Rain can't drown climate truth


'Water' by Chris JohnstonTwo creeks that were bone-dry for years are flowing again across my hilly bush block. The dams on properties upstream have filled to overflowing, and natural springs in the hillsides have opened again. After so much recent rain, the land feels like a big wet sponge.

Down the hill in the Burra Valley, fat merinos graze in lush pastures. I haven't seen the valley look so green since the 1970s. Canberra's nearby city water dams, which were 30 per cent full three years ago, are now 90 per cent full. With ample water has come a new sense of peace and security across our region.

I wish I could say this is an end to drought and water scarcity in the Murray-Darling Basin, where I live. But the science tells otherwise.

Southern Australia is an area of high natural rainfall variability, irrespective of climate change. These variations are caused by the El Nino/La Nina southern ocean oscillation, and the Indian Ocean dipole. Similar temperate-zone regions of high rainfall variability over irregular periods of a few years are in southern Africa, southwest USA, the Mediterranean rim, and northern China.

All these areas require water storage systems (dams, wells, bores, irrigation systems) for safe agriculture that can help protect farmers from the variability.

As a result of the past two good 'La Nina' years of better rainfall, the Murray-Darling system has started flowing again all the way to the Coorong Lakes at its mouth. Wetlands are refilling and the basin's subsurface reservoirs are being replenished.

But climate change has not gone away. Rising greenhouse gas concentrations continue to heat the atmosphere, causing increased weather extremes, and changes to climate zones: the tropical zone expands, the polar zone shrinks, and the temperate zone in between moves polewards.

We see this in Australia: less rain is falling in southwest Australia and the southern parts of the Murray-Darling basin, less snow is falling in the highlands, but there is more tropical cyclone-influenced rain in the far north of the basin and even in the Lake Eyre catchment in southwest Queensland.

It takes expert statistical analysis to disentangle southern Australia's highly variable rainfall oscillation from the secular climate change trend of increased heat energy leading to changed weather patterns. But the existence of such a climate change trend is clear to expert statisticians who study the weather.

The trend is being masked at the moment by the physical manifestations of a few good years of better rainfall. There is more scope for wishful thinking and misreading of statistics by climate change deniers.

But I prefer to trust the recent publications of the CSIRO and the Bureau of Meteorology on climate change. We know from these reliable sources that the bad El Nino years of drought will necessarily return, and that they will be worse than before when they do because of the climate change trend.

There are also rising demands for limited supplies of water. Due to economic development and larger, more affluent populations, Australian society is now pushing up against water supply risk thresholds in ways that we were not doing in the great postwar era of dam-building.

Nowadays, in years of water scarcity, the large irrigation storage dams in the Murray-Darling basin must be drawn down much further than they were designed for. When these dams were being built, the reasonable expectation was that once filled, they could stay pretty much near full. Tourism and recreation facilities sprung up around their shores based on this assumption.

Yet by the end of the last drought cycle, these huge irrigation reservoirs were approaching empty, because of the years of drought, the declining rainfall and increased evaporation due to climate change, the much greater demands being put on stored capacity by expanded irrigated agriculture, and significant reductions in catchment area runoff.

Expanded irrigated feedlots and water-hungry crops like cotton and rice increase demand for the basin's water. Runoff from catchment areas declines as these areas become more densely settled. More small-to-medium farms means more dams, water conservation earthworks, bores, cropping — all reducing runoff into major dams. More newly planted forestry plantations means less water runoff.

Some of our major irrigation dams are still a long way from refilled. Some may never refill completely. From now on, they are going to have to be managed at a higher risk level, allowing them to run right down again in El Nino years.

Outside the basin, our big coastal cities are using more water too. Even before factoring in climate change, the water stored in good years in dams like Eildon and Warragamba now gets used up a lot faster in dry years than it used to.

There is much less margin of safety in city water supply dams now, which is why desalination plants have to be commissioned in Sydney and Melbourne despite their high cost. Melbourne is even planning to draw water out of the Murray-Darling basin when needed.

There is more rain falling for now, but we cannot be lulled into complacency over water supply.

Australians rightly rejoice in the good years our farmers are having after so many bad years. We can pray they get a few more good years, to strengthen their financial security before the next El Nino phase hits. But farming in southern Australia continues to be a high-risk business and lifestyle. The main constraint on its economic viability and environmental sustainability is the scarce and unreliable supply of water.

Climate change is inevitably going to make it harder to sustain all kinds of agriculture-based human settlement in inland southern Australia. There will have to be more efficiency in water reticulation from storages to farm gates (our farmers are already pretty efficient in the ways they use water), and movement away from heavy water-demanding crops to more water-frugal farming.

As I have argued previously, such reforms in irrigation water use should be managed according to principles of social justice and the public responsibility to sustain vulnerable human communities.

