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The Forum > Article Comments > Only a price on water can end threat to food security > Comments

Only a price on water can end threat to food security : Comments

By Colin Chartres, published 24/8/2009

There is a looming global water crisis which climate change will aggravate by making rainfall more erratic in many regions.

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Fractelle

I tend to think more the government is lacking in foresight and creativity. More of the same economic consumption and consumerism mentality (Growth, Growth and more Growth) rather than any genuine discussions about sustainability. Hence the desalination and clean coal initiatives.

However, I agree that political donations should be banned and a whole new system put in place to remove any enticements or influence on major policy whether real or perceived. Particularly after revelations from developers in regards to the NSW State Government and Wollongong Council sagas.
Posted by pelican, Tuesday, 25 August 2009 9:31:44 PM
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Grim -

The water tank arithmetic isn't quite as simple as you show.

First you never get 100% of the runoff going into your tank. If that was the case your roof would be dry the moment the rain stopped. 90% might work.

Second, most houses aren't set up to drain the entire roof to one point. Half or two thirds of the roof is probably a good assumption.

Third, the rain doesn't fall just when you need it like it does out of the tap. If we get 70mm of rain on 100 m2 of roof and 90% runs off that is 6300 Litres. If your tank is smaller than 6300 itres or isn't empty when the rain hits, some of that rainfall will run down the gutter into the stormdrain.

Fourth, If you have a 5000 Litre tank and it doesn't rain for two weeks you still need water.

I'm not saying tanks don't help but you are unlikely to be able to replace all your water needs with a 5000 L tank and a 156 square metre roof.

Also water isn't priced to make the purchase of a tank attractive. If you buy a 5000L tank for $4000, then you have to fill it up 700 times to get your moneysworth out of it. If you use it regularly you might be able to fill it up about 14 times a year. That means it will take 50 years to pay it off. The tank is unlikely to last 50 years. If the price of water continues to go up then this might drop to 40 or 30 years.
Posted by ericc, Wednesday, 26 August 2009 10:17:12 AM
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And if you invest the money it buys a lot of water.
If it is purchased as part of the house then it is on the mortgage so double the cost or more.
Not everyone has the finance to purchase.
Would it not be better if the money was invested in a community venture? One large tank is cheaper to build and uses less resources and reduces green house gases as would be used in the production of tanks, transport and installation.
A lot of water that runs off is not wasted goes into the local stream so others down river benefit thus it is only diverting.
Posted by PeterA, Wednesday, 26 August 2009 4:44:04 PM
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ericc, granted; however...
First, possibly true, however... my water tank is outside my bedroom window, so I know only too well that I get small amounts (drip, drip, drip) of water from condensation, even when it doesn't rain.
Second, houses in my part of the world which rely entirely on rain water, do catch the whole roof. Naturally.
Third, very true. again, if you rely entirely on rain water, you are going to get the largest tanks you can, and they will very rarely be full (I have 2x20,000l tanks). My point was actually to put rainwater tanks back into suburban backyards, and for the government to pay for them, instead of spending the money on dams no one seems to want. It would not be an insuperable engineering challenge to meter tanks hooked into the water grid to be perpetually half full.
That way, flooding rains in Sydney could be ameliorated, and at least some of that flood water could be captured.
I'm thinking along the lines of electricity; 2 way inverters for those with solar panels, so they can draw from the grid, or supply to the grid, according to the circumstances.
This point I hope also answers PeterA's observation.
Posted by Grim, Wednesday, 26 August 2009 5:42:53 PM
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I fail to see how increasing the price of water solves the problem. It suggests that people are wasting it which is certainly no longer the case in Australia. How can poor countries pay more? The problem, which has been outlined by other posters, is overpopulation which is not being addressed at all.
Posted by Atman, Wednesday, 26 August 2009 7:44:52 PM
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Grim: "water from condensation"

You are claiming you get a meaningful amount of water from condensation? You've gotta be kidding me. (I also have a 20,000 L tank.)

I agree ericc's back of the envelope calculations are based on unrealistic assumptions, but by some fluke his conclusions are about right. A household of 4 using 140 L per person uses very roughly 4,000 L per week. I recall some tank proponent saying realistically you need 4 20,000 L tanks - one on each corner of the house. That gives you 20 weeks of water which is about what you need to keep you out of trouble near the coast - so I guess he was right. The tanks are about $3,000 each, so $12,000 in total and we end up roughly were ericc did.

It also turns out that an average 4 bedroom house has 200 m2 of roof. And guess what? In Brisbane that almost exactly equals the amount the household would consume. (Assuming 1200mm/yr, 15% wastage, 4 people in the house using 140 L per person.) http://www.nwc.gov.au/www/html/236-water-use-in-australia.asp http://www.enviro-friendly.com/brisbane-rainfall.shtml The point being you can't loose any to overflow - which is another reason you need 4 tanks.

Anyway, as I said, it is all beside the point. Household's use 11% of Australia's water. http://www.nwc.gov.au/www/html/236-water-use-in-australia.asp So tanks aren't going to solve the water problem described in the article.
Posted by rstuart, Wednesday, 26 August 2009 9:52:35 PM
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