Yep, we have the means Sector, but we don't seem to have the will - or are we as a nation too intelligent ?
As Barg points out, desalination plant brine has or creates it's own problems.
Re: a smaller Australia (population wise) who knows. China opted for a smaller China with their ''one child per family program'' It has worked, there are 400 million less Chinese today than there would have been with no program. Incidentally, China does have a big water problem.
Population growth in Australia will soon low down, as predicted by many pundits (including Dick Smith) it has to. The slow down will negatively affect property prices, but who cares, we have had a good run.
