Mapping future water stress

These projections of per-capita water availability were made by Martina Floerke and colleagues at the University of Kassel in Germany.

They combined different types of forecast to obtain their results. A computer model of climate change developed by the UK Met Office Hadley Centre generates projections of how temperatures and rainfall are likely to change in the future.

The Kassel team applied Hadley projections on a finer geographical scale. These projections were fed into a program that models water flow in river basins.

The Intergovernmental Panel on Climate Change (IPCC) produces "scenarios" suggesting how society may develop economically and socially over time.

The Kassel researchers used these scenarios to project water use by various sectors of the economy. This particular analysis used the A2 scenario, where economic growth and technological change are "uneven", and population growth "high".

Having forecast the availability of water and the demand from industry, it was then possible to calculate how much water would be available per person at different points in the future.

These are projections, not predictions, and none of the models used are likely to be completely accurate in how they forecast the future.

The projections were adapted from a paper that originally appeared in the journal Hydrological Sciences in 2007.