In short, barely 1% of the earth’s total water mass is available to meet human needs.

Water is however a renewable resource. The total volume of water on the globe is estimated at 1,400 million cubic kilometres (km3), a figure that remains fairly constant. Yet water circulates between land, oceans and the atmosphere, in what is known as the water cycle, with water being transformed from liquid to vapour and back again. Each year, approximately 577,000 km3 of water is recycled through this hydrological system.

Unequal distribution and increasing demand

Fresh water is distributed unequally around the planet, with tremendous disparities between populations and water resources: 9 countries share 60% of available resources.

Some countries – often emerging economies – experience water shortages made all the more serious by rapid population growth, which increases the need for drinking water but also for irrigation of crops intended for food (70% of available freshwater resources are used for agriculture alone). Currently, 25% of the world’s population lives in countries experiencing water stress, with annual fresh water resources of less than 1,700 m3 per capita (counting for just one quarter of the average volume available per capita worldwide).

While the quantity of water available on earth remains constant, demand has been increasing: over the next 20 years, needs will continue to rise along with population growth and industrial development. Already reduced by half over the past 50 years through this increased demand, the volume of fresh water available per capita risks dropping to 5,100 m3 by 2025, compared with 7,300 m3 today. Thus, disparities in water resource distribution are getting worse.

In parallel with these demographic and economic trends, pollution – whether urban, industrial or agricultural in origin – continues to have a sustained impact on the quantity and quality of fresh water.