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How to be the worst dinner party guest – respond to the Murray Darling

I have been to several small dinner parties since the ABC Four Corners report. I have been challenged with the same statements at each of them.

‘Cotton farming should be banned?’

‘Shouldn’t we be growing food or something?’

‘That water would have kept the Murray mouth open’

It is a difficult to explain the complexity of the Murray Darling Basin in one headline, or even in one Four Corners show. It also hard to explain the complexity at a dinner party when passions are high. It isn’t a recipe for a successful dinner party. So I will try here.

Why grow cotton?

The first statement is that cotton farming should be banned. It is interesting that the statement is not ‘irrigation should be banned’. It is singularly focused on cotton – and sometimes rice. Whereas other big irrigators are not in the same category – such as horticulture, wine grapes, dairy, grain and beef. The real question is, ‘why do farmers choose to grow cotton and not crops that are more relevant to the Australian society – such as food and wine?

So let’s have a look at the details. How much do all the crops use and what value do they create?

These figures change with each season. Like all crops, the co-efficient of variation is wide. Cotton uses about 8Ml/Ha. Cotton ranges from about 3Ml/Ha in places like the Upper Namoi, to up to 12Ml/Ha in a particularly dry season in the hotter regions of the industry.

Corn, or maize uses about 10Ml/Ha with a similar range.

Wine grapes uses about 6Ml/Ha and vary from about 2Ml/Ha in high rainfall areas to 8Ml in dryer regions.

Lucerne uses about 6Ml/Ha.

Rice uses about 12Ml/Ha.

Dairy about 6Ml/Ha. And so on.

Almonds, citrus and other trees uses about 8Ml/Ha. The size of the tree and the rainfall determines water use

Cotton is about mid-range in that sample of summer crops. However, the returns are the real question. Cotton returns nearly the most money to the economy on a per Megalitre basis. The farmer has the right to use the public asset of water, and they have a duty to create as much value as they can. They have that duty to the public, to their communities, families and bankers.

Cotton has, over the past 20 years, doubled its water use efficiency. Those farmers are now producing about twice as much cotton with each megalitre. Those farmers are by far, the highest yielding cotton farmers in the world – the nearest being Israel who are small volume producers.

Simply put, for each megalitre of water, cotton returns nearly the most value to the economy, community, families, business and bankers.

You will notice that I said ‘nearly the most returns per megalitre’. There are crops that probably produce more dollars for each megalitre. Those are often horticultural crops such as vegetables, and tree crops such as citrus, almonds and walnuts.

So, why don’t we just grow vegetables?

Transport. There is only one answer. We have a very small domestic market of 24 million people and it doesn’t take a lot of vegetables to over supply that market. So we have to export. We would have to export a perishable product. It is a long way to our markets. China is at best 10 days by sea freight. Most perishable products have begun to devalue by then.

The other alternative is air freight.

I was involved in the first flights of fresh milk from Sydney to Shanghai. It was a great thing but it was very difficult. It took us a year to get the approval and then we had to sell it at more than $6/litre to make it worthwhile. To this day there are still only small shipments of fresh milk into China. Many will talk about wanting to pay $6/litre for fresh Aussie milk, but few will actually put their hands in their pockets and make the purchase.

Cotton, on the other hand is non-perishable. You can ship and store cotton without the urgency of it loosing value. Sadly, we have thousands of containers going back to Asia every year that are empty. Cotton is a backload that is cheap to ship and easy to handle. It will sit in a warehouse for some years without losing value.

Why don’t we grow tree crops?

So, why don’t we grow tree crops like wine grapes, almonds, walnuts, pecans, citrus and the like?

Tree crops are permanent plantings. They are planted once and stay there for years. The Darling basin is one of the more ephemeral rivers in the world. To have permanent plantings we would need a 100% reliable water supply. On average in some valleys, those crops would die every second year.

The Murray Valley is better suited to tree crops – and mostly, that is where they are.

Cotton is an annual planting that the farmers only plant when they think there is enough water available for the coming season. I was involved in one cotton farm that did not have a water allocation for seven years in a row. That family sat and waited for seven long years.

Those farmers grow cotton because it is the best choice for that region and they are good at it.

What about the mouth of the Murray?

The final question is about the Murray mouth near the town of Goolwa in South Australia. ‘Surely all that water would keep the Murray open!’

This is one of the many misconceptions are friends in South Australia have and they make the most of cementing that notion in the media. It is possible to calculate that closing down the irrigation industry in the Darling Basin would not affect the Murray mouth at all.

Let’s look again at the numbers.

Variously it is estimated that the Darling basin provides about between 17 and 21% of the mean flow of the Murray Darling Basin. That is, four out of each five litres at Wentworth near Mildura come from the Murray and only one comes from the Darling. Easily, it is the lessor portion of the Basin.

The general security water allocations in NSW above the Menindee Lakes are around 800,000Ml. That does sound like a lot of water. It is about one and half Sydney Harbours. However, the Menindee Lakes can evaporate about 800,000Ml each year. (47,500Ha at an average evaporation of 2.4metres is 1,14 million Ml when full). The Menindee Lakes are kept as full as possible with man-made walls to provide water for recreation and for the city of Broken Hill 100kms away and outside of the Darling basin.

Lake Alexandrina near the town of Goolwa is 64,900Ha and evaporates about 1.6 metres of water each year. Annual evaporation can be more than 1 million Megalitres each year. To ensure the evaporation, the people of South Australia installed barrages at the bottom of the lakes to hold the water away from the Murray mouth. Lake Alexandrina was once a tidal estuary and is now a fresh water evaporation pond. The water flowed in and out of the mouth of the Murray for centuries. With the barrages, it can now only flow out.

The much maligned Cubbie Station is about 160 metres above sea-level. That is 1.6 footie fields high. The old AMP centre in Sydney is higher (28 metres). Imagine water falling into the river at Cubbie and going to the Murray mouth. It is about 1,700 kms by road from Dirran to Goolwa. The slope of the land is 1:10,000.

For water to fall into the river at Cubbie, the water has to travel 10kms to fall just one metre. Stand up and hold your hand one metre above the floor. Then pour a litre of water and imagine it moving 10 kilometres from a gradient of only one metre. Imagine doing that on a tin roof. How much water would you need to pour onto that roof to let it go 10kms? Now imagine doing that in a hot, arid region with soil that is highly absorbent. There is little doubt that any of the water that goes past Cubbie Station would have ever made it to the Murray mouth.

In fact, many of the rivers of the Darling basin do not significantly make it to the Darling – except in flood. These could be called terminal rivers. They are the Gwydir, Narran, Condamine, Balonne, Culgoa, Warrego, Macquarie, Castlereagh and the Lachlan. These rivers can run into natural wetlands such as the Macquarie Marsh and the Gwydir Wetland.

The only significant contributions to the Darling flow are the MacIntyre, Barwon and Namoi.

With so few rivers actually contributing and so many losses along the way, the actual impact of water from the Darling at the Murray mouth is close to zero.

At the end of the dinner parties I usually feel like I have been the worst guest by having such a technical discussion around such a convivial setting with so much excellent food. It often surprises me that people do want to understand the complexity of such a dynamic and mysterious river system.

This river system will continue to fascinate and confound us for years to come.

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