Global warming and increased human population growth will affect future stresses on water resources. Vorosmarty et al. (2000) did a study predicting the effect of human economic and population growth and the effect of global warming consequences on the amount of water demand and water supply for 2025. They found that human population and economic growth will likely cause more water stress in future than the effects of global warming. However, climate change will likely interact with increasing demand to create more water stress than would otherwise happen .–Darien Martin
Voroosmarty, C., Green, P., Salisbury, J., Lammers, R., 2000 Global water resources:
vulnerability from climate change and population growth. Science 289, 284–288.
Vorosmarty et al. evaluated sustainable water supplies, defined as runoff from rivers, above ground or in shallow aquifers, in the time frame of 1985–2025. They considered how water supplies would be affected with climate change, and collected data to determine how these effects would interact with the effects of population fluctuations and industrial development. Water stress in regions around the world were characterized as the ratio of water taken from water bodies to amount of water discharged into streams. Domestic and industrial water stress were measured separately from agricultural water stress, and both factors are also shown combined.
They Vorosmarty et al. used this contemporary data to forecast water stress, climate change, increased human demand for water.
Today, one third of the human world lives with water stress, and about 7.9% live under severe water supply stress. Western North America, Central America, central, south South America, Central West coast of Africa, and Southern regions of Europe and Asia all have severe water stress.
The authors estimated that industrial and agricultural water needs, to 2025 are more affected by population and industry growth than by climate change. The population that was stressed both by population and industry growth and by climate change, was not substantially larger than the population impacted solely by population growth and industry growth alone.
Vorosmarty et al. also collected data on the Yellow and Chin Jiang rivers to demonstrate that, conditions vary greatly even between regions in close proximity. In a figure which shows water stress increasing as distance from the river increases, the Yellow River population is calculated to be less stressed with climate change impact, than the Chang Jiang River population is.
Climate change will limit water supplies in semi-arid and arid regions greatly, but population growth in cities and tropical climates is predicted to increase water stress more due to increased water pollution and demand.