Climate change is going to increase water insecurity:

Many of the world’s most water-stressed areas will get less water, and water flows will become less predictable and more subject to extreme events. Among the projected outcomes:

• Marked reductions in water availability in East Africa, the Sahel and Southern Africa as rainfall declines and temperature rises, with large productivity losses in basic food staples. Projections for rainfed areas in East Africa point to potential productivity losses of up to 33% in maize and more than 20% for sorghum and 18% for millet.
• The disruption of food production systems exposing an additional 75–125 million people to the threat of hunger.
• Accelerated glacial melt, leading to medium term reductions in water availability across a large group of countries in East Asia, Latin America and South Asia.
• Disruptions to monsoon patterns in South Asia, with the potential for more rain but also fewer rainy days and more people affected by drought.
• Rising sea levels resulting in freshwater losses in river delta systems in countries such as Bangladesh, Egypt and Thailand.

Source: United Nations Human Development Report, 2006, p.15