Desalination plants are large-scale installations which remove the salt from sea water, making it suitable for human use. The number of desalination plants is increasing throughout the world, but the process is both expensive and energy intensive. If the power required is generated by burning fossil fuels, the resulting carbon dioxide emissions contribute further to climate change. However, in countries such as Spain, where the Sun’s energy is in plentiful supply, it can be a viable option. Spain already has 700 desalination plants – a number which is expected to double by 2050. But in more temperate regions where solar energy is not a sufficient power source, desalination may not be the best choice.

Recycling waste water from bathrooms and washing machines can leave more tap water available for drinking and washing. For example, in the Australian town of Rouse Hill nearly 20,000 homes recycle water, reducing the demand for tap water by 40%. In some places periods of drought mean that short-term methods of accessing more water are already necessary. Chile is one of several countries that now have ‘water markets’ in which regions trade water to meet their demands.

As well as adapting the water supply itself, pressures on water resources can be alleviated by reducing the demand for water. Such measures may help communities in areas of existing water stress to respond to the possible impacts of a warming world. One-sixth of the world’s population currently live in areas regularly subject to water shortages, and this figure could increase as a result of climate change. Water metering, combined with water-efficient appliances, can reduce water usage. On average, people with water meters use about 10–15% less water than those without.

• World Meteorological Organisation: Water
• Koshland Science Museum: Online Activity