Water tanks are not a mainstream solution for cities. Simply; the water catchment area must be considerably greater than the urban area. It must also contain a variety of sources and large storages. Any home based system can’t properly drive the sewer. A fully recycled home based system could become deadly. Appropriate treatment requires delicate engineering and science. To do that sustainably we may resort to buckets. It’s much easier to live on bottled spring water from the supermarket.

Lyn wrote around the concept of limits. Consumer demand is insatiable. For several decades I worked in Melbourne’s rapidly expanding industries and the vast MMBW systems that sustained the urban population. When recycling the Lower Yarra seemed the only option we prepared in haste for a lower grade of water that depended heavily on an overdose of chlorine at the tap. However, not all suburbs would need to suffer. The Thompson River project finally saved the day for everybody.

Technology has not changed much since the 1960’s and 70’s. Fluoridation is now well established everywhere. Reverse osmosis filtration and deionisation plants help our major industries such as food processors to reach new standards. Bottling and packaging replaces buckets and baskets. High-rise dwellers don’t have a compost heap either, but their flushing goes on and on. 100lt/person/day is a luxury, any more is just pure waste.

The reality is that one million homes in Sydney are able to yield 80GL of water a year costing $1.25/KL; one million homes in Melbourne can yield 70GL costing $1.45/KL; and 700,000 homes in southeast Queensland can yield 50GL costing $1.45/KL.

Mean annual rainfall of 85% means up to a 50% decline in water inflows into dams serving coastal cities. Desalination plants, obviously, will struggle to replace losses due to climate change and reduced rainfall. Population increase of 25% over the next 25 years will increase water demand by 25%. Consequently, rainwater tanks are a cost effective and technically achievable addition to the nation’s urban water supply.

It is true that in Sydney, four 670 litre rainwater tanks will allow 80KL of water each year to overflow into the stormwater system. However, nearly 80KL will be used by the householder costing $1.25/KL.

It is a different story in Melbourne. Four 670 litre rainwater tanks will provide 70KL of water a year costing $1.45 a kilolitre and the overflow will be about 12KL a year. Melbourne has about 50% of Sydney’s rainfall but it is evenly dispersed throughout the year, whereas up to 50% of Sydney’s annual rainfall occurs in a handful of rain events, typically round 100mm in a day. Mains water in Melbourne will cost over $1.60/KL when the price doubles within five years.

Brisbane has a lower annual rainfall than Sydney but a similar rain pattern. An average Brisbane household will yield about 70KL of rainwater a year from four 670 litre rainwater tanks costing $1.45 a kilolitre. Overflow will be about 70KL a year.

Naturally homeowners can increase their rainwater yield by installing larger tanks.

The 670 litre tanks used in my estimate are low cost because they are made by plastic injection moulding and are designed to achieve economies of scale in delivery and installation. Larger tanks are more expensive to deliver and install, and once filled, overflow at the same rate as four 670 litre tanks. In general, large tanks installed for existing houses provide more expensive water.

Greg Cameron

Greg: The reality is no academic can solve our problems with a bundle of stats or for that matter a pile of plastic tanks. Working with water and sludge was my biz. Finding good trades for doing all the fiddly bits was my speciality. Let’s say the hard yards from here on besides monitoring industry is metering the activities of folks hiding in high rise.

After experiencing some of the wettest conditions in this country I now live in the MDB region most affected by continuing drought. 50% of our town water once went on suburban gardens. These days we let even the street trees die. Climate change in this district close to the Great Divide is severe. Rainfall anywhere is quite uncertain, plumbing any sized tanks to my five downpipes is almost a total waste of time and the Murrumbidgee would suffer. After all, who owns that occasional drop falling on my head?

Water authorities here are currently investigating expanding our sources to include those existing dams in the Snowy Mountains hydro scheme. Desalination for this region could cost billions after a review of the engineering involved in getting seawater over the divide. High tech treatment of sewage is a much cheaper option but even that involves extra dam capacity. There is no convenient marshland for a natural UV treatment stage.

Professional advice is available on our situation in some 30 recent reports. See other links on salt management and health.

http://www.actew.com.au/waterSecurity/default.aspx

Seawater desalination as the target of the article, and now (in the discussion) a complementary source of potable water supply, rainwater collection from rooftops, both seem to be being talked down.

Is this because they are feared, if not immediately obvious, competitive threats to the profitability of the "high tech treatment of sewage" that is being touted as the solution to water supply shortages?

Is it not upon the bargain-basement sequestration of this effluent waste stream that the empire(s) of privatized water supply have, at least in other Australian cities, been planned (out of public view) to be built?

