Altered hydrological cycle poses long-term threat for millions’ water security
Representative photo: iStock The circulation of water in the Earth-Atmosphere system has been significantly impacted by climate change and human activities, according to the World Meteorological Organization (WMO). The effect on the hydrological cycle are leading to droughts and extreme rainfall events and the erratic water cycles unleashed widespread disruption, burdening livelihoods and economies.
The ongoing melting of snow, ice and glaciers compounded the threat, exacerbating the risk of extreme weather events such as floods. These events cast long-term consequences on the water security of millions, warned WMO’s State of Global Water Resources 2022 report, released on October 12, 2023.
The findings of the report are critical, as nearly four billion people are already experiencing severe water scarcity for at least a month every year.
The Asian Water Tower (AWT), the world’s largest reservoir of ice and snow after the Arctic and Antarctic regions, saw significant glacial melting in 2022. This altered the natural downward flow of major rivers — the Indus, Amu Darya, Yangtze and Yellow River — in the region, the document pointed out.
AWT covers the Third Pole, which includes the Tibetan Plateau, the Himalayas, the Karakorum, the Hindu Kush, the Pamirs and the Tien Shan Mountains.
The increasing pace of glacial melting in AWT, which provides a reliable water supply to almost two billion people, highlighted the deepening influence of climate change on regional water resources.
“Glaciers and ice cover are retreating before our eyes. Rising temperatures have accelerated — and also disrupted — the water cycle,” WMO Secretary-General Petteri Taalas said in a statement.
“A warmer atmosphere holds more moisture. We are seeing much heavier precipitation episodes and flooding. And at the opposite extreme, more evaporation, dry soils and more intense droughts,” he added.
The risks of such glacial events were evident in India as well. North Sikkim witnessed devastating glacial lake outburst floods after the South Lhonak Lake burst on October 4, 2023.
From 2000-2018, the total glacier mass in the AWT decreased by approximately 4.3 per cent. This led to a significant reduction in snow cover, shortening the snowmelt season. The number, total area and volume of glacier lakes have increased rapidly as a whole, pushing the lake’s water by approximately 16 per cent of the total volume, said the report.
The snow cover in the Alps remained well below the 30-year average during the 2023 spring despite late snowfalls in May, as observed in the basins feeding the four major rivers — Rhine, Rhone, Danube and Po.
The situation was more severe in the Po River, where water levels were seven feet lower than usual, according to media reports. Five regions in Italy were under a drought emergency as the region faced the highest drought severity in 2022.
The report also flagged deviations in the courses of rivers. The volume of water flowing through the rivers was lower than the normal. In 2022, over 50 per cent of the global catchment areas experienced deviations from normal river discharge conditions.
For instance, in Europe, the flow of rivers has decreased in summer owing to a major heatwave, drought and La Nina. Now, with El Nino in 2023, the hydrological cycle is likely to be impacted further, warned the document.
The Horn of Africa experienced severe drought, affecting 21 million people’s food security. As a result, the volume of water in rivers flowing through the region was below the normal in 2022. The Congo River and the entire catchment of the Nile River in Central Africa exhibited reduced river discharge.
As rivers dried up, the impacts were also visible across water reservoirs. Over 60 per cent of major water reservoirs saw below or normal inflow. This challenges water availability in an increasingly changing climate.
However, a smaller proportion of basins exhibited above-normal and much-above-normal conditions, said the document. This was evident from the cases from Africa mentioned in the report. Areas like the Niger Basin and coastal areas of South Africa saw above-average discharge and major flood events in 2022, it said.
For instance, the catastrophic floods and landslides in the provinces of KwaZulu-Natal and Eastern Cape after the country witnessed exceptionally heavy rainfall in 2022.
Given such contrasting and overwhelming water-related disasters, including drought and floods, water management and monitoring lies at the heart of the global Early Warnings For All initiative that ensures everyone on Earth is protected by early warnings by 2027.
“Many countries targeted for priority action in Early Warnings for All suffered from major floods or droughts in 2022 and no country had timely and accurate hydrological data available to support evidence-based decision-making and early action,” said Taalas.
The report called for enhanced data sharing to enable meaningful early warnings and more coordinated water management policies that are integral to climate action.
Mid-way to 2030, when the world is far off from achieving sustainable development goal (SDG) 6: Clean Water and Sanitation, the report’s findings contribute towards informed decision-making relevant to the Sustainable development goals.
It emphasised SDG 13 (climate adaptation) by focusing on climate-related impacts on water systems and calling for mitigation actions.
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