During the 1990s water, which is supporting life, was increasingly considered an economic as well as a social and environmental good. The water sector has significant economic weight and requires good governance. There is wide diversity among OECD member countries in terms of their water needs and available water resources. While most are industrialised countries, a minority are still in the process of development, with lower availability of water supply and sanitation. Water resources in eight member countries are already subject to high or medium-high stress; in a further eight water availability is becoming a constraint on development and significant investments are needed to marshal adequate supplies. Some other member countries, though relatively water-rich on a national scale, have extensive arid or semi-arid regions where the nature of development is necessarily shaped by water scarcity. A few countries have low population density and abundant water resources. In an international context, integration of upstream and downstream interests of transboundary water bodies is receiving increasing attention as these are a potential source of discord.