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.

Visit IRis, Northeastern’s archive of dig­ital schol­ar­ship, pub­lishing and preser­va­tion for work by Auroop Gan­guly.