Wednesday, February 14, 2018

Climate may be last straw

AFP, Paris :
Before man-made climate change kicked in-and well before "Day Zero" in Cape Town, where taps may run dry in early May-the global water crisis was upon us.
Freshwater resources were already badly stressed before heat-trapping carbon emissions from fossil fuels began to warm Earth's surface and affect rainfall.
In some countries, major rivers-diverted, dammed or over-exploited-no longer reach the sea. Aquifers millennia in the making are being sucked dry. Pollution in many forms is tainting water above ground and below.
Cape Town, though, was not especially beset by any of these problems. Indeed, in 2014 the half-dozen reservoirs that served the South African city's four million people brimmed with rainwater.
But that was before a record-breaking, three-year, once-every-three-centuries drought reduced them to a quarter capacity or less. Today, Capetonians are restricted to 50 litres a day (13.2 US gallons) -- less than runs down the drain when the average American takes a shower.
Climate scientists foretold trouble, but it arrived ahead of schedule, said Helen Zille, premier of the Western Cape province. "Climate change was to have hit us in 2025," she told a local news outlet.
"The South Africa Weather Services have told me that their models don't work any more."
Worldwide, the water crises hydra has been quietly growing for decades.
Since 2015, the World Economic Forum's annual Global Risk Report has consistently ranked "water crises" as among the global threats with the greatest potential impact-above natural disasters, mass migration and cyberattacks.
"Across the densely-populated Indo-Gangetic Plain"-home to more than 600 million people in India, Pakistan and Bangladesh-"groundwater is being pumped out at an unsustainable and terrifying rate," said Graham Cogley, a professor emeritus at Trent University in Ontario Canada.
More than half the water in the same basin is undrinkable and unusable for irrigation due to elevated salt and arsenic levels, according to a recent study. Cape Town water crisis
Water storage levels in the major dams supplying Cape Town. The city faces a water crisis due to drought.
Groundwater provides drinking water to at least half of humanity, and accounts for more than 40 percent of water used for irrigation. But underground aquifers do not fill up swiftly, as a reservoir does after a heavy rain. Their spongy rock can take centuries to fully recharge, which makes them a non-renewable resource on a human timescale. As a result, many of the world's regions have passed the threshold that Peter Gleick, president-emeritus of the Pacific Institute and author of "The World's Water," has called "peak water".
"Today people live in places where we are effectively using all the available renewable water, or, even worse, living on borrowed time by overpumping non-renewable ground water," he told AFP.
Exhausted groundwater supplies also cause land to subside, and allow-in coastal regions-saltwater to seep into the water table. Dozens of mega-cities, rich and poor, are sinking: Jakarta, Mexico City, Tokyo and dozens of cities in China, including Tianjin, Beijing and Shanghai have all dropped by a couple of metres over the last century. "Half a billion people in the world face severe scarcity all year round," said Arjen Hoekstra, a water management expert at the University of Twente in the Netherlands.
More than one in three live in India, with another 73 million in Pakistan, 27 million in Egypt, 20 million in Mexico, 20 million in Saudi Arabia and 18 million in war-torn Yemen, he calculated in a recent study.
"Global warming comes on top of all this," said Hoekstra.
For each degree of global warming, about seven percent of the world's population-half-a-billion people-will have 20 percent less freshwater, the UN's climate science panel has concluded.
By 2030, the world will face a 40-percent water deficit if climate change continues unchecked.
Glaciers in the Himalayas and Andes upon which half-a-billion people depend are rapidly retreating.