Flooded villages, shrinking glaciers and cracks in dry arable land: the global water cycle is becoming increasingly out of balance, which means there is often either too much or too little water locally. The causes of increasing water extremes are climate change and human activities. This emerges from a new report from the UN World Meteorological Organization (WMO) on the global status of water resources. The information it contains about the water level is intended to help society and politics recognize the impending dangers and prevent serious consequences if possible.
At the end of November 2022, the World Meteorological Organization (WMO) presented the first report on the status of global freshwater resources for 2021. Now the WMO has presented its “State of Global Water Resources Report” for the second time, this time for 2022. The latest report includes significantly more detailed data on the global water cycle, including the inflow and outflow of almost 1,000 rivers and Lakes, groundwater levels, soil moisture and evaporation rates from land areas in 14 countries as well as water levels in the form of snow and ice.
This data came from both manual field research and satellite remote sensing. However, because the global information situation on these aspects, especially groundwater, is not sufficient, the report is also based on hydrological models and simulation data on global water resources in the past year. In total, 273 measuring stations, around eleven international modeling groups and dozens of researchers contributed their expertise under the coordination of the WMO. The last 30 years served as a comparison period for the current water level.
Global extent of drought in 2022
According to the report, large parts of the world experienced drier conditions in 2022: almost 40 percent of the areas examined suffered from more drought than the average in previous decades. “The flow in many rivers around the world was significantly below the normal amount,” says co-author Robert Reinecke from the University of Mainz, describing a consequence of the low rainfall. The soil was also less moist in many places than in the past due to heat waves. According to the report, due to ongoing water withdrawal at the same time, the groundwater levels were lower than in the reference period.
And there were also serious changes in the cryosphere, the world of frozen water: from 2000 to 2018, the glacier mass of the so-called third pole around the Himalayan mountains fell by more than four percent. The snow cover decreased significantly and the volume of glacial lakes fed by meltwater increased sharply. The decline in snow and ice in the Alps last year was similarly serious, with consequences for the surrounding rivers.
The drought in 2022 has left its mark worldwide, including in Europe, as the report shows: The Rhine, the Danube and the Po carried very little water for a long time, with corresponding consequences for river shipping. France struggled with low rainfall, which affected the cooling of nuclear power plants. South America also experienced severe drought, which meant that drinking water became scarce in Paraguay on several occasions and the drought around the La Plata River, which has been ongoing since 2020, was intensified. Africa suffered regional humanitarian crises from droughts and floods elsewhere. In Australia, groundwater levels in the important Murray-Darling catchment continued to fall below normal levels despite increasing rainfall. According to the WMO, there was too little data from Asia, the Middle East and parts of Africa to make clear statements about water resources.
Climate impacts and water resources
According to the report, a major cause of the disturbed water balance is climate change. Rising temperatures have accelerated and disrupted the water cycle. This is because a warmer atmosphere retains more moisture, which results in more frequent and severe rainfall and flooding. However, these are not evenly distributed in space and time, so that dry phases and floods alternate. During extreme periods without precipitation, climate change causes more water to evaporate, resulting in drier soils and more intense droughts.
The water level often also influences how severe the consequences of climatic fluctuations and changes are: heat and dryness, for example, can promote fires that spread more quickly due to a lack of soil moisture. Melting snow, ice and glaciers during heat periods not only increase the risk of flooding in the short term, but also endanger the long-term water supply security for many millions of people. Droughts and extreme rainfall, together with other climate impacts, claim many lives and have serious consequences for the economy.
The report provides a comprehensive overview of current water resources worldwide and highlights the impact of climate change. “The WMO report also serves as a basis for political and economic decisions by highlighting crisis potential and crisis regions,” says Reinecke. It thus enables investments in better water and crisis management. According to the WMO, the report on global water levels should be published annually in the future in order to always provide detailed and up-to-date data for a better basis for decision-making. For example, next year's report is expected to analyze the change in climate influences from La Niña in 2022 to El Niño in 2023, which is likely to have significant impacts on the water cycle.
Source: World Meteorological Organization (WMO), State of Global Water Resources 2022