Around 3.6 billion people have problems accessing water at least one month a year, a figure that could rise to more than 5 billion by the middle of the century, according to a report by the World Meteorological Organization (WMO).

The report on the availability of drinking water on the planet, released this Tuesday, is the first that the WMO has dedicated specifically to water resources and highlights that in 2021 two thirds of the earth's surface had river flows below the average of the last 30 years, while only one third was above or at average levels.

At a time of growing demand for this liquid element and limited supply, water is also related to 74% of natural disasters (droughts, floods, storms), points out the document released by the United Nations agency.

"The impacts of climate change tend to manifest themselves through water, with more intense and frequent droughts, more extreme floods, more irregular seasonal rainfall and accelerated glacial melting," stressed WMO Secretary General Petteri Taalas during the presentation of the report.

The study highlights as areas where the river flow was below average in 2021 the Río de la Plata and the south and southeast of the Amazon in South America, or the basins of the Colorado, Missouri and Mississippi rivers in North America.

In Africa, there was also a below-average flow in the Niger, Volta, Nile and Congo rivers, while in Eurasia the same occurred in the basins of Siberia, other parts of Russia and Central Asia.

In contrast, above-normal flows have been recorded in some basins in North America, the northern Amazon, rivers in southern Africa (such as the Zambezi and Orange) and others in China and India, countries that have recently suffered major floods.

Some of the areas where the water supply is at critical levels see their situation aggravated by the over-exploitation of groundwater, the report warns.

The document also analyzes the cryosphere, the ice at the poles, mountains and glaciers, which is the world's largest reserve of fresh water as it is the source of rivers and supplies for 1.9 billion people.

The WMO also warns of worrying thaws in areas such as Alaska (North America), Patagonia (South America) and the Himalayas (Asia).