Last year was the driest year for the world's rivers in 33 years, says a new report coordinated by the World Meteorological Organization (WMO). According to the State of Global Water Resources Survey, the past five years have seen below-normal conditions for river flows and reservoir inflows worldwide. This increases the strain on global water supplies.
The annual report paints the big picture of the world's water cycle – from extreme floods to extreme droughts, from rivers and reservoirs to glaciers and groundwater. It brings together data from meteorological and hydrological services, data centers, members of the hydrological modeling community and supporting organizations such as NASA and the German Research Center for Geosciences.
"Water status is a major indicator of climate change. We are receiving distress signals in the form of increasingly extreme rainfall, floods and droughts that are wreaking havoc on ecosystems, economies and even taking lives. Melting ice and glaciers threaten long-term water security for many millions of people. And yet we are not taking the necessary urgent action," says WMO Secretary General Celeste Saulo.
What is happening to rivers around the world?
2023 showed mostly drier than normal river runoff – that is the volume of water flowing through a river at a given point in time. Over 50% of global catchment areas have recorded "abnormal conditions".
Drought and reduced river runoff have affected large parts of North, Central and South America, with the Mississippi showing record low water levels and the Amazon registering its lowest level ever. The Asian and oceanic Ganges, Brahmaputra, and Mekong river basins experienced below-normal conditions over nearly all of their territory.
But other rivers and reservoirs flooded with devastating impact: the east coast of Africa had excess water and flooding, as did the North Island of New Zealand and the Philippines.
In Europe, the UK, Ireland, Finland and parts of Sweden had above-normal discharge levels.
The climate crisis is leading to extreme changes in the global water cycle
Last year was the world's hottest year ever, with scientists agreeing that Earth's extreme temperatures are due to the climate crisis. The WCO report notes that the combination of prolonged droughts and devastating floods in 2023 can be attributed to both the climate crisis and the natural transition from La Niña to El Niño.
The climate crisis is making such natural weather events more extreme, scientists say, with impacts worsening and patterns becoming more chaotic, making them harder to predict.
Glaciers have seen their highest rate of water loss in 50 years
The State of Global Water Resources report looks at rivers along with reservoirs, lakes, soil, weather patterns and glaciers – which lost 600 gigatonnes of water last year.
Extreme melting patterns were seen in western North America and the European Alps, where Switzerland's glaciers lost about 10% of their volume in the past two years.
Northern Hemisphere snowpack declines in late spring and summer, the report noted, with last year's May snowpack the eighth lowest on record.