On Nov 29, 2022, the World Meteorological Organization (WMO) has published its first State of Global Water Resources report to assess the effects of climate, environmental and societal change on the Earth’s water resources. The aim of this annual report is to support monitoring and management of global freshwater resources in an era of growing demand and limited supplies. For report and other related materials, see: https://public.wmo.int/en/our-mandate/water/state-of-global-water-resources
The first edition of the report looks at streamflow – the volume of water flowing through a river channel at any given time. It also assesses terrestrial water storage – all water on the land surface and sub-surface and the cryosphere (frozen water).
The information and accompanying maps are largely based on modelled data (to achieve maximum geographical coverage) and remotely sensed information from NASA’s GRACE (Gravity Recovery and Climate Experiment) mission for terrestrial water storage. The modelled results were validated against observed data, wherever available).
The report shows how large areas of the globe recorded drier than normal conditions in 2021 – in spite of the a La Niña event and above average South West Monsoon rainfall in India. Globally, the area with below-average streamflow was approximately two times larger than the above-average area, in comparison to the 30-year (1990-2020) hydrological average. Approximately one third of the areas analysed was in line with the 30-year average.
“The State of Global Water Resources report aims to fill the knowledge gap and provide a concise overview of water availability in different parts of the world. This will inform climate adaptation and mitigation investments as well as the United Nations campaign to provide universal access in the next five years to early warnings of hazards such as floods and droughts,” said WMO Secretary-General Prof. Petteri Taalas..
Between 2001 and 2018, UN-Water reported that 74% of all natural disasters were water-related. The recent UN climate change conference, COP27, urged governments to further integrate water into adaptation efforts, the first-time water has been referenced in a COP outcome document in recognition of its critical importance.
Streamflow Large areas of the globe recorded dryer than normal conditions in 2021, compared to the average of the 30-year hydrological base period. In Africa, rivers such as the Niger, Volta, Nile and Congo had less than normal discharge in 2021. Similarly, rivers in parts of Russia, West Siberia and in Central Asia had lower than average discharge in 2021. There was above normal river discharge in some Northern American basins, the North Amazon and Southern Africa (Zambezi and Orange), as well as China (the Amur river basin) and northern India. Page 11 of the report says: “In India, headwaters of the Ganges River were characterized by above- to much above-normal discharge.”
Terrestrial water storage for the years 2002–2021 for Asian river basins Indus, Ganges and Brahmaputra from the WMO report is given in figure below.
Significant flood events with numerous casualties were reported, among others, from China (Henan province), northern India, western Europe, and countries impacted by tropical cyclones, such as Mozambique, the Philippines and Indonesia.
Terrestrial water storage Terrestrial water storage is all water on the land surface and in the subsurface. In 2021, terrestrial water storage was classified as below normal (in comparison to average calculated from 2002-2020) in the North India and Pakistan, among others. It was above normal in the central Africa, Amazon basin, and north China.
On a longer-term basis, the report pointed out several hotspots with a negative trend in terrestrial water storage. These include the Ganges and Indus headwaters. In contrast, the Great Lakes Region exhibits a positive anomaly, as does the Niger basin, and North Amazon basin.
Overall, the negative trends are stronger than the positive ones. Some of the hotspots are exacerbated by over-abstraction of groundwater for irrigation. The melting of snow and ice also has a significant impact in several areas including the Himalayas.
The Cryosphere The cryosphere (glaciers, snow cover, ice caps and, where present, permafrost) is the world’s biggest natural reservoir of freshwater.
Lack of reliable Data The report highlights the lack of accessible verified hydrological data. WMO’s Unified Data Policy seeks to accelerate the availability and sharing of hydrological data, including river discharge and transboundary river basins information. Future assessments in the WMO State of Global Water Resources will provide the incentive to regularly assess changes in the cryosphere and the variability of water resources, at basin and regional level.
Says Prof Taalas in forward to the report: “WMO is committed to extending the variables in future editions of the report to include groundwater, soil moisture and water quality. Once the WMO Hydrological Status and Outlook System (HydroSOS) is operational, the annual State of Global Water Resources report can be produced as a direct output of this system.”
SANDRP (ht.sandrp@gmail.com)
SANDRP 