Fester, You seem to think that just because 9% of water use is domestic that the city requires another 91% to function. Whilst the city will draw on the water resources used in food and electricity they do not have to come from the same source. Just as Sydneys power comes from the outside, like the Hunter valley, so does most of its food. This does not impact on the city supply. We have large agricultural surpluses as it is, with potential to do more in the north where the water is. This is where your theory fails, because 70% of water is used in Agriculture, when nearly all demands are met by dryland production(except rice and some milk, friut and veges). Should demand require it new areas for irrigation will open up in the North. You just have to accept that not everything a city requires comes from it's own water supply.

Can I state clearly that I do NOT advocate a city of 10million in the Ord. Nor do I think it remotely likely.

If Sydney uses 635GL/ year then it is likely that such a city would use approximately 1300GL/year. Your period of 6 years of low inflow suggests 2330GL/year,less your figure of evaporation at 1400GL, leaves us with 900 as you say, which is a 400GL shortfall(from my use figure of 1300GL). At this shortfall a half full Lake Argyle will last over 10 years or a full one 20+.

Throw in some recycling and rainwater tanks if you're still unsure.

“Perhaps I should of said pointless instead of stupid”

Alanpoi, that doesn’t make it any less extraordinary. I say again; I can’t imagine a more important discussion than this one.

Why is it so important? Because we obviously cannot support an ever-growing population with anything like our current level of technological competence, profligacy and stressed basic resource base.

So achieving sustainability and thus living within our means with an intact and strong society is the most important thing. Once we have achieved that or are confident that we are on the right track, we can consider further population growth.

But if we don’t chase the sustainability goal with all our fervour, we are bound to suffer economic and social collapse and a much worse quality of life for the vast majority.

We then won’t be in any sort of state to help the less well-off hundreds of millions around the world.

There are fundamental problems with your enormous ‘technofix’ ideas. The primary purpose should surely be to achieve the elusive genuine sustainability paradigm, and certainly NOT to simply accommodate ever-more people.

The biggest problem with technological advances is that most of them lead directly to the facilitation of a larger population. So instead of improving our future outlook, they are making it more precarious!

Let’s have technological advances as fully as we can implement them. But for goodness sake, let’s have population mitigation along with it.

And yes I agree, let’s pull back on the over-the-top profligacy of McMansions and the like and learn to live comfortably but a tad more frugally.

Rojo, you still have electricity and gas to supply the ten million(877 GL), and what about the environmental flows (238 GL)? I like your water tank option but I dont think that it would get you there. What interests me is the potential of new technology to alter the picture. For example, per capita annual energy consumption is estimated at about 76,000 kWh (http://www.eia.doe.gov/). If solar thermal power works as claimed, then over 3 megalitres of freshwater per capita per annum could be produced as a byproduct.And the water would be produced gradually so you would not require huge storage areas.This is well above consumption estimates considering true water usage, let alone your "The food can be grown elsewhere." calculation. You suggest that an increased population is inevitable due to environmental refugees, but if this technology works here it will work worldwide, with the potential to vastly improve the living standards of billions.

Perhaps we can sustain a greater population. Perhaps we can't.

Leaving aside Rojo's unlikely scenario of us being forced to accept large numbers of "environmental refugees" or whatever, my questions are:

--Should we accept large numbers of immigrants?

--How does it benefit us?

Remember that repeating the mantra "Immigration is good" does not make it so. If you want higher immigration, or even immigration at current levels then:

Give us some HARD FACTS.

Spell out both the costs and benefits.

Tell us who benefits and WHO LOSES.

Let's have some honesty and some critical analysis in this debate.

And let's not get caught up in unlikely scenarios of being forced to take in people.

Stephany, I didn't say we would be "forced" to take in "environmental refugees" it was your interpretation that brought up sanctions and invasion. I see it more as a moral obligation from international groups like the UN as we are emitters of greenhouse gas, and as we are a wealthy, developed nation. We also have the necessary untapped resources.

Is it likely? depends on whether or not cimate change is as great as current dire predictions

Fester, excellent points. Solar would be an absolute win-win situation. The Lakes current hydro electric would provide some of the requirements and also deliver the environmental flows at the same time. The region is home to some of the largest tidal fluctuations in the world, 4 times a day. An awesome potential power source. Fresh water use nil.
The Timor sea region has vast gas fields like the Bayu-Undan gas field which delivers gas to Darwin. WA has 80% of Australias tapped gas reserves. Water use?

No comments on the recycling?

I'm don't understand your contempt for growing the "food elsewhere" as we already produce enough for those extra mouths, let alone the potential production from surrounding areas. Our current cities rely on food from elsewhere why couldn't our hypothetical one.

No I didn't say "inevitable" re: environmental refugees