Continents Are Losing Water: WMO Report Reveals Rivers, Groundwater and Glaciers All in Decline

The planet’s freshwater stores are shrinking, and the latest assessment from the World Meteorological Organization leaves little room for doubt. The newly published “State of Global Water Resources 2025” report, released by the WMO on 17 September 2026, documents a steady decline in the total volume of water stored on the continents, a trend that scientists say is reshaping the global water cycle into something increasingly volatile and unbalanced. Professor Robert Reinecke of the Department of Geography at Johannes Gutenberg University Mainz, who has been a central contributor to the annual report since its inception in 2022, summarizes the situation bluntly: the reservoir of water held on land is steadily decreasing, and the consequences are already visible in rivers, aquifers and glaciers around the world.

The evidence in the rivers is among the starkest findings. Since 2021, the total volume of water flowing through the world’s rivers has consistently been lower than the average recorded during the reference period from 1991 to 2020. The most recent year ranks among the driest of the past three and a half decades. In 2025, rivers carried less water than the comparison baseline in 36 percent of the world’s basin areas, meaning that more than a third of the planet’s drainage regions experienced below-normal river flows. This sustained deficit is not a single-year anomaly but a multi-year pattern, suggesting a structural shift in how water is distributed across the terrestrial branch of the hydrological cycle.

Below the surface, the picture is equally troubling. Groundwater levels in 2025 were lower than the reference-period values at 65 percent of all monitoring stations included in the analysis. Because groundwater supplies drinking water for billions of people and sustains irrigation agriculture across vast agricultural regions, a widespread decline in aquifer levels carries implications far beyond hydrology. It touches food security, energy production, ecosystem health and the political stability of water-stressed regions. The report’s methodology for analyzing groundwater data was developed in part by Reinecke’s research group at JGU, working alongside researchers from Goethe University Frankfurt am Main and the Global Runoff Data Center in Koblenz, which operates under the auspices of the WMO.

The third major indicator, the world’s glaciers, continues its dramatic retreat. Last year, glaciers lost approximately 400 gigatons of mass, an almost incomprehensible quantity when translated into everyday terms. A single gigaton is one billion tons of water, so 400 gigatons represents an enormous transfer of frozen freshwater into the liquid water cycle and, ultimately, the oceans. The dangers of this destabilization became tragically clear just weeks before the report’s publication, when a glacier collapse triggered a devastating flood disaster in Nepal and Tibet that claimed thousands of lives. Glacial lake outburst floods of this kind are an increasing hazard in high-mountain Asia as warming temperatures melt ice and destabilize slopes.

The report’s authors attribute the continental drying to two interacting drivers: climate change and human consumption of groundwater. As Reinecke explains, a warmer atmosphere can hold more water, which intensifies both evaporation and the extremes that result when that moisture is suddenly released. Glaciers are melting, shifting the timing and volume of meltwater flows that billions of people downstream depend on. At the same time, humanity is extracting vast quantities of groundwater and effectively transferring it into the oceans and the atmosphere, for example by pumping it onto fields for irrigation. Much of that irrigated water evaporates or runs off, eventually reaching the sea rather than recharging the aquifers from which it was drawn.

The combination of these forces is drying out the continents in a precise physical sense. The water itself is not destroyed or lost from the planet; the Earth’s total water budget remains essentially fixed. What is changing is its distribution. Water is increasingly found in parts of the cycle where it is of little use to humanity and many ecosystems, locked in the atmosphere as vapor, sitting in the ocean as saltwater, or displaced from seasonal snowpack and soil moisture into flood pulses that arrive and disappear within days. The practical result is a widening gap between when and where water is available and when and where it is needed, manifesting simultaneously as extreme droughts in some regions and catastrophic floods in others.

The geography of these extremes in 2025 was global. In Africa, heavy rains led to flooding that claimed numerous lives during the same period in which river basins across other continents ran dry. This simultaneity of surplus and scarcity is a hallmark of an intensified hydrological cycle: warmer air moves more water, and it moves it less gently. For water managers, the challenge is no longer simply average availability but the growing volatility of supply, which overwhelms infrastructure designed for the more stable conditions of the twentieth century.

The 2025 edition of the report is also the most comprehensive the WMO has produced. Among the new elements is the first analysis of water temperature data. According to the findings, 2025 was characterized by significantly higher water temperatures in rivers and other surface waters. Warmer water holds less dissolved oxygen, stresses aquatic species, and accelerates the growth of harmful algal blooms, so rising water temperatures pose problems for both ecosystems and water quality. For drinking-water treatment plants, warmer raw water can also mean higher processing costs and greater vulnerability to contamination events, adding a further layer of concern for utilities already strained by fluctuating flows.

Behind the headline numbers lies a substantial scientific and technical effort. Reinecke and his colleagues contributed model results and data to the report from JGU, Goethe University Frankfurt and the Global Runoff Data Center in Koblenz. The Mainz group helped develop the methodology for analyzing groundwater data and played a leading role in further developing one of the global water models used in the assessment. These models are innovative in that they simulate groundwater explicitly, rather than treating it as a static reservoir, allowing researchers to track how climate change propagates through soil moisture, river discharge and aquifer storage simultaneously. That capability is essential for producing an integrated picture of continental water storage rather than a patchwork of disconnected observations.

The trajectory the report describes raises difficult questions for the coming decades. If river flows remain below the 1991 to 2020 baseline year after year, groundwater levels continue to fall across most monitoring stations, and glaciers keep shedding hundreds of gigatons of mass annually, the communities that depend on these sources will face progressively harder choices about allocation, conservation and adaptation. The report’s core message is that the water crisis is no longer a distant scenario but an observable, measurable present, documented with increasing precision by an international scientific collaboration. Reversing the continental drying trend would require addressing both the climatic drivers that intensify the water cycle and the extraction practices that deplete subsurface reserves, a dual challenge that spans energy policy, agriculture, and international cooperation on a scale the report makes abundantly clear the world has yet to meet.

Subject of Research: Global water resources decline in rivers, groundwater and glaciers documented by the WMO State of Global Water Resources 2025 report

Article Title: WMO report on global water resources: worldwide continents are drying up

Article References: WMO report on global water resources: worldwide continents are drying up. (n.d.). Original publication

Image Credits: AI Generated

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Keywords: WMO, global water resources, groundwater decline, river discharge, glacier mass loss, climate change, hydrology, water cycle, drought, flooding, water temperature, JGU Mainz