Urban population growth and climate change could result in chronic water shortages for nearly 1 billion people in developing nations, according to a study published in the March 28, 2011 Early Edition of Proceedings of the National Academy of Sciences of the United States of America.

The study’s authors used demographic and geographic data to project changes in water availability for cities in developing countries with at least 100,000 people. Their analysis suggests that population growth alone will result in year-round water shortages for 993 million city-dwellers by 2050 — up from 150 million in 2000. An additional 100 million city-dwellers could face year-round water shortages by 2050 due to changes in rainfall patterns.

Year-round water shortages will hit the Middle East and North Africa the hardest, according to the scientists. Seasonal water shortages, however, will occur on every continent and across many climates by 2050. About 3 billion people in cities may have insufficient water for at least one month of the year, due to both population growth and climate change.

The authors stress that these are early projections. But their estimates of water availability actually may be conservative, because they assume that all the available water is clean enough to use. Their models also did not fully account for climate-driven changes in glaciers and snow packs, which are important sources of water for many regions.

You can download the paper here.