The water cycle you learned about in school is off balance. The consequences affect everyone on Earth

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The water cycle you were taught in school is being thrown off balance by fossil fuel pollution, bringing a host of dangerous consequences including shrinking rivers, disappearing glaciers and wild swings between floods and drought , according to the World Meteorological Organization’s annual analysis of global freshwater.

The water cycle refers to the complex system by which water moves around the Earth. It evaporates from the ground — including from lakes and rivers — and rises into the atmosphere, forming large streams of water vapor able to travel long distances, before eventually falling back down to Earth as rain or snow.

This cycle is becoming “more erratic and unpredictable,” warns the WMO’s State of Global Water Resources Report published Thursday, which covers 2025, one of the planet’s warmest years on record.

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The total amount of freshwater stored in the Earth’s rivers, lakes, aquifers, ice, snow and soils is in decline, the report found using satellite data. In 2025, 42% 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.

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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.

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 the historical norms last year, with the balance shifting further toward deficit compared to 2024.

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.

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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.”

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.

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In the US, catastrophic f looding 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.

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 “the integrity of the global water cycle is at stake — we need to act now.”

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根据世界气象组织对全球淡水的年度分析，你在学校里学到的水循环正因化石燃料污染而失去平衡，带来一系列危险的后果，包括河流萎缩、冰川消失以及洪水和干旱之间的剧烈波动。

水循环是指水在地球上循环的复杂系统。水从地表（包括湖泊和河流）蒸发，上升到大气层，形成能够远距离移动的大股水汽流，最终以降雨或降雪的形式落回地球。

世界气象组织周四发布的《全球水资源状况报告》警告说，这一周期正变得“更加不稳定和不可预测”。该报告涵盖了 2025 年，这是地球有记录以来最温暖的年份之一。

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该报告利用卫星数据发现，地球河流、湖泊、含水层、冰雪和土壤中的淡水总量正在减少。到2025年，全球42%地区的淡水储量将低于历史平均水平。

世界气象组织水文和冰冻圈主任韦恩·詹金森表示：“方向很明确：自 2016 年左右以来，全球陆地储水量一直在下降。”

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去年是全球河流近 35 年来最干旱的一年，受影响的地区包括北美大部分地区、南美部分地区、东欧、中东和中亚。

河流是重要的贸易动脉，是人们、农场和工业的水源，是电力生产商的来源，是野生动物的栖息地，也是旅游景点。

全球已连续七年河流流量异常。报告指出，虽然部分河流在2025年的流量高于平均水平——包括南亚、东南亚和澳大利亚的部分地区——但绝大多数河流的流量低于平均水平。

全球地下水的情况也类似。去年，三分之二的监测井水位超出历史正常水平，而且与2024年相比，缺水情况将进一步加剧。

全球冰冻地区也出现了令人担忧的变化。2025年，所有地区的冰川都出现了大范围消融，这已是连续第四年发生这种情况。报告估算，2023年至2025年间，冰川消融的水量足以填满约5.6亿个奥运会标准游泳池。

冰川融化会带来洪水和海平面上升等灾害，还会给依赖冰川的20亿人带来用水安全风险。

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与河流和湖泊等快速流动的部分相比，冰川、积雪和冰构成了水循环中较慢的部分，它们的积累和消退需要更长的时间。

世界气象组织秘书长塞莱斯特·萨乌洛表示：“传统上，这些缓慢释放的水资源储备就像地球的储蓄账户：一个缓冲地带，可以吸收干旱年份的影响，使一次干旱或一个旱季不会直接演变成水危机。我们正在耗尽这个储蓄账户。”

随着水循环的变化，极端天气事件也日益增多。报告指出，过去五年都出现了破纪录的洪水和干旱，一些地区甚至来不及从一次极端事件中恢复过来。

就灾害事件数量和人员伤亡而言，亚洲和非洲是受影响最严重的地区。尼日利亚和刚果民主共和国等国遭遇了严重的洪灾，南亚和东南亚部分地区去年也遭受了热带气旋和强季风降雨的袭击。

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2025 年 7 月，美国德克萨斯州丘陵地带发生灾难性洪水，造成 130 多人死亡；2025 年 7 月，飓风梅丽莎席卷加勒比海地区，包括牙买加和海地在内的多个岛屿，造成 90 多人死亡。

另一方面，东欧、地中海和中东部分地区遭受了严重的干旱。

报告警告称，今年极端天气事件可能会更加频繁。“厄尔尼诺现象的增强将增加一些地区发生干旱的风险，而另一些地区则可能面临洪涝灾害，”萨乌洛说。

该报告引用了来自60多个国家的水资源信息，但作者指出，仍然存在关键的数据缺口，尤其是在极端天气事件最为严重的地区，例如亚洲和非洲。詹金森表示，弥补这些缺口至关重要，因为“我们无法管理我们没有测量的东西”。

澳大利亚科廷大学地下研究和地下水生态小组的联合负责人马蒂亚·萨科（Mattia Saccò）并未参与该报告的撰写，但他表示，该报告“突显了全球水循环所有主要组成部分令人担忧的下降趋势”。

“水资源——我们星球的生命之源——的质量和数量急剧下降，其后果包括生物多样性丧失、生态系统减弱，以及整个世界变得更加脆弱，”他说道，“全球水循环的完整性正受到威胁——我们现在必须采取行动。”