THE planet is far from running out of water, but many countries are beginning to exhaust the local supplies they need to maintain agricultural productivity and ecosystem health.
Welcome to the age of “peak water”.
“Peak oil” describes the peaking in discovery of extractable oil, followed by a decline - a theory that is gaining credibility, with recent forecasts suggesting that the peak could occur sometime between now and 2030.
But international water expert Peter Gleick believes that unsustainable use of water is “far more worrisome, and far more difficult to evaluate”, than limits on resources such as petroleum.
Dr Gleick says that because of water’s ubiquity, “peak water” isn’t the same thing as peak oil, but he believes that it’s a useful phrase to describe the effect humans are having on many critical sources of water.
“I believe that a substantial fraction of the global food supply is produced with unsustainable groundwater use, in regions where peak non-renewable water limits have already been exceeded,” said Dr Gleick, an international water expert and founder of the Pacific Institute in California.
“If we do not figure out how to produce food from renewable and sustainable water resources, the food supply of hundreds of millions of people, or even more, may be at risk.”
Julian Cribb, author of the soon-to-be-released book “The Coming Famine”, said dwindling water resources aside, a major conflict between the water needs of agriculture and cities is emerging.
The world’s irrigated agriculture currently uses about 2500 cubic kilometres of water - 70 per cent of the water used by people - to produce 45 per cent of the world’s food.
Urban areas currently use about 1300 cu km. With a growing population moving towards greater urbanisation, the world’s cities are expected to demand about 2500 cu km by 2050, Mr Cribb.
Freshwater supplies already over-extended, and climate change is melting glaciers and increasing evaporation rates, Mr Cribb said. So where does the extra water come from?
“Urban dwellers are going to have to drink their own,” he suggested.
Peter Gleick wants the world to take greater notice of its current abuses of water.
In some instances, like the Colorado River in the United States or China’s Yellow River, Dr Gleick blames overallocation of water resources by water agencies.
In others--the North China Plain, the Ogallala Aquifer of the American Great Plains and California’s Central Valley aquifers, and “many groundwater basins” in India - Dr Gleick faults unmonitored groundwater pumping.
He divides unsustainable water use into three forms: peak renewable, non-renewable and ecological water.
Of peak renewable water, Dr Gleick said, “Because a particular water source may be renewable, does not mean that it is unlimited.”
The Colorado River is shared by seven US States and Mexico. In most years since 1960, none of the river’s 18 billion cubic metre average annual flow has reached the river delta.
In 1905, when the Colorado’s flow was first recorded, 23 billion cubic metres reached the delta.
Peak non-renewable water generally refers to pumping of “fossil” groundwater that may be hundreds or thousands of years old.
It has been estimated that eight per cent of India’s water use between 2002-08 was from non-renewable aquifers.
Dr Gleick considers peak ecological water - where the benefits of water to humans are outweighed by the damage done in removing water once used for ecological services - to be the most immediate concern for many watersheds.
Humans have been estimated to now use half of the world’s accessible freshwater flows.
“The number of freshwater species has decreased by 50 per cent since 1970, faster than the decline of species on land or in the sea. River deltas are increasingly deprived of flows due to upstream diversions, or receive water heavily contaminated with human and industrial wastes.”
Of all developed nations, Australia is the most acutely aware of the finiteness of fresh water.
In its 2008 “Sustainable Yields” report, CSIRO said that developments in the Murray-Darling Basin had significantly altered the flood regimes supporting the Basin’s wetlands.
The aggregated effect of water extraction had been to reduce flows at the Murray River mouth by 61 per cent, the agency repoted, with no flows going through the mouth 40 per cent of the time compared to one per cent of the time “in the absence of water resource development”.
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