A comprehensive assessment of fresh water resources has been prepared since Rio, at the request of the CSD (SEI, 1997).  Freshwater is clearly becoming a major constraint on development.  Forty percent of the world's population already face chronic water shortages (World Bank, 1995).  One recent estimate suggests that more than half of available freshwater resources are already being used to meet human needs, and this could rise to 70% in thirty years.  Water supplies could therefore run out in the next century if per capita consumption and excessive use in agriculture are not controlled (Postel et al., 1996).  Another projection shows that between 1 and 2.4 billion people will live in water-scarce countries by 2050 (WRI/UNEP/UNDP/WB, 1996).  The conflicts over sharing water in international river basins are increasing.

There are growing concerns about major regional water scarcities.  The Maghreb countries and Middle East already have 45 million people without adequate drinking water. Per capita water availability has shrunk by more than half in 30 years, and could be halved again in the next 30 years, requiring an investment of $50 billion (World Bank, 1996).  Three-fifths of Chinese cities are short of water and 80 million Chinese do not have adequate drinking water (Benjamin, 1994; Chen, 1995).

Water quality is gradually improving in most parts of Europe as a result of a massive investment programme.  However there still a problem with ground water and diffuse sources of pollution, particularly from agriculture  (EEA, 1995).