Depending on diet and lifestyle
The world has abundant fresh water but it is unevenly distributed and under increasing pressure, United Nations agencies say, as highlighted by the drought in Cape Town.
On Tuesday South Africa declared the drought that has hit parts of the country and threatened to leave the Mother City without domestic tap water a national disaster.
More than 97% of the planet’s water is salty, most of it in the oceans and seas. But every year about 42.8-trillion cubic metres of renewable fresh water circulates as rain, surface water or groundwater, according to the UN’s Food and Agriculture Organisation (FAO).
This equals 16 216 litres a person a 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% of the planet’s fresh water reserve is locked up in the Antarctic ice cap.
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 UN said in 2015.
In the FAO’s most recent data (2014), it said 45 countries were experiencing water shortages, defined as less than one million litres a person a year. Twenty-nine were in a situation of extreme shortage, with less than 500 000 litres a person a year.
A third of the planet’s population depends on groundwater and the UN has warned of the danger of over-using these reserves. Groundwater reserves in part of India’s Ganges basin, southern Spain, Italy and California’s central valley could be drained dry within decades, it says.
Countries such as Canada, Russia and Peru use just 1% of their renewable fresh water. But others far overuse supply, such as Israel at 261% and Bahrain at 8.935%.
Countries that use more than their renewable supply of water draw from nonrenewable underground water or desalinated sea water, as in the case of Bahrain.
The global use of fresh water 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% by 2030.
“Water scarcity, exacerbated by climate change, could cost some regions up to 6% of their GDP, spur migration and spark conflict,” the World Bank said in 2016.
Farming is the biggest consumer of water globally (70%). Industry uses 19% and households 11%, according to the FAO.
But there are wide disparities at the regional level. In South Asia agriculture accounts for 91% of water use, against only 7% in homes and 2% in industry.
But in the European Union and North America industry consumes more than half the fresh water supply, ahead of agriculture (under 34%) and domestic use (under 18%).
The UN’s International Panel on Climate Change (IPCC), said in a 2014 report that, for every degree Celsius of global warming, about 7% of the world’s population will see a drop of at least 20% in renewable water resources.
Scientists calculate the planet has already warmed one degree Celsius since the Industrial Revolution kick-started 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 effect will depend on the level of warming. — AFP
The World Bank advises that data on water should be treated with caution given variations in national collection methods and seasonal and annual sampling