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How does a city run out of water?



THE world has abundant freshwater but it is unevenly distributed and under increasing pressure.

As such, parts of the world are in real danger of running out of water, as highlighted by the severe shortages in Cape Town right now.

South Africa on Tuesday declared a “national disaster” over a drought that has ravaged parts of the country and threatened to leave the city without domestic tap water.

So how does such a thing happen?

WATER, WATER ‘EVERYWHERE’

More than 97 per cent 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 of renewable freshwater circulates as rain, surface water or groundwater, according to the UN’s Food and Agriculture Organisation (FAO).

That equals 16,216 litres 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 2000 and 5000 litres of water a day to produce their food and meet their drinking and sanitation requirements, the FAO says.

About 60 per cent 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.”

As such, governments are being urged to act and ensure efficient water sharing agreements and infrastructure are in place.

SHORTAGES

In its most recent data from a few years ago, 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 cubic metres 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 parts 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 1 per cent of their renewable freshwater.

But others far overuse supply, such as Israel at 261 per cent and Bahrain at 8935 per cent.

Countries that use more than their renewable supply draw from non-renewable 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 per cent by 2030.

“Water scarcity, exacerbated by climate change, could cost some regions up to 6 per cent 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 per cent), most of it for irrigation. Industry uses 19 per cent and households 11 per cent, according to the FAO.

But there are wide disparities at the regional level. In South Asia, agriculture accounts for 91 per cent of water use, against only 7 per cent in homes and 2 per cent in industry.

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

GLOBAL WARMING

The UN’s climate science panel, the IPCC, said in a 2014 report that for every degree Celsius of global warming, about 7 per cent of the world’s population will see a drop of at least 20 per cent in renewable water resources.



Scientists calculate the planet has already warmed one degree Celsius 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.



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