Journal of Water Resources

Virtually all of these human uses require fresh water. Only
2.5% of water on the Earth is fresh water, and over two thirds
of this is frozen in glaciers and polar ice caps. Water demand
already exceeds supply in many parts of the world, and many
more areas are expected to experience this imbalance in the
near future. It is estimated that 70% of world-wide water use
is for irrigation in agriculture. Climate change will have
significant impacts on water resources around the world
because of the close connections between the climate and
hydrologic cycle.