The United Nations World Water Development Report 2022 on groundwater, a synthesis

This paper is a synthesis of the 2022 250-page United Nations Report on groundwater (https://unesdoc.unesco.org/ark:/48223/pf0000380721), which accounts for 99% of liquid fresh water on Earth and is the source of one-quarter of all the water used by humans. Many of the world's largest cities, and numerous smaller cities and towns, rely on groundwater. The report presents an overview of the regional presence and use of, and demand for, groundwater. It relies on a synthesis of 700 bibliographic references. Very useful figures are gathered on water resources and uses. The report barely touches on the role of geology, and hydrogeological expertise in preparing the report would have been helpful. More explanations of various hydrogeological aspects would have been useful, such as underground 20 watersheds and basins, runoff, flow rates, the water cycle (large and small), vertical water exchanges, and groundwater flow inertia which helps populations to adapt to annual and seasonal fluctuations. The variability in atmospheric components (e.g. meteorological variability) is more often dominated by the climate change question. This intellectual approach puts groundwater under the influence of atmospheric effects, which leads to an alarmist discussion of multiple aspects: abnormal water table drawdown or increase, exposure to surficial pollutions, and many negative aspects of saltwater intrusion in coastal aquifers. the bibliographical references in the report can be found following the page numbers of the document, cited in parentheses here. The very numerous bibliographical sources are responsible for some contradictions or errors. Some economic elements are almost ignored, such as bottled water and thermalism in 35 relation with groundwater, and North-South cooperation pre-1990, although many positive results related to this period are depicted, which have greatly helped to improve methodologies.