The ABS predicts Australia’s population will increase by 5 million and reach 25 million people in 2032. This represents a 25% increase in the population of Australia.

The Victorian Government has set a mains drinking water consumption target of 326 litres per person per day by 2020. This is a 30% reduction compared with the 1990’s average. Well done Mr Thwaites.

If 5 million more Australians each use 326 litres per day of drinking water, this is 595GL a year in 2032.

In 2001, there were 5.3 million separate houses (75% of dwellings) in Australia and by 2032 there should be 6.6 million separate houses. If 6.6 million separate houses each yields 70KL of rainwater a year, this will be 460GL or 80% of the water needs of 5 million more Australians in 2032. 70KL/house is achievable using technology for alternating between rainwater supply and mains supply at full mains pressure, and capturing rainwater from all downpipes using small tanks that are linked.

If all buildings in Australia – residential, commercial and industrial – each replaces mains water with rainwater, this could be adequate to meet all of the needs of another 5 million Australians (595GL/yr) in 2032.

The cost of installing a 5KL rainwater supply system yielding 70KL in every house in Australia is $2,750 (incl. GST) per house. Maintenance cost is $900 over 30 years. The total cost excluding interest is $3,650 or $1.75 per kilolitre. When the installation cost is capitalised, the operating cost is $0.43 per kilolitre.

The installation cost can be capitalised as a building cost (similar to mains drinking water charges) by making 30% reduction in mains drinking water consumption compulsory at point of sale of every building, with the installation of 5KL rainwater supply deemed to comply for a separate house.

Their ownership of mains water means that State Governments can mandate reduced mains drinking water consumption for all buildings, whereby the voluntary use of rainwater (which is owned by the building owner) is a deemed to comply solution. Why do the State and Federal Governments dismiss this option?

Good piece, except fot the old chestnut, "Household water ..9% of total water use in Australia, ..67% used in agriculture. The rice industry uses almost as much as all Australian households combined (about four times the volume of Sydney Harbour), dairy and cotton use far more. Much .. agricultural production is exported - a virtual trade of thousands of gigalitres of water shipped overseas. Such industries support important regional economies but this international trade has come at the expense of the health of our rivers."

The implication that the water used by agriculture is exported is false, misleading and intellectually sloppy. The vast area of irrigated land transpires moisture at up to 6 mm each day and is redistributed as both rain and dew right over the rest of the country. And this is generally over and above the natural evapotranspiration level and it produces increased volumes and frequency of water cycling.

In this context, fresh water that flows to the sea achieves only a small part of it's real potential. It does provide a valuable ecological service along the way but 99.9% of this service is delivered upstream from the point where it meets the saltwater.

Estuarine species can move from fresh to salt water and back so there is no sound ecological reason why fresh water cannot be captured before it meets the saltwater for subsequent multiple cycling.

There is no reason why the water that was returned to the Snowy River could not be captured after it has done it's work restoring the river to health. It could be pumped from there to Melbourne and this would enable the existing Melbourne water storage to be diverted back to the Murray to restore flows and restore farm allocations in a win, win, win for the tripple bottom line.

Instead, we have proposals to desalinate pure sea water at excessive cost while only mildly brackish water, that could be desalinated at a fraction of the cost, is ignored at river mouths all along the coast. And this is the clever country?

When the professor mentions the appalling state of our rivers, it would be helpful if he acknowledged the fact that in NSW mining under, or too close to, rivers has been a major cause of pollution and water loss in this State. This is thanks to a reckless and irresponsible approvals procedure for mine developments, in which deliberations are held in secret, and which has allowed several major rivers in NSW to be irreparably cracked and polluted. Remediation is not monitored or enforced, and anyway is not highly successful in the very few places where cracks have been grouted up. With the escalating profits and royalties from coal, several more rivers are under threat right now. The upper Hawkesbury-Nepean Catchment is being progressively desiccated, with dozens of creeks and streams undermined and with cracking of the Nepean and major tributaries like the Cataract and Bargo Rivers continuing apace. When are academics going to come to the help of community groups round the state which are attempting to highlight this issue ? With the ongoing wrecking of our rivers often in beautiful but inaccessible gorges, it's a case of out of sight, out of mind. But at the very least, the water loss involved when rivers are cracked in thousands of places should warrant a little attention.

“Unfortunately, changing behaviour alone will not be enough in the face of a rapidly growing population and increased uncertainty of supply as a result of climate change.”

Thankyou Stuart Bunn for acknowledging that continuous population growth is a major part of this issue.

This is rare in such articles, and I have been very critical on a number of occasions on OLO about the lack of even a mention of increasing population pressure.

However, you then go on to discuss many ways in which we can improve water-use efficiency while not even touching on what we can do about population growth. In omitting this, you are emitting half of the problem and half of the solution, or worse – actually facilitating ever-larger populations by way of reducing per-capita water usage, so that more and more people can be squeezed in under the same water resources, thus condemning us to not finding a solution.

As untenable as it might seem, issues such high immigration and transmigration into regions with water-supply issues have GOT to be discussed openly – as openly as the things that you do mention.

At the national scale, urban dwellers aren’t the real water guzzlers. Household water consumption accounts for only 9 per cent of the total water use in Australia, compared with 67 per cent used in agriculture. The rice industry alone uses almost as much as all Australian households combined . (SO WHAT)

Much of this agricultural production is exported - a virtual trade of thousands of gigalitres of water shipped overseas. Such industries support important regional economies but this international trade has come at the expense of the health of our rivers. (Don't ya just hate those capitalist rice cockys )

The real water crisis in Australia is that we have yet to come to appreciate the true value of our freshwater assets. ( Too right Stuart )

Aust rice production 1.3 million tonnes

moistue content dried rice approx 14% = 182 megalitre (meg)

85% exported = 155 meg per/anum

@ $400m export value = $2.58 mil per meg

Or $2.58 p/litre for water contained in rice exported

Not quite thousands of gigalitres . Anyway what's the price of treated drinking water supplied under pressure to the kitchen tapp ?

So who doesn't understand the value of water ?

I think perhaps the fastest growing sector of our natural resource reliant industries would have to be the regulation industry .

Working tirelessly to keep the myth alive lest all the wonderfull funding might dry up .