The year 2023 marked the driest year for global rivers in more than three decades, according to a new report coordinated by the World Meteorological Organization (WMO), which signaled critical changes in water availability in an era of growing demand.

Released on Monday, the report shows that the last five consecutive years have seen widespread conditions of below-normal river flows, with reservoir flows following a similar pattern. This situation reduces the amount of water available for communities, agriculture and ecosystems, which puts the world's water supply even more at risk, says the WMO, in a publication on the WMO's website. Negócios newspaper.

Glaciers have suffered the greatest loss of mass ever recorded in the last five decades, with 2023 being the second year in a row in which all regions of the world with glaciers have lost ice.

2023 was also the hottest year on record, with high temperatures and widespread dry conditions contributing to prolonged droughts. But there was also a significant number of floods around the world. Extreme hydrological phenomena were influenced by natural climatic conditions - the transition from La Niña to El Niño in mid-2023 - as well as human-induced climate change.

"We are receiving distress signals in the form of increasingly extreme precipitation, floods and droughts, which are severely affecting lives, ecosystems and economies. Melting ice and glaciers threaten long-term water security for many millions of people. And yet we are not taking the urgent action needed," says WMO Secretary General Celeste Saulo.

"As a result of rising temperatures, the hydrological cycle has accelerated. It has also become more erratic and unpredictable, and we are facing increasing problems of excess or lack of water. A warmer atmosphere retains more moisture, which favors heavy rainfall. Faster evaporation and drying out of the soil exacerbate drought conditions," he adds.

The State of the World's Water Resources report series provides a comprehensive overview of the world's water resources. It is based on contributions from dozens of National Meteorological and Hydrological Services and other organizations and experts. It seeks to inform decision-makers in water-sensitive sectors and disaster risk reduction professionals.

"Very little is known about the true state of the world's freshwater resources. We can't manage what we don't measure. This report seeks to help improve monitoring, data sharing, transboundary collaboration and assessments," says Celeste Saulo. "This is urgently needed."

According to the WMO, the State of Global Water Resources report is the most comprehensive to date, with new information on lake and reservoir volumes, data on soil moisture and more details on glaciers and snow water equivalent.

The year 2023 was marked by river discharge conditions that were mostly drier than normal, compared to the historical period. As in 2022 and 2021, more than 50% of the global river basins showed abnormal conditions, most of them in deficit. A smaller number of basins recorded above-normal conditions.

Large swathes of North, Central and South America suffered severe droughts and reduced river discharge conditions in 2023. The Mississippi and Amazon basins recorded low water levels. In Asia and Oceania, the large basins of the Ganges, Brahmaputra and Mekong rivers recorded below-normal conditions throughout most of the basin.

The east coast of Africa recorded above and well above normal discharge and flooding. The North Island of New Zealand and the Philippines recorded annual discharge conditions well above normal. In northern Europe, the whole of the United Kingdom and Ireland recorded above-normal discharges, as well as Finland and southern Sweden.

Glaciers have lost more than 600 gigatonnes of water, the worst in 50 years of observations, according to preliminary data for September 2022 - August 2023. This "severe loss" is mainly due to extreme melting in western North America and the European Alps, where Switzerland's glaciers have lost around 10% of their remaining volume in the last two years.

The report points out that snow cover in the northern hemisphere has been decreasing in late spring and summer: in May 2023, the extent of snow cover was the eighth lowest on record (1967-2023). In North America, May's snow cover was the lowest in the same period.

Summer ice mass loss over the past few years has indicated that glaciers in Europe, Scandinavia, the Caucasus, northern Western Canada, southern Western Asia and New Zealand have passed peak water (maximum melting rate of a retreating glacier; leading to reduced water storage and availability afterwards), while the Southern Andes, the Russian Arctic and Svalbard still appear to be showing increasing melting rates.

The report also warns that 3.6 billion people do not have adequate access to water for at least one month a year, and that this number is expected to rise to more than 5 billion by 2050, and that the world is far from achieving Sustainable Development Goal 6 on water and sanitation.

(Photo DR)