Most of the world was drier than normal in 2021, with “cascading effects on economies, ecosystems and our daily lives”, according to UN World Meteorological Organization(WMO).
The area with below-average streamflow was approximately two times larger than the above-average area, in comparison to the 30-year hydrological average, said the agency’s first report on global water resources — State of Global Water Resources report.
STREAMFLOW AND DRY AREAS
In the report, the WMO said that areas unusually dry included South America’s Rio de la Plata area, where a persistent drought has affected the region since 2019. In Africa, major rivers such as the Niger, Volta, Nile and Congo had below-average water flow in 2021. The same trend was observed in rivers in parts of Russia, West Siberia and in Central Asia.
“On the other hand, there were above-normal river volumes in some North American basins, the North Amazon and South Africa, as well as in China’s Amur river basin, and northern India,” the WMO said.
In Africa, rivers such as the Niger, Volta, Nile and Congo had below-normal discharge in 2021, along with parts of Russia, West Siberia and in Central Asia. WMO said that 3.6 billion people have inadequate access to water at least one month per year and that this is expected to increase to more than five billion by 2050.
WMO Secretary-General Prof. Petteri Taalas said, “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 – with cascading effects on economies, ecosystems and all aspects of our daily lives. And yet, there is insufficient understanding of changes in the distribution, quantity, and quality of freshwater resources.”
“The State of Global Water Resources report aims to fill that 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 Prof. Taalas.
The report gives an overview of river flow, as well as major floods and droughts. It provides insights into hotspots for changes in freshwater storage and highlights the crucial role and vulnerability of the cryosphere (snow and ice). The WMO also said that 3.6 billion people now faced inadequate access to water at least a month per year. This is expected to increase to more than five billion by 2050. “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,” the report said.
TERRESTRIAL WATER STORAGE
“In 2021, terrestrial water storage was classified as below normal (in comparison to average calculated from 2002-2020) on the West coast of the USA, in the central part of South America and Patagonia, North Africa and Madagascar, Central Asia and the Middle East, Pakistan and North India,” the WMO said in the report.
The report mentioned that it was above normal in the central part of Africa, the northern part of South America, specifically the Amazon basin, and the northern part of China.
On a longer-term basis, the report pointed out several hotspots with a negative trend in terrestrial water storage. These include Brazil’s Rio São Francisco basin, Patagonia, the Ganges and Indus headwaters, as well as south-western USA.
In contrast, the Great Lakes Region exhibits a positive anomaly, as does the Niger basin, East African Rift 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 Alaska, Patagonia and the Himalayas.
The cryosphere (glaciers, snow cover, ice caps and, where present, permafrost) is the world’s biggest natural reservoir of freshwater. Mountains are often called natural “water towers” because they are the source of rivers and freshwater supplies for an estimated 1.9 billion people.
Changes to cryosphere water resources affect food security, human health, ecosystem integrity and maintenance, and leads to significant impacts on economic and social development. Such changes also cause hazards such as river flooding and flash floods due to glacier lake outbursts.
With rising temperatures, the annual glacier run-off typically increases at first, until a turning point, often called ”peak water”, is reached, upon which run-off declines. The long-term projections of the changes in glacier run-off and the timing of peak water are key inputs to long-term adaptation decisions.
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.