By mid-century, water shortages could affect three billion more people than previously expected, and increased pollution will make river sources "dangerous" for people and wildlife, researchers have warned, AFP reports.
The United Nations climate science panel said about half the world's population is currently experiencing severe water shortages for at least one month a year, and warned that the impact of global warming and rising demand are the main risks to the world's supplies.
But a new study by scientists in Germany and the Netherlands has found that if harmful nitrogen pollution is taken into account, the number of areas experiencing water shortages is increasing dramatically.
"In general, people worry more about water scarcity - whether you have enough water," said lead author Mengru Wang of Wageningen University & Research.
"But I also see that water pollution is really becoming an increasingly important issue that makes water unsafe for use by nature and humans," he added.
Human activities dump large amounts of nitrogen, pathogens, chemicals and plastics into water systems.
Nitrogen, particularly from agricultural fertilizers, contributes to the growth of algae that can choke waterways, threaten marine life and degrade water quality.
The new study, published in the journal Nature Communications, analysed river basins around the world that are major sources of drinking water and centres of urban and economic activity.
According to the authors' computer modelling, the number of sub-basins - the smaller units within river basins - facing severe water shortages was twice as high as previously thought in 2010, and could worsen significantly in the coming decades.
They estimate that in 2010, 2,517 sub-basins in the world faced water shortages when the impact of nitrogen pollution on water quality was taken into account, compared to only 984 according to traditional quantity-based estimates.
That figure could rise to 3,061 by 2050, they found, estimating that this would affect an estimated 6.8-7.8 billion people - or about three billion more than in conventional estimates.
Co-author Benjamin Bodirsky, a senior research fellow at the Potsdam Institute for Climate Impact Research, said modelling three different scenarios that affect pollution levels shows that "we have choices and we can improve the situation".
But he said that even with the most optimistic estimates, nitrogen pollution would remain at "significant levels" in important agricultural regions such as Europe, China and India.
"The deterioration in access to water can be halted, and to some extent even reversed, by adopting more efficient use of fertilizers, as well as more vegetarian diets, and by connecting more of the world's population to water treatment facilities," Bodirsky said. / BGNES
