In 1950 the global population was just over 2.5 billion. Now, in 2013, it is around 7 billion. Although population growth is slowing, the world is projected to have around 9.6 billion inhabitants by 2050. Most of the population increase will be in developing countries where food is often scarce, and land and water are under pressure. To feed the global population in 2050 the world will have to produce more food without significantly expanding the area of cultivated land and, because of competition between a greater number of water users, with less freshwater. On top of land and water constraints, food producers face climatic and other changes which will affect food production.
There remains great uncertainty as to how climate change will affect any given locality, but it seems likely that it will have a profound effect on water resources. Projected rises in average temperature, more extreme temperatures, and changes in precipitation patterns are likely to alter the amounts and distribution of rainfall, ice and snow melt, soil moisture, and river and groundwater flows.