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.

- Borrowed time -

"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.

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.

- Enter climate change -

"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.

At the same time, global water demand is projected to increase 55 percent by mid-century, mainly driven by the growth of cities in developing countries.

For Gleick, global warming is already a threat multiplier.

So far, Earth's surface temperature has risen by one degree Celsius (1.8 degrees Fahrenheit), and the odds of meeting the UN goal of capping the rise at "well under" 2 C lengthen each year. Global warming alters wind and humidity, in turn affecting rainfall patterns.

"Climate changes caused by humans are driving changes in our water resources and demands," Gleick told AFP. "As climate change worsens, impacts on water resources will also worsen."

The prospect of empty water pipes haunts other urban areas in climate hot spots.

California has just emerged from a five-year drought, the worst on record. In 2014-15, Sao Paulo's 12 million souls came close to its own "Day Zero". Beijing, New Delhi, Mexico City and Las Vegas are among other cities that have been facing "huge water supply risks for more than a decade", noted Hoekstra.

When climate change really kicks in, large swathes of Africa -- the Sahel, along with its southern and western regions -- will be especially vulnerable.

Currently, only five percent of the continent's agriculture is irrigated, leaving its population highly vulnerable to shifting weather patterns.

Two-thirds of Africans could be living under water stress within a decade, according to the World Water Council.

For Cape Town, drought conditions may be a taste of things to come.

"Our new normal, at least when it comes to rainfall, is that the chance of dry years increases as we go forward toward the end of the century, and the chance of wet years decreases," said Piotr Wolski, a hydro-climatologist at the University of Cape Town who had compiled data going back more than a century.

Water: Why the taps run dry
Paris (AFP) Feb 13, 2018 - The world has abundant freshwater but it is unevenly distributed and under increasing pressure, UN agencies say, as highlighted by the severe shortages in Cape Town.

- Water, water 'everywhere' -

More than 97 percent of the planet's water is salty, most of it in the oceans and seas, but there is also a good supply of freshwater.

Every year around 42.8 trillion cubic metres (1.02 trillion cubic miles) of renewable freshwater circulates as rain, surface water or groundwater, according to the UN's Food and Agriculture Organization (FAO).

This equals 16,216 litres (34,270 US pints) per person per day -- four times the amount required in the United States, for example, for personal and domestic consumption, industry and agriculture.

Depending on diet and lifestyle, a person needs between 2,000 and 5,000 litres of water a day to produce their food and meet their drinking and sanitation requirements, the FAO says.

About 60 percent of the planet's freshwater reserves is locked in the Antarctic.

Of the rest, more than a quarter is in Central and Latin America, which is 60 times more than that available in the Middle East and North Africa.

"The fact is there is enough water to meet the world's growing needs, but not without dramatically changing the way water is used, managed and shared," the United Nations said in 2015.

"The global water crisis is one of governance."

- Shortages -

In its most recent data (2014), the FAO said 45 countries were experiencing water shortages, defined as less than a thousand cubic metres (one million litres) per person a year. They include South Africa, Cyprus and Morocco.

Twenty-nine of them, including Algeria, Israel or Qatar, were in a situation of extreme shortage with less than 500 m3 per person a year.

A third of the planet's population depends on groundwater and the UN has warned of the danger of overusing these reserves.

Groundwater reserves in part of India's Ganges basin, southern Spain, Italy and California's central valley could be drained dry in decades, it says.

Countries like Canada, Russia and Peru use just one percent of their renewable freshwater.

But others far overuse supply, such as Israel at 261 percent and Bahrain at 8,935 percent.

Countries that use more than their renewable supply draw from nonrenewable underground water or desalinate sea water, as in the case of Bahrain.

- Cities in difficulty -

Freetown, La Paz and Ouagadougou in 2016 suffered severe water shortages following drought, much as Cape Town is today.

The global use of freshwater doubled between 1964 and 2014 because of population growth, urbanisation, industrialisation and increased production and consumption, the UN says.

The demand for water in cities is expected to grow by 50 percent by 2030.

"Water scarcity, exacerbated by climate change, could cost some regions up to six percent of their GDP, spur migration, and spark conflict," the World Bank said in 2016.

- Thirsty farming -

Farming is the single biggest consumer of water globally (70 percent), most of it for irrigation. Industry uses 19 percent and households 11 percent, according to the FAO.

But there are wide disparities at the regional level. In South Asia agriculture accounts for 91 percent of water use, against only seven percent in homes and two percent in industry.

In the European Union and North America, however, industry consumes more than half of freshwater supply, ahead of agriculture (under 34 percent) and domestic use (under 18 percent).

- Global warming -

The UN's climate science panel, the IPCC, said in a 2014 report that for every degree Celsius (1.8 degrees Fahrenheit) of global warming, about seven percent of the world's population will see a drop of at least 20 percent in renewable water resources.

Scientists calculate the planet has already warmed one degree Celsius (1.8 degrees Fahrenheit) since the Industrial Revolution kickstarted the spewing of man-made, planet-heating gases into the atmosphere.

The IPCC projects more frequent and severe droughts in already dry regions, reducing surface water and groundwater stocks. The impact will depend on the level of warming.

SOURCES: AFP, American Geophysical Union (AGU) conference (2016), FAO, Intergovernmental Panel on Climate Change (IPCC), UN-Water, World Bank.

The World Bank advises that data on water should be treated with caution given variations in national collection methods and seasonal and annual sampling.

Related Links
Water News - Science, Technology and Politics

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Aerial imagery gives insight into water trends
Logan UT (SPX) Feb 12, 2018
With an ever-growing human population and its inherent demand for water, there is a critical need to monitor water resources. New technology could make it more feasible than ever to measure changes in the water flow of rivers. Tyler King and Bethany Neilson, researchers at Utah State University, have developed a new method to estimate river discharge using aerial imagery gathered from helicopters and drones. Their new study, published Feb. 7 in Water Resources Research, found that aerial imaging c ... read more