What is fresh water? Don't be too quick to say it's a precious natural resource. To me fresh water is energy. There is heaps of water on earth it may just not be where or in the form that you want it at the time that you want it. You will get fresh water anywhere you want it in any quantity if you are willing to provide the energy and infrastructure to get it there. To me energy and infrastructure are fairly similar too as infrastructure is produced at its source by energy.
When we look at conventional forms of water supply consisting of dams and piping systems we don't see the huge energy costs involved or the massive environmental damage caused by these schemes. The biomass destroyed in the flooding on the valleys upstream of the dams alone adds millions of tonnes of green house gases to the atmosphere.
Building the associated dams and infrastructure utilise massive resources in the construction and manufacture of the component parts. Once operational we then forget about the massive pumping that has to be undertaken to get the water to the point of supply at the pressure we want to use it at. In many cases the electrical usage of present systems rival that of desalination systems. For example Sydney Water has always been one of the biggest users of electricity in the state of NSW.
As such I see desalination plants as an undervalued solution to at the least the drinking water needs of this country. As the efficiency of these plants increases with technological developments and as the supply of green energy increases I see desalination plants being a long term solution to the water supply issues of this country. I also look forward to a time when green energy and desalination plants can result in the decommissioning of many of the dams (both hydro and water supply) built in sensitive environmental areas such as Lake Pedder, the Snowy mountains and Warragamba. Returning these areas to nature will also recreate these places as the large carbon sinks that they once were.
Unfortunately one of the draw back is that a lack of water has always been regarded as the reason this country can't sustain many more people than we have currently. Desalination plants take away this natural constraint. I see a great deal of environmental damage done to this country (and the world in terms of Australia's growing Carbon footprint) as a result of Australia's ever increasing population. It is hoped that we can take stock as a nation and stabilize our population despite the fact that the water supply issue is no longer the population constraint that it once was.
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Comments
what about water recycling?
An interesting series of points regarding desalination plants, and I'm wondering if the same is true of water recycling technologies.
Although the idea of drinking and bathing in recycled water irks many Australians I wonder whether it isn't a more appropriate solution to the water shortage, and I suspect it irks them because they aren't all that familiar with where the water they are currently drinking comes from anyhow.
How do recycling technologies compare to desalination technologies? Are they similarly costly, and are you suggesting desalination ahead of recycling, if so, what are the pros and cons of each.
JV
Recycling
Sewage is normally treated to various degrees before being released back into the environment or out to sea. The standard forms of treatment use significantly less energy than desalination and enable the water to be used for industrial purposes. To make it safe for drinking water, similar technologies and infrastructure to desalination have to be used. As the sewage has to be treated anyway it can be considered that the cost and energy use of producing drinking water from sewage is significantly less.
I believe that water recycling from sewage particularly for industrial use should be used in preference to desalination. However, recycling of sewage can not meet the demands for water so substantial other means of supply are needed.
Recycling of stormwater has been mooted. This is considered and used currently only on a local scale at low levels of treatment and capture for use on ovals etc. I'm not aware of any water authority that takes it seriously for use on a large scale. It's only the media and politicians that choose to spruik what I consider to be a Furphy of an idea. In general drinking water is captured close to its source over brief durations (e.g. rain events) in a close to drinkable state and stored nearby (e.g. dams). It is then distributed over the entire year via suitably sized piping and pumping systems.
Urban stormwater occurs by nature in built up urban areas and is produced in quantity only during rain events. Urban stormwater by nature isn't clean and needs to be stored firstly for purification and secondly for distribution. There is no room to store this stormwater in quantity at its source in urban areas. It would therefore have to be pumped to a special dam prior to purification. As it is produced in short duration rain events (usually minutes to hours long) the pumping systems and pipework need to be relatively huge to handle these quantities over short durations. Remember that existing systems distribute water over the entire year whereas rain occurs for only a number of days a year. This tells you the size of infrastructure that s needed. (much larger than existing distribution systems). Due to the volumes involved the stormwater cannot be treated as quickly as it is sourced without equivalently huge treatment plants. Therefore large dams or reservoirs would need to be built just to store the dirty stormwater prior to gradual purification over many days. Again due to the urban build up the stormwater storage would be on the outskirts or in the hills. Therefore these very large pipe systems would need to travel for large distances through or under built up areas. Once stored and treated the treated stormwater can then be pumped and piped to existing storage systems for distribution by current means.
I hope this demonstrates why stormwater recycling is such a Furphy of an idea.