A century from now, the world will be a dryer place. Population rise will lead to a greater demand for water and climate change will decrease global rainfall, increase evaporation and lower supply. These changes will have a tangible impact on society, from individuals hoping to quench their thirst to governments planning national security strategies and international trade routes.
Northeastern University civil and environmental engineering associate professor Auroop Ganguly has developed a computational model to predict future water availability based on both climate– and global population change.
The findings — part of a larger research project funded by a five-year, $10 million National Science Foundation grant for understanding climate change with data-driven computational methods — were published in February in the journal Computers and Geosciences.
Today the world is home to nearly seven billion people, all vying for water from the same global pool. By the middle of the century, experts predict the population to increase to some nine or 10 billion. But moving forward, population predictions are less certain.
“From the middle of the century to the end of the century, that’s where there are multiple scenarios,” noted Ganguly, whose research focuses on climate change, water sustainability and extreme weather events such as hurricanes and heat waves.
In the “best-case” scenario, Ganguly said, the world will become more economically equitable. The income level of developing nations will begin to align with their more-developed neighbors.
“There’s almost a direct relation of income levels and lifestyles with population growth,” said Ganguly. “At the risk of over-generalization, if you are doing better economically, you tend to have less children, other things remaining the same.”
In the best-case storyline, global population growth slows down. But in the “worst-case” scenario, Ganguly added, the global economy will become less equitable and population growth will speed up.
“In a first order assumption about the change in the demand for water, one of the major factors is the change in population,” said Ganguly, who also heads Northeastern’s Sustainability & Data Sciences (SDS) Lab.
In the research paper, Ganguly and his colleagues Evan Kodra of the SDS Lab, Karsten Steinhaeuser of the University of Minnesota and Esther Parish of the Oak Ridge National Laboratory, presented a new computational and geographical information science (GIS) model to estimate per capita freshwater availability in 2025, 2050 and 2100. Computer-based predictions of greenhouse gas emissions over the next century drove the climate projections.
Regardless of the inputs, however, the GIS model projected less water availability in all three future decades. The surprising new finding is that population growth, not climate change, tends to have the larger impact on water availability both globally and across multiple regions of the world.
A related study of the continental United States by the same research team found that the worst-case climate change scenario would increase water stress in five percent of the population, but that a worst-case population growth scenario would increase water stress in 13 percent of the population.
The numbers seem striking, but Ganguly views these results as “exemplary insights” in need of more detailed analysis with a wider scope.