generally higher quality than water from our dams. This is particularly the case as our dam levels drop (decreasing slightly the quality of our water). The hardness of the two sources of water will also be different. The area of Sydney that is likely to receive the most difficulties with water quality is not the areas that rely solely on dam water, but the area that is in between that (during low water usage periods) sometimes uses desalinated water and (during high usage periods) reverts to dam water. For this area of Sydney the hardness of the water (and hence ph, as well as other factors) may change dramatically from day to day. This can make it difficult, for example, when keeping fish it is desirable to keep conditions fairly stable. A drop in water hardness can mean greater ph fluctuations and the possibility of a carbon crash. Perhaps this changeover area between water from the dams and desalination plant can be in the cbd where there are less plants to suffer, and aquariums are often managed professionally.

Sydney dam levels main page
This month dam level statisticsRainfall this week
Trends of Sydney dam levelsUsage and Inflow trends
Firefox Extension (SydDams)Interactive Catchment Map
Dam levels for individual damsSydney Desalination plant impact on dam levels
Reduced Usage impact on dam levelsHow to save water in Sydney
General Information on Warragamba and Sydney's other Dams
Home irrigation/watering systems in Sydney
Old location of Sydney dam levels page
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Comments by visitors:
by Peter Davies @ 10 Jul 2005 10:51 pm
I am organising a scenario planning workshop on urban water management in early August involving a range of state and local government senion managers, water researchers, industry and others. I would be interested to discuss yor web information and the planning session with you.
Regards, Peter
02 94240745




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