Climate change will affect the water security of developing countries. Freshwater is a scarce resource. Only 2.5 per cent of the 1.4 billion km3 of water on Earth is freshwater fit for human consumption, and most of this is inaccessible — nearly 70 per cent is locked up in glaciers, snow and ice. Our greatest source of freshwater is the 8 million km3 of groundwater, with only 0.3 per cent of freshwater (105,000 km3) being found in rivers, streams and lakes.Discussions about freshwater availability increasingly focus on water security, which refers to people's access to enough safe and affordable water to satisfy their needs for household use, food production and livelihoods.
Water insecurity can arise from physical scarcity, resulting either from climatic or geographical factors, or from unsustainable consumption or overexploitation. It can also have economic origins, with poor infrastructure or capacity preventing access to the water resources available, or occur where pollution or natural contamination renders water resources inaccessible.
Water insecurity and scarcity already affect large parts of the developing world. The past century has seen a sixfold increase in global water demand. Nearly three billion people (about 40 per cent of the global population) live in areas where demand outstrips supply.
This situation is set to worsen in the coming decades as populations grow, economies develop and agriculture a