Why are humans so enthusiastic about discovering traces of water on Mars, and yet do not treat the Earth's supply of "blue gold" with the same respect nor seek to share it more fairly?
So asks the World Water Development Report 2021, which argues that many people waste or misuse water because they tend to think only of what it costs in monetary terms.
That underestimates its real worth, which also includes harder-to-measure cultural or health benefits - for example, how a clean water source near home allows girls to go to school.
"Many of our problems arise because we do not value water highly enough; all too often water is not valued at all," said Gilbert F. Houngbo, chair of UN-Water, in a statement to mark the report's release on World Water Day, observed each year on 22 March.
Here are 10 facts about water and how vulnerable communities are struggling to access supplies as growing demand and a warming planet raise the risk of shortages:
- Four in 10 people worldwide do not have enough safe drinking water. By 2050, more than half of the global population is expected to face water stress, which arises when demand outstrips available water resources.
- More than 2 billion people live in countries experiencing water stress, and an estimated 4 billion people live in areas that suffer from severe water scarcity for at least one month per year.
- One in five children worldwide do not have enough water to meet their daily needs, and children in more than 80 countries live in areas with high water vulnerability, meaning they depend on surface water, unimproved sources or water that takes more than 30 minutes to collect.
- Eastern and southern Africa have the highest proportion of children living in such areas, with 58% facing difficulty accessing sufficient water every day.
- Two in five people worldwide, or 3 billion, do not have a hand-washing facility with water and soap at home, including nearly three-quarters of people in the poorest countries.
A file photo shows a Palestinian boy drinking water from a tap in the town of Khan Yunis in southern Gaza Strip. Providing access to safe drinking water and sanitation in 140 low and middle-income countries would cost $114 billion per year.
- Providing access to safe drinking water and sanitation in 140 low and middle-income countries would cost $114 billion per year, whereas the many social and economic benefits of safe water are hard to evaluate.
- Global freshwater use has increased six-fold over the past 100 years and continues to grow at a rate of about 1% per year since the 1980s.
- Agriculture accounts for nearly 70% of global water withdrawals, mainly for irrigation but also for livestock and aquaculture. The ratio can reach up to 95% in some developing countries.
- Climate change is altering rainfall patterns, reducing water availability, and worsening the damage caused by floods and drought around the world.
- The melting of ice cover and glaciers – known as the water towers of the world - is leading to more hazards such as flash floods in the short-term, while threatening to reduce water supplies for hundreds of millions of people in the future.
Sources: UN World Water Development Report 2021, World Meteorological Organization, UNICEF (Reporting by Megan Rowling; Editing by Helen Popper for the Thomson Reuters Foundation