World’s water cycle ‘becoming more unpredictable’

GENEVA

(AFP Photo)

The planet’s water cycle is becoming increasingly erratic, swinging between too little and too much, the United Nations warned on Sept. 17, with an unprecedented El Nino expected to exacerbate the long-term trend.

Last year was among the driest for the world’s rivers in over three decades, the U.N.’s World Meteorological Organization (WMO) said in a report.

In 2025, one of the warmest years on record, glaciers also shrank across all regions, even as groundwater levels in many parts of the world are in multi-year decline, it found.

Overall, the WMO’s annual State of Global Water Resources report showed that the Earth’s freshwater storage, the total amount of water stored in groundwater, lakes and rivers, soil moisture, vegetation and ice and snow, continued a decade-long decline.

Some elements of the water cycle change rapidly, like precipitation, river flow and soil moisture, responding to weather within days or weeks.

WMO Secretary-General Celeste Saulo voiced particular concern about the decline in “slow reserves,” like groundwater and glaciers, which she said had traditionally served as the planet’s “savings account.”

They have served as “a buffer that absorbs bad years so that a single drought or a single dry season does not translate directly into a water crisis,” she told reporters.

Now, “we are depleting that savings account,” she warned. “We are spending our reserves.”

Glaciers have also been shrinking at a precipitous rate, with 2025 marking the fourth consecutive year where they shed significant ice mass across all regions.

Between 2023 and 2025, the report estimated that glaciers lost a cumulative global glacier mass of 1,400 giga tons of water, roughly equal to the water required to fill 560 million Olympic-sized swimming pools, or about a third of the world’s annual freshwater withdrawals.

“Groundwater tells a similar story: Nearly two-thirds of monitored wells worldwide showed conditions outside the historical norm in 2025,” Saulo said.

She highlighted that this was happening in parallel with “more water-related disasters.”

In particular, she pointed to the current El Nino pattern, which is expected to be the strongest since comparable records began four decades ago.

“The strengthening El Nino will increase the risk of drought in some areas, and flooding in others,” Saulo cautioned.

Already before El Nino hit, rivers worldwide were showing “abnormal” flows, WMO said, with 2025 among the three driest years for rivers in 35 years.

For a seventh year in a row, the number of river basins globally experiencing “normal” conditions were in a clear minority in 2025.

Only around 36 percent saw normal flows, while an equal percentage saw below-normal discharge conditions and 21 percent were above normal, the report found.