“So either were talking about lots of little purification stations, or we’re talking about building infrastructure to move stormwater to a few places. Somehow, it starts to sound expensive.”

Well, no actually- they can be very cost efficient. The Rocky Mountains Insitute in the USA is frquently used by all levels of Government and private business on a huge range of projects with an environmental aspect. The material on this page gives cause for optimism http://www.rmi.org/sitepages/pid172.php#W04-21

Anyone with an interest in cost effective solutions to environmental issues should read the RMI book “Natural Capitalism”. It gives hundreds of practical examples of water, energy, materials etc saving schemes that have cost very little or, more often than not, saved money.

It is always raining at Ourimbah, it never rains at Bucketty yet the dam went in. If they had better management then….

The cost of the energy is included in the stated cost of the desalinated water. However, it is not the major component of the cost. A large scale desalinator runs on about 3kWh per kilolitre, which is around 30cents worth of electricity.The major cost of desalinated water is the cost of capital used to build the plant, and the plant’s depreciation.

There is an external cost in the form of CO2 production and other polution as a result of the energy consumed. As yet there is no agreed way to quantify that cost.

Sydney’s desalinator project was killed off (or at least put on the back burner) more by politics than economics, and by the discovery of some bore water that will at least postpone the decision to go ahead with a desalinator until after the next election.

Sylvia.

How do you work the costs of the energy concerns of desalinaton into your eqautions. That was one reason for the killing of the Sydney project.

However, most houses are not on new estates, and the cost of retrofitting a second distribution network to the existing housing stock would be prohibitive. It would also be extremely disruptive. You’re talking about digging up every residential street and front garden.

It’s also difficult to imagine that enough of the retrofitting could be achieved in time, given that dire state that the politicians have allowed the reservoirs to reached before admitting that there’s a problem that can’t be solved by just getting people to use less water.

I haven’t looked in any detail at the idea of using storm water runoff, but a one issue comes immediately to mind, which is that it comes in bursts, so would need to be stored somewhere. It would have to be purified to potable water standards before it could be distributed through the existing network. Also stormwater is just dumped out to sea at a convenient point. It is not currently collected at a few central points. So either were talking about lots of little purification stations, or we’re talking about building infrastructure to move stormwater to a few places. Somehow, it starts to sound expensive.

Don’t get the idea that I have some philosophical opposition to anything other than large scale water operations. I don’t. However, the community is best served by getting solutions that have the lowest cost commensurate with the requirements. Finding those solutions involves rather more than pulling ideas out of the air and assuming that they are cost-effective.

Mark, the $4 per kilolitre figure is for the proposed mobile desalinators, which are presumably all that can be achieved in time. A fixed desalinator would provide water at a lower cost, but has a significant lead time.

One of the big problems with non-potable water, as I understand it, is that all our infrastructure is set up to distribute one grade of water, and that’s the drinkable stuff. Duplicating infrastructure to distribute non-drinkable water is expensive.

By the way, where does the $4/kilolitre figure for desalination come from? Quiggin, in his posts on the matter, tends to quote around $2/kilolitre.

The ABS says:

“Household water consumption increased by 13% since 1996-97 to 2,181 GL in 2000-01. On average each Australian consumed a total of 115 kilolitres (kL). While Australian households consumed an average of 280 kL. The majority of household water was used for outdoor purposes (44%), such as water for gardens and swimming pools.” see http://www.abs.gov.au/ausstats/abs@.nsf/e5cb0b45f4547cc4ca25697500217f47/cc9d340e1feef80bca256e9900810f09!OpenDocument

Sylvia, does it really make sense to desalinate sea water at great expense in order to water the garden and fill up the swimming pool? Moreover, much of this drinkable water will be used by industry in processes that do not require highly purified water. I’m sorry but this makes no sense at all.

It has cost me less than $300 to cut my water usage in half we a rainwater diverter from the roof to the garden, super efficient shower nozzles, shower timer and so on.

Also Sylvia, why not

-capture and purify urban storm water run off

- treat sewage water for agricultural use (as per Melbourne)

- require new housing estates to capture and recycle rain water

- etc etc etc

All of these types of options should be compared in terms of cost (including environmental externalities) with the proposed $4/kilolitre desalination plant.

Details here:

http://www.ourbrisbane.com/living/realestate/propinvest/archive/bucketsofmoney.htm