Worldwide, over 2 billion people live in areas of water stress and 500 million people live in a state of chronic water shortage.
It is estimated that, by 2025, 50% of the world's population will face water shortages.
Global warming will lead to:
Changes in climate patterns, so rain-bearing winds will reach some areas less regularly.
An increase in the rate of glacier melting.
More extreme weather events, with floods and storms as well as droughts.
The global effects of population growth and climate change combined could be devastating in terms of water scarcity.
Richer countries can afford to buy their way out of water stress - for example, Kuwait and Saudi Arabia can afford to build DESALINATION plants to convert salt water from the sea into drinking water. They can do this because of the profits they get from their oil industries.
Rapid changes in weather patterns could spell disaster for poor subsistence farmers in developing countries, who rely on rain to water their crops.
These farmers are increasingly vulnerable to unstable weather patterns and, for them, water insecurity will almost certainly lead to food insecurity.
The Sahel is a belt of semi-arid land immediately south of the Sahara desert. Rain falls in only 1 or 2 months of the year, and both the total amount of rainfall and the length of the rainy season are very variable.
Sometimes the rain comes in torrential downpours and is then lost as surface runoff, causing flooding. In other years the rains fail completely leading to lengthy droughts.
Drought causes seasonal rivers and water holes to dry up and the water table to fall.
Drought spells disaster for the nomads who graze animals, and for subsistence farmers who rely on rain to grow maize.
Grasses die, and soil erosion & desertification follow, due to overgrazing by animals.
Water isn't just for drinking and washing. It's used for industry, farming, power generation and for waste disposal. We also use it for recreation (fishing, surfing, sailing etc.)
The wide range of uses reflects the processes and links within the water cycle and humans do interfere in this process.
For example, we may cut down trees (deforestation) which could lead to more flooding, we build large dams and reservoirs, we build towns and cities which reduces evapotranspiration and we overabstract water (take too much).
Many of the countries in the Sahel are developing countries (eg Chad, Sudan) and are among the poorest in the world. Their rapidly growing populations puts pressure on food supplies in drought years.
Some solutions are suggested in the video.