Once seawater desalination becomes a technically mainstream source for potable water supply to urban concentrations of population, perhaps it could, and should, then be made to be the REQUIRED exclusive source for supplying those populations.

As users, those urban populations, or their landlords, would then have to pay the full cost of reticulated supply sourced from seawater desalination. Urban Australia for once paying its dues, at least with respect to supply, even if not yet with respect to disposal.

The article accepts the technical feasibility of desalination. It attempts to attack it on the basis of an implied, relatively unquantified, environmental impact of the imposed energy demand. This is really where the author shows either her lack of having done the most elementary journalistic research into seawater desalination, or her bias against this as a workable solution. OLO itself could have provided many useful insights into possible solutions, but probably little joy for the would-be privatizers of water supply.

The Australian public already owns a key to seawater desalination. It exists in the waste heat from our coal-fired electricity generation, a generating capacity that is not about to be shut down in the near future. Not only can the waste heat be used to desalinate sufficient water to solve the supply problem, but also to provide an accumulating basis for changing over to solar powered electricity generation within the projected lives of existing thermal power stations. See: http://forum.onlineopinion.com.au/thread.asp?article=5616#75523

Forrest Gumpp: Yes.

It’s no secret. Mr Howard and Mr Turnbull have been forthright in their support for sewerage recycling for potable use. Whether this is conducted by big business or big government is a separate question. However, last week, the NSW Government announced it was reserving the ability to sell Sydney’s desalination plant to private interests at any time. NSW Government policy, obviously, is to support privatisation of additional forms of water supply. The Victorian Government is yet to decide between three financing models for their desalination plant. The fact that a fully private model is one of the options indicates that privatisation is consistent with Victorian Government policy.

Politicians do not support private water supply at the household level. The community does. The missing link is to make tank rainwater affordable. Technology developed for this purpose, and discussed in my posts above, makes rainwater a lower cost than desalinated seawater or recycled sewerage.

Liberal Party policy is that the water that falls on a person’s roof in Australia is vested in Government. Clause 2 of the National Water Initiative Agreement (NWIA) explicitly states this. The Federal ALP is mute on the matter. So too are Greens and Democrats.

The National Water Commission asserts that Governments have the right to impose entitlement regimes on the use of rainwater tanks, on grounds that the water is vested in Government.

Clause 2 of the NWIA does not apply to tank rainwater in Victoria, NSW and Queensland, even though those States are signatories.

This week I wrote to the Premiers of NSW, Victoria and Queensland seeking their confirmation of previous advice that the water that falls on a person’s roof in their State is the property of that person.

Recycled water from the laundry generates about the same volume of water used for toilet flushing. The combination of rainwater tanks and recycled rainwater can supply about 50% of an average household’s indoor water consumption. When mains water is recycled for toilet flushing (because rainwater tanks are empty) this is a further 20%.

Any problems so far?

Greg Cameron

-Original Message-
From: Greg Cameron
Sent: Thursday, 8 March 2007 1:02 PM
To: Hon Morris Iemma
Cc: Hon Malcolm Turnbull; Anthony Albanese
Subject: Entitlement Regime For Rainwater

Hon Morris Iemma MP
Premier of NSW
NSWLabor@nswalp.com

Dear Mr Iemma,

Re: Entitlement Regime For Rainwater

Does Labor support the Federal government’s proposed “entitlement regime” for a person’s use of rainwater?

As you are aware, the Federal government proposes an entitlement regime if rainwater tanks are adopted on a large scale “such that their existence impacts significantly on the integrated water cycle”.

Rainwater is an economic source of water supply, particularly when tanks are used on a large scale. Maximum contribution to the state’s water supply will occur, obviously, when rainwater is collected from the roof of every building, and my understanding is that your government, if re-elected, would encourage every building owner in NSW to collect and use rainwater from their roof.

By artificially increasing the cost of rainwater per kilolitre used, an entitlement regime will make rainwater tanks uneconomic compared with other sources of water, such as mains water, desalinated seawater and recycled water. This would deter building owners from using rainwater.

Government imposition of an entitlement regime could only occur if rights to water that falls on a person’s roof in NSW are the state’s water rights.

According to the Federal government, rights to water that falls on a person’s roof in NSW are vested in the government, and roofwater is not the property of that person. However, the Federal government is unable to support its claim because section 392 of the NSW Water Management Act 2000 limits the state’s water rights to water occurring naturally on or below the surface of the ground, and a person’s roof is not the surface of the ground.

Therefore, is it Labor’s position that rights to water that falls on a person’s roof in NSW are not the state’s water rights?

As you are aware, in Victoria, water that falls on a person’s roof is the property of that person, and Labor supports this position.

Yours faithfully,

Greg Cameron