Decadal decline in terrestrial storage

The World Meteorological Organization published its annual global water resources assessment on 17 September 2026, evaluating five years of observations through the end of 2025. The findings show that terrestrial water storage, which includes groundwater, lakes, rivers, soil moisture, vegetation, snow, and ice, has shrunk continuously since the mid-2010s. Global freshwater cycles have grown increasingly erratic, swinging between localized droughts and sudden inundations instead of maintaining predictable distributions. WMO Secretary-General Celeste Saulo compared natural slow-response storage systems to a financial cushion that traditionally protected communities during lean periods.

“These reserves have buffered bad years so that a single drought or a single dry season does not immediately lead to a water crisis.”

Saulo warned that humanity is now actively depleting this natural savings account.

River discharge and groundwater deficits

Global river basins experienced one of their three driest periods in 35 years during 2025. Water discharge fell below normal levels across approximately 36% of global catchment areas. Only 34% to 38% of river basins registered normal water volumes, dropping significantly from the 46% baseline average observed between 1991 and 2020. The past seven years collectively registered fewer rivers with normal flow rates than any comparable span since 1991.

Groundwater levels exhibited similar stress across monitored regions in 2025. Nearly two-thirds of monitored wells worldwide recorded water levels outside their historical norms. Central and Eastern Europe experienced severe deficits relative to the 2014 to 2024 reference period, while groundwater in most of Northern Europe remained above long-term averages.

Glacier retreat and compound climate drivers

Glacier retreat continued across all monitored glacial regions for the fourth consecutive year in 2025. Earth lost a total of 1,400 gigatonnes of glacial water mass between 2023 and 2025. This volume equals roughly 560 million Olympic swimming pools, representing approximately one-third of annual global freshwater withdrawals. Wayne Jenkinson, director of the WMO Hydrology and Cryosphere branch, stated that human-induced climate change, increasing water consumption from a growing global population, and natural variability all contribute to the declining reserves.

Vulnerable regions and El Niño risks

Water extremes have disproportionately impacted developing regions over the past five years. At least half of all recorded water-related extreme events occurred in Asia and Africa, and more than 80% of related fatalities were concentrated on those two continents. The WMO noted that its assessment concluded with 2025 data, excluding the river lows recorded on European waterways such as the Rhine and Danube during the summer of 2026. The organization warned that the developing El Niño weather pattern will alter global atmospheric cycles, elevating flood risks in some regions while intensifying droughts in others.