Over 3 billion people have water supply problems for one month every year, a number that could increase to 5 billion by the middle of the century, according to a report on the availability of freshwater by the World Meteorological Organization published on Tuesday.

In the document, the first dedicated to the state of global water resources, the WMO underlined that in 2021 two-thirds of the Earth’s surface had river flows below the average of the past 30 years, while only one-third was above or at average levels.

The report also said that water is related to 74% of global natural disasters, like droughts, floods, and storms.

“The impacts of climate change are often felt through water — more intense and frequent droughts, more extreme flooding, more erratic seasonal rainfall, and accelerated melting of glaciers,” WMO secretary-general Petteri Taalas said at the report’s presentation.

The WMO chief warned that these natural disasters have “cascading effects on economies, ecosystems, and all aspects of our daily lives.”

Among those areas most affected by the low water flows in 2021 were the Rio de la Plata and the south and southeastern Amazon, South America, or the basins of the Colorado, Missouri, and Mississippi rivers in North America.

Africa also saw a decrease in its streamflows in the Niger, Volta, Nile, and Congo rivers. In Eurasia, the same occurred in basins in Siberia, other parts of Russia, and Central Asia.