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published on 18 May 2018 in water

Aerial views of the state of water resources

NASA has recently published a survey in the scientific journal Nature on the state of fresh water reserves on our planet; it reveals that the wet areas of the Earth are becoming increasingly wetter, while the dry areas are becoming progressively drier. This phenomenon is caused by various factors, including the not very sustainable management of water resources, climate changes and natural cycles (for example, alternation of wet and dry periods associated with El Niño and La Niña). Thanks to this survey, researchers are now able to understand where, how and why the water resources of our planet are changing.
To complete this survey, the research team used the data collected by the NASA GRACE (Gravity Recovery and Climate Experiment) satellite mission in 14 years of observation, from 2002 to 2016. The survey succeeded in mapping water resources all over the planet, monitoring and collecting data even on previously little-known areas or those for which there was not sufficient documentation.

Time series showing global freshwater trends on Earth from 2002 to 2016. Above average increases in freshwater are shown in blue, while those lower than average are in red. Credit: NASA’s Scientific Visualization Studio

The red areas, indicating freshwater reserves that are diminishing, are those that arouse most concern. More specifically, 19 points where water resources are dramatically depleting have been identified, including northern and eastern India, the Middle East, California and Australia, where excessive use of water resources have caused a serious decline in the availability of freshwater. A sharp drop in water resources has been observed in Xinjiang province too, in North-West China, even though precipitations were normal in the region. In this case, depletion of ground water is caused by industry and irrigation, which draw off more water than is replaced by rainfall and percolation. Over the past thirty years, Turkey has built no less than 22 dams along the Tigris and Euphrates Rivers. This has considerably impoverished water resources, which are now almost a third lower than normal, making the area the largest hotspot showing a deficit identified by the survey.
The authors of the research deem that it is still too early to state that these changes are the result of global warming. Nevertheless, they stress that there is a “clear human impact” on the global water cycle.

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