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Tool investigates population, climate impacts on global water resources


A method combining geographic information systems data with climate models and statistical analysis is provid­ing insight into the relative impact of population growth and climate on global freshwater supplies.

“Our tool provides a simple method to integrate disparate climate and popu­lation data sources and develop prelimi­nary per capita water availability projec­tions at a global scale,” said Esther Parish of the Oak Ridge National Laboratory (ORNL) Environmental Sciences Division.

When Parish and co-authors Auroop Ganguly, Karsten Steinhaeuser, and Evan Kodra began working on this approach in 2009, it was unusual to integrate population, climate, and water data in one model. The toolkit they developed, which is freely available, may be devel­oped further for more complex analyses.

The study considered water stress to be less than 450,000 gallons avail­able per person per year. However, how a society stores and allocates wa­ter—for example, among residential, agricultural, and industrial uses—will determine whether an actual shortage exits.

The team used ORNL’s Global LandScan population distribution da­taset in combination with population growth projections from the Intergov­ernmental Panel on Climate Change to estimate freshwater demand by 2025, 2050, and 2100. They used the Community Climate System Model 3 to estimate water availability during the same periods and then combined supply and demand projections to estimate water availability worldwide.

To test the tool, they plugged in four IPCC greenhouse emissions projec­tions and global population projections to arrive at potential scenarios. None of the scenarios looks good: the results suggest 56 to 75% of the world’s popu­lation, including residents across much of the United States, might experience freshwater stress by 2100. The study offers preliminary in­sights, but future research needs to in­corporate output from multiple climate models, Parish noted.

Ganguly and Kodra, both of North­eastern University, and Steinhaeuser, Univer­sity of Minnesota, are former ORNL staff. The work was funded by ORNL’s Labora­tory Directed Research and Develop­ment program and the National Science Foundation.

Reference: Parish, et al. 2012. “Estimating future global per capita water availability based on changes in climate and population,” Computers & Geosciences, 42, 79-86.

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