If this means building more dams and water transfer engineering works to bring more water into the basin, Australia should not flinch from this. We are going to need these extra water storage and transfer capacities when climate change starts to hit hard in two or three decades in any case.

Tony KevinTony Kevin is the author of Crunch Time, a book exploring Australia's inadequate policy responses to the climate change crisis.

Topic tags: Tony Kevin, water, drought, climate change



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Existing comments

Thanks for this, Tony.

Southern and central MDB has been dependent on winter rainfall conveyed on mid-latitude westerlies (as has SW WA).

With climate change, these westerlies no longer come as far north as they once did. In an interview with Alexandra de Blas broadcast on Radio National's Science Show on 13 November 2010, U of Arizona's Joellen Russell reports that mid-latitude westerly bands have moved poleward over the observed period (~century or so).

In the northern hemisphere, this shift has been by around 4 degrees of latitude (~450 km), and in the southern hemisphere it's been around 6 degrees of latitude (~670 km).

To put this in context, Wagga Wagga is about 6 degrees of latitude south of Moree.
David Arthur | 22 November 2010

A few years ago I undertook a study trip along the River Murray and Darling to see fist hand how water is used. I was amazed about the massive water waste in agriculture. I noted flood irrigation of unimproved pastures and the use of sprinklers during days when temperatures were above 40 degrees. We still grow rice in arid inland areas to sell it in competition to rice farmers in poor regions of Asia. We seem to subsidise agriculture and waste water resources to enhance poverty in Asian countries. A lot of Horticulture and Agriculture in Australia was developed due to heavy subsidies, cheap land and water and a strong desire to “develop our bush”. Billions of Dollars have been taken away from taxpayers and ratepayers in many States to “rescue the River Murray”. In fact most of the monies have been wasted on studies similar in importance to the re-inventions of the wheel. It remains unlikely that any real action aver will eventuate.

The Realpolitik in Australia provides rewards for political inaction and procrastination but would punish anybody willing to work towards a more sustainable water use. The Green may have been a political party with a genuine environmental agenda a long time ago, but have become full engaged in fighting old issues of the former ultra left of Labor.
Beat Odermatt | 22 November 2010

Thanks for this. I wonder why none of the commentators have considered the LACK of rain in the Western areas of the country. WA has had an extremely dry winter and temperature of 40C already for this Spring/Summer! Is no-
one OVER there interested in anything but our minerals.!
Rosemary Keenan Gwelup WA | 22 November 2010

ROSEMARY KEENAN GWELUP WA wonders why commentators disregard the problems that WA has, and quite rightly so.

WA is suffering the same shift in mid-latitude rain-bearing westerlies as is the MDB, which my comment notes.

The difference between MDB and southern WA is, whereas there are ameliorating alternatives for the MDB, when the rain bamds move south off Cape Leeuwin, there are whole communities and ecosystems that have no backup, nowhere to go and no water to drink.
David Arthur | 23 November 2010

Nice to hear the difference between weather and climate. I'm amazed by the cultivation of rice and cotton in Australia with a few SHF (Sydney Harboursfull) of water kept for this purpose while the MDB dies, especially at the river mouth.
Jenny Martin | 26 November 2010

What should we can we do about “climate change”? The only truth is the fact that the climate has changed and always will change with or without human intervention. Australia has a great potential to act as a carbon sink.

In 1990 the former Prime Minister Bob Hawke announced a 1 Billion-Tree programme. The idea was to undertake mass plantings of trees as an environmental imitative. During the Greening Australia “Sowing the Seeds” conference during May 1990 in Adelaide various papers were presented showing methods to increase tree plantings in Australia. Information was also given that by controlling feral rabbits and other feral grazing animals on about 2.5% of Australia’s landmass the equivalent of 1 Billion Trees could become established.

During the last decade, we have noticed the virtual elimination of rabbits across Australia and massive natural regeneration across large areas of Australia. It is possible that Australia has already met a considerable portion of its greenhouse gases reduction targets. If we combine the massive new carbon sink together with improved farming practices such as minimum tillage, Australia may be able to meet all of its obligations without taking punitive action against industries and householders.
We should also keep in mind that Australia’s carbon sink remain active 12 month a year. If we consider the location of most of our power stations, we can assume that most of the carbon dioxide produced is absorbed by actively growing vegetation and warm oceans within less than 50 km. This is in contrast to the situation in the Northern Hemisphere where massive energy demands during winter has no suitable carbon sink in the vicinity. Trees have lost their leaves and the ground is frozen, which means that most of the carbon dioxide has to remain in the atmosphere. The CO2 levels in the atmosphere rise during Northern hemisphere winters and decline during the Northern hemisphere summers.
Beat Odermatt | 26 November 2010


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