What's the alternative though? Well how about just letting people pay the actual cost of water so that they have an incentive to economise?
When most things get scarce, their price goes up. This sends a signal to consumers to economise and find alternatives and a signal to producers to find new sources and ways to produce them. We don't do this with water though. Instead we subsidise one of our most precious resources - massively. We encourage industrial water users to recycle their water or else use recycled water rather than water we've spent millions making fit for drinking. But why would they when it's so cheap? Cheap because it's subsidised by every taxpayer.
So why don't we do this? According to NSW's Water Minister Nathan Rees, that system "would result in gross inequalities and be a nightmare for business":
Any form of sound business planning would be impossible if water prices fluctuated from month to month and season to season.
The current system isn't too equitable either. Is it equitable that low income earning taxpayers who do their best to save water subsidise big water users to fill their pools and keep their lawns looking lush? In any case the extra revenue from actually charging wealthy water users for the water they use can be used to provide assistance to low income households.
As for the business certainty argument, businesses deal with price fluctuations all the time. I'm sure the cafe downstairs from my work would be happier if coffee bean prices didn't fluctuate, but they don't ask the government to nationalise the coffee trade to deal with it. The prices of rent, employees, petrol, commodities, food and every other business input fluctuate weekly or daily. And if it's critical for a particular business to know the price of water in advance, I'm sure purchasers and suppliers could negotiate to lock in a price in advance for a set period. That's what futures markets do with commodities around the world.
The federal government is putting a price on carbon emissions - a challenging and complicated task that involves working out the emissions from a huge range of business activities and creating new and untested markets. So why can't we allow a realistic price to be placed on one of our most precious resources? The alternative is pouring an extra billion dollars into an environmentally questionable desal plant that we don't really need.