Remember the water cycle diagram from school? The one with evaporation, condensation, and precipitation in a neat, balanced loop? That balance is gone. Fossil fuel pollution has thrown the planet's most fundamental system into chaos, and the consequences are showing up in shrinking rivers, vanishing glaciers, and violent swings between flood and drought, according to the World Meteorological Organisation's (WMO) annual analysis of global freshwater.
The water cycle is the complex system by which water moves around the Earth. It evaporates from lakes, rivers, and the ground, rises into the atmosphere as vapor, travels vast distances, and falls back down as rain or snow. It is becoming more erratic and unpredictable, warns the WMO's State of Global Water Resources Report, released Thursday and covering 2025, one of the planet's warmest years on record.
Why is the global water cycle becoming more erratic?
The total amount of freshwater stored in rivers, lakes, aquifers, ice, snow, and soils is in decline, the report found using satellite data. In 2025, 42 percent of the world had storage levels below historical norms. The direction is clear: water stored on land has been declining globally since around 2016, said Wayne Jenkinson, the WMO's director of hydrology and cryosphere.
Last year was one of the driest for the globe's rivers in the past 35 years, with affected areas including much of North America, parts of South America, Eastern Europe, the Middle East, and Central Asia. Rivers are vital trade arteries, sources of water for people, farms, and industry, electricity producers, wildlife habitats, and tourist draws.
What does the data say about rivers and groundwater?
The planet has now experienced seven years of abnormal river flows. While some rivers saw above-average flows in 2025, including in parts of South and South East Asia and Australia, a greater percentage were below average, according to the report. It's a similar story for the world's groundwater. Two-thirds of monitored wells experienced conditions outside historical norms last year, with the balance shifting further toward deficit compared to 2024.
How are glaciers and frozen regions being affected?
The world's frozen regions also experienced concerning shifts. All regions experienced widespread glacier loss in 2025, for the fourth year straight. Between 2023 and 2025, glaciers lost enough water to fill about 560 million Olympic-sized swimming pools, the report calculated. Melting glaciers bring hazards like floods and rising sea levels, as well as the risk of water insecurity for the two billion people who rely on them.
Glaciers, snow, and ice form the slow part of the water cycle, as compared to faster parts like rivers and lakes, accumulating and depleting over longer periods. Traditionally these slow reserves have acted as the planet's savings account: a buffer that absorbs bad years so that a single drought or a single dry season does not translate directly into a water crisis, said WMO Secretary-General Celeste Saulo. We are depleting that savings account.
How is extreme weather linked to the water cycle?
As the water cycle shifts, the weather is becoming more extreme. The past five years have all seen record-breaking floods and droughts, with some places having little time to recover between one extreme event and the next, the report found. Asia and Africa were the most affected regions, in terms of number of events and lives lost. Countries including Nigeria and the Democratic Republic of Congo experienced major flooding, and parts of South and Southeast Asia were hit by tropical cyclones and intense monsoon rains last year.
In the US, catastrophic flooding in the Texas Hill Country in July 2025 killed more than 130 people, and in the Caribbean, Hurricane Melissa tore across islands including Jamaica and Haiti, killing more than 90 people. At the opposite end of the spectrum, parts of Eastern Europe, the Mediterranean, and the Middle East endured severe drought. This year could see even more extremes, the report warned. The strengthening El Niño will increase the risk of drought in some areas, and flooding in others, Saulo said.
What are the gaps in our understanding of the water cycle?
The report drew on water information from more than 60 countries, but the authors note that there are still critical data gaps, often from regions where extremes are most severe, including Asia and Africa. It's critical to close these gaps as we cannot manage what we do not measure, Jenkinson said.
Mattia Saccò, co-leader of the Subterranean Research and Groundwater Ecology Group at Curtin University in Australia, who was not involved in the report, said it highlights alarming declining trends across all major components of the global water cycle. The implications of this plunge in the quality and quantity of water, the lifeblood of our planet, involve loss of biodiversity, weaker ecosystems and, overall, a more fragile world, he said, adding that the integrity of the global water cycle is at stake and we need to act now.
What does this mean for Aotearoa New Zealand?
For a country that prides itself on clean, green rivers and alpine glaciers, this report is a stark reminder that no one is immune. Our own glaciers have been in retreat for decades, and our regions are no strangers to the whiplash of drought and deluge. The data from the WMO makes it clear: the slow reserves we have relied on are being drawn down, and the fast parts of the cycle are becoming less predictable. As a nation that depends on agriculture, hydropower, and tourism, the stakes could not be higher. The question is not whether we adapt, but how quickly we can shift our own relationship with water before the savings account runs dry.