WMO Report On World Water Resources: 2023 Was Either Too Dry Or Too Wet

Third report on the state of global water resources published / Record low water levels in the Mississippi and Amazon basins

The year 2023 was not only marked by unprecedented heat, but also by severe drought in many parts of the world - while flooding occurred elsewhere. The World Meteorological Organization (WMO) has published its third report on the state of global water resources. According to the information, 2023 was the driest year in the past 33 years, followed by 2021 and 2015. "2023 was much drier than we expected," said Prof. Dr. Robert Reinecke of Johannes Gutenberg University Mainz (JGU). Reinecke heads the Earth System Modeling group at the JGU Institute of Geography and contributed to the preparation of the report.

The third report on world water resources takes an even more comprehensive look at the global water cycle than the first two reports. In particular, this time the storage capacities of lakes and water reservoirs as well as the cryosphere, i.e. snow and glaciers, were recorded in more detail. More data and more models for analyzing the data thus provide an even more accurate picture of the current situation. The results for 2023 continue to show a significant deviation from the historical normal value of the reference period 1991 to 2020. "More than 50 percent of the catchment areas show deviations from this reference period," says Reinecke. The river discharge volumes - a key indicator of water resources - were predominantly below normal values. According to the WMO report, record low water levels were recorded in the Mississippi and Amazon basins. Extremely low snow storage also meant that less water was available in the spring and therefore less water could flow away, which was particularly important for European rivers. "The global loss of glacier mass, which the current WMO report puts at 600 gigatons of water, is worrying," said the earth system scientist. "This is the largest loss in the past five decades."

2023 will be either too dry or too wet globally
There was some recovery in groundwater, for example in South Africa. However, the availability of groundwater in North America and Europe has noticeably decreased as a result of prolonged drought. "However, we can assume that the situation in Central Europe will be somewhat better in 2024," expects Reinecke. In terms of soil moisture, there was great drought in North and South America, while moisture levels far above normal were measured in places like New Zealand and Russia.

In summary, the core message of the report, according to Reinecke, is that globally there are still significant deviations from normal values: "Either too dry or too wet, neither is good. Unfortunately, we can expect to experience both extremes more often as temperatures rise worldwide." The year 2023 was hotter than ever before, 1.45 degrees Celsius above pre-industrial levels.

Reinecke was instrumental in the preparation of the WMO report in cooperation with Dr. Hannes Müller Schmied, a researcher at the Goethe University Frankfurt and the Senckenberg Biodiversity and Climate Research Center Frankfurt (SBiK-F), and the Global Runoff Database Center (GRDC) in Koblenz. Together they contributed model results and methodology. Prof. Dr. Robert Reinecke's Earth System Modeling group also contributed specifically to the methodology for analyzing the groundwater data in the report. In order to better understand the changes in groundwater levels in climate change, Reinecke's team is currently building a global data set.

Research within the framework of the Rhine-Main Universities
The research is carried out within the framework of the Alliance of Rhine-Main Universities (RMU), which includes the Goethe University Frankfurt, the Johannes Gutenberg University Mainz and the Technical University of Darmstadt as renowned research universities. With a framework agreement in December 2015, this long-standing partnership was expanded into a strategic alliance in order to strengthen the scientific performance of the universities, jointly improve study programs and shape knowledge transfer and networking with society.