Psssst. Don't mention population.

If there were a price on water used for growing rice and cotton, would famers grow those crops, or would they use water more efficiently to produce more profitable crops?

Many farmers are to be applauded for improving the efficiency of water use but no one should be fooled into believing that there is no further room for improving the way in which water is used or stored.

The problem facing the Murray-Darling basin is not the use of dams to regulate the flow of water to the sea but the allocation of that water which exceeds available flow and for this reason is unsustainable.

The availability of that flow is of course dependent on how much it rains over the basins catchment area and of course the rate of evaporation, both of which are influenced by climate change.

Climate change is largely induced by human activity and is responsible for drier conditions becoming more prevalent over the southern half of Australia and for higher temperatures, the latter expected to increase evaporation of surface water.

Without international agreement among major greenhouse gas emitters to reduce their emissions and have those reductions policed, significant climate change will occur.

Action to limit evaporation and use water more efficiently is open to us and must be taken if Australia is to remain largely self-sufficient in food production and a net food exporter.

However, these are stop-gap measures which will not provide a long-term solution to the practices which are responsible for making them necessary, climate change which, if allowed to continue, will permanently reduce availability of water in the southern part of the continent.

"If there were a price on water used for growing rice and cotton, would famers grow those crops, or would they use water more efficiently to produce more profitable crops?" asks Agnostic.

The economically rational thing would be to grow less food and fibre - and more wine.

That would give fresh nuance to the claim that Australia is 'girt by sea and pissed by lunchtime...'

Agnostic of M, Water isn't free, it has a usage cost payable to govt, it has a pumping and distribution cost and it has an opportunity cost for those idle billions tied up in entitlements.

Water in cotton country regularly exceeds $250 per ML for temporary trade and did so recently. Much more than the $55 per ML in Murray.

Water is the key driver of my business and the best return using my allocation is to grow cotton. I could try growing vegies but would flood the market. I could irrigate wheat but would need to develop twice the acreage and get half the return.
Criticise allocations if you choose but to suggest farmers shouldn't grow the most productive crops they can, with the water to which they are entitled, is just poor thinking. Don't worry you're not alone, it's a common mistake.

JulianC, I hear a lot of grapes have gone unharvested in the last few years. Good return on the water there.

There is also a price on water for rice. And rice growers get the lowest security water, so it is only available to them in years when there is relatively more of it.

Highest security water apparently goes to orchardists, because you can't decide not to grow your peaches this year and do it next instead, as you can with grasses like rice.

I think the poor old rice growers get a bit of a bums rush in this as well.

I'm afraid building more dams is not the answer.
VK3AUU,
I think you're right on this. Evaporation, the influx of pest fauna due to more water, recreation and so on are some of the negative effects of dams. In my view recharging the groundwater is a far more sensible tactic.