The water stored on the world's land is steadily draining away, and 2025 was one of the driest years for the world's rivers in three and a half decades.
“The total volume of water stored on the continents is steadily decreasing,” said Robert Reinecke, professor of geography at Johannes Gutenberg University Mainz, who has helped compile the World Meteorological Organization's (WMO) State of Global Water Resources reports since the series began, in a statement released by the university on September 17, the day the 2025 edition was published.
Rivers carried less water in 36% of the world's basin areas in 2025 than in the 1991-2020 reference period, and the global total has been below that baseline every year since 2021. Groundwater is going the same way: levels were below the reference period at 65% of the monitoring stations the report covers, according to the Mainz statement, while the WMO's own summary says nearly two-thirds of monitored wells were outside their normal range, with the shift towards deficit rather than recovery. Glaciers lost around 408 gigatonnes of mass over the year, the fourth year in a row in which every glaciated region on Earth recorded a net loss, and roughly 1,400 gigatonnes over 2023-2025 combined.
Three depletion curves that used to be discussed separately are now moving together, which is what makes this report harder to dismiss as weather. Surface water, groundwater and ice are the buffers that absorb a bad year; all three thinning at once removes the margin that makes a drought survivable.
Reinecke attributes the trend to climate change and to human groundwater use. “A warmer atmosphere can hold more water; glaciers are melting, and at the same time, evaporation is increasing,” he said. “And we humans are transferring vast amounts of groundwater into the oceans and the atmosphere, for example, by using it for irrigation.” The water is not lost, he added, but is increasingly ending up in parts of the cycle where it is of less use to people and to many ecosystems.
The consequences are not evenly spread. Central Asia and Afghanistan are among the hardest-hit regions, with reservoir inflows across Tajikistan, Uzbekistan, Kyrgyzstan and Afghanistan markedly down, the Amu Darya and Syr Darya running below to much below normal, and more than half of river basin flow in the region derived from snow and ice that is itself disappearing. Central Asia was among the regions recording one of their three worst years for glacier mass balance on record.
What a thinning buffer looks like in practice was visible earlier this month in Nepal and Tibet, where a glacier collapse triggered floods that killed thousands of people, the university said, and last year in Africa, where heavy rains caused flooding that claimed numerous lives. The WMO says Asia and Africa are the regions most affected by water-related disasters, accounting for more than 80% of reported deaths over the past five years.
The report has been published annually since 2022 and has grown from three hydrological variables in its first edition to 15. This year's edition analysed water temperatures for the first time and found 2025 markedly warmer, a problem for both ecosystems and water quality. The WMO says global terrestrial water storage has been on a declining trend since 2014-2016.
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