Climate change that warms the atmosphere and oceans will change major weather systems, with greater likelihood of extremes – droughts and floods – in different parts of the world.
These changes will, in turn, affect human livelihoods, particularly those dependent on direct access to natural assets. Rain-fed agriculture, human settlement patterns and movement, water supplies, sanitation and irrigation will all be affected, leading to changes in human health, wealth and security. On the demand side, as populations grow and move – and as their income levels increase or decrease – their demand for water resources will change.

Taken together, these changes will present major challenges to future management of water resources for human and ecosystem development.

This Background Paper, one of four prepared for World Water Day 2009, calls for more sensitive analysis, combined with stronger scenario planning that takes as its starting point the development needs of populations. What will demand be, and why, in time and space across different sectors, and what are the likely ‘bads’ to avoid and ‘goods’ to support?