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The Forum > Article Comments > Confronting our water challenge > Comments

Confronting our water challenge : Comments

By Malcolm Turnbull, published 11/8/2006

The simple fact is this: our cities can afford to have as much water as they are prepared to pay for.

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Banjo—

The reason why rainwater tanks are not a significant source of water supply in Goulburn is because NSW Government policy throughout the 20th century was to discourage them. 30% of households outside Sydney have rainwater tanks but only 3% in Sydney.

Now, the Government requires all new houses in NSW to reduce mains drinking water consumption by 40%. The Government considers that installing rainwater tanks in existing houses is too expensive and therefore the law only applies to new houses and major renovations.

However, if all houses were required to reduce mains drinking water consumption by 40% at point of sale, with rainwater tanks deemed to comply, there would be a significant drop in the cost of installing rainwater tanks in new houses. All house owners – new and existing – would benefit.

The cost of supplying, installing and plumbing (including with pressure pump) a 5KL rainwater system for an average house in Goulburn (and NSW), would be under $3,000. Houses are sold on average every seven years. Almost all houses in NSW will change ownership within a decade.

Drought stricken Goulburn is a good case study. Rainfall in the City of Goulburn for the 12 months to 31 July 2006 was 573MM. A 5KL rainwater system would have provided 60KL of water for an average Goulburn house (175m roof area) when used for hot water, laundry, toilet flushing and external uses. As part of the plumbing package, an automatic switching valve is installed for returning the household to mains water the instant the tanks run dry, and back to tank at the next rain event.

Several extreme rainfall events in Goulburn meant that a 5KL rainwater system would have overflowed by about 27KL in the 12-month period. The impact of Goulburn’s level 5 water restrictions is that every person currently uses 150 litres of mains drinking water per day, compared with 380 litres per day in Sydney.

Based on current rainfall and per capita consumption, rainwater tanks would have supplied 40% of Goulburn’s drinking water needs in the last 12 months of record-breaking drought.

Greg Cameron
Posted by GC, Monday, 21 August 2006 9:19:19 AM
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Greg,
Am pleased that you have included a presure pump and automatic switching valve in your costings. However, even if Government legislated for each house to have a system as you advocate, I doubt if a 40% reduction in mains water use would be acheived.

I don't wish to pour cold water on the use of house tanks but the flaw is that, for areas with a normal dry summer, your system is at its lowest usefulnes at the period of greatest need. I submit that in these areas the summer requirements far outweight the winter needs.

I have not watered outside since March but come November I expect to, and right through to next March/April (which is normal). I have a useable garden water storage of 300KL and many summers this is not sufficient to get through, watering 600sq m. Just to green survival stage.

I expect your 5KL tank would not see a week out watering 200sq m.
It would last 3 weeks only for a house with 4 persons.

The storage needs to be increased dramaticly and I acknowledge that this increases the capital costs, but I see no way of avoiding this if the system is to be of practical use.

Summer rainfall areas are an entirely differnt situation.
Posted by Banjo, Monday, 21 August 2006 2:11:39 PM
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[Deleted for lack of relevance. Try the general forum if you want to start your own thread.]
Posted by KAEP, Monday, 21 August 2006 8:24:01 PM
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Funguy,

Thanks for the compliment.

I think your grammar is a bit shaky but I love the vocab and the sentiment. Keep posting.

And remember: We don't have to hang them. If we scuttle Howard's Sydney immigration funnel, we stop Sydney's water shortage. And go a long way to easing the NSW drought in the bargain. Its all we have to do.

And ... more immigrants in Sydney means NSW returns more GST to Canberra and the more GST Canberra gets, the bigger percentage it will want to keep.
Res Ipsa Loqitur, Immigration is not in NSW's interest.
NSW has done our bit for immigration and a lot more to boot. Its over to the other states now!

You got room for more in SA, Funguy?
Posted by KAEP, Monday, 21 August 2006 8:53:45 PM
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Bango makes some constructive points about yield of water from rainwater tanks that are worth addressing.

He says “I don't wish to pour cold water on the use of house tanks but the flaw is that, for areas with a normal dry summer, your system is at its lowest usefulness at the period of greatest need. I submit that in these areas the summer requirements far outweigh the winter needs”.

The key point here is that rainwater tanks perform when there is rain. Roofs are impervious surfaces and so they generate 100% runoff of water. In the wet season (winter in the NSW Tablelands) the time not to use mains water is when it rains and the dam catchments are producing maximum water runoff because the soil has its highest moisture content for the year. In summer, rainfall on a dry catchment produces much less runoff into the dams per mm of rainfall. During the summer dry, when rainwater tanks are empty, the mains water that was not used in the winter can be used. In other words, dams provide a back-up supply for the rainwater tank in summer.

Of course, the flaw in this argument, so far as Banjo’s garden is concerned, is that the NSW Government wants there to be a net reduction in mains drinking water consumption by the substitution of rainwater, and watering restrictions prevent a person from using in summer the mains water that they saved in winter.

There is still rainfall in Goulburn, even in the current record breaking drought. In the 12 months to 31 July 2006, there was 573mm rainfall that would have yielded 60Kl of water for an average Goulburn house from a 5KL rainwater supply (see my posting above). More storage would not have produced a significantly higher volume of water from a house roof .

Greg Cameron
Posted by GC, Wednesday, 23 August 2006 10:58:16 AM
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Greg and Perseus
I believe that the 175sq m roof catchment to be about average and the 13500 storage to be the minumum for those areas with summer rainfall.
This would make a substantial difference to the mains water requirements for each house. Even in the 'dry' months at Logan there is sufficient rainfall to make use of the system.
The areas that have wet summers,i.e. from east coast to the escarpment is the area you should concentrate your efforts. It is also the area of highest population.

I continue to question the economics and practical use of the same system in areas that normally have dry summers. The storage would have to be increased substancially.

Some Sydney people have expressed concerns about the quality of rainwater caught off their roofs because of air pollution residues on the roofs. Is this a concern and if so is there a way around it?

Ludwig.
I agree with you about the immigration factor. Simply put, more people require more water as well as other inferstructure. Both Liberal and Labor are in the hip pockets of big business who want high immigration and neither Liberal or Labor have a population policy. The reason being that they can play politics with various ethnic groups before elections, promising increased access for their relatives and so on. We need to determine our carrying capacity before setting immigration to suit.
Posted by Banjo, Saturday, 26 August 2006 12:44:27 PM
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