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WATER POLITICS

Via Science, a report on a new study examining the Southern Hemisphere which has experienced a 20% drop in water availability in 20 years:

Water availability—the difference between precipitation and evaporation—is expected to decrease in many regions of the world because climate change has modified the water cycle, more water will be abstracted by the growing population, and water pollution will continue to limit clean water (1). Estimates of changes in water availability are uncertain at continental and global scales because measurements of precipitation and evaporation tend to be indirect or only locally representative (2). On page 579 of this issue, Zhang et al. (3) report a study that combines streamflow observations of large river basins of the world with terrestrial precipitation data and satellite measurements of evaporation and water storage to show that water availability in the Southern Hemisphere has substantially decreased from 2001 to 2020. With their approach, the authors have improved the reliability of water availability estimates, which could help improve long-term water management.