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Water gaps amounting to nearly 458 billion cubic meters per year already exist. These are projected to increase by 6 per cent under 1.5 degrees Celsius warming and by 15 per cent under 3 degrees Celsius warming according to a new analysis published in Nature Communications on January 30, 2025.
Water gaps are defined as the difference between renewable water availability and water consumption while maintaining adequate flows in aquatic environments.
Researchers Lorenzo Rosa (Carnegie Institution for Science) and Matteo Sangiorgio (Politecnico di Milano) used climate outputs from five climate models from the CMIP6 archive to quantify water gaps under baseline, 1.5°C, and 3°C warming scenarios.
These gaps occur on every continent. Global warming is increasingly exacerbating water gaps.
Regions currently experiencing water gaps are expected to face more severe conditions under 1.5°C warming, with even worse outcomes at 3°C warming. This trend is particularly evident in the eastern US, Chile, the Mediterranean region, south and east India, and the North China Plain.
Additionally, some regions that were relatively unaffected in the baseline climate, such as Italy, Madagascar, and some US states on the East Coast (North Carolina and Virginia) and in the Great Lakes region (Wisconsin, Minnesota, Illinois), are projected to see worsening conditions.
Saudi Arabia is projected to experience decreased water scarcity under the 1.5°C warming scenario, but substantial increases in water gaps under the 3°C warming scenario.
The largest water gaps under the baseline climate are found in India, the United States, Pakistan, Iran and China.
“India is projected to experience the most important increase in water gaps under warming scenarios. In a 1.5°C warmer climate, India will have an additional 11.1 km3/yr water gap,” according to the study.
China is the second country with the largest increase in water gaps, followed by Pakistan, the US, Spain and Türkiye.
The study found that different warming levels show uneven changes in water gaps.
In a 3°C warmer climate, India still presents the largest water gap increase compared to baseline conditions, followed by Pakistan, the US, China, Spain and Türkiye.
Global warming will alter precipitation patterns, leading to a reduction in water gaps in some countries. For instance, in Nigeria, “water gaps are projected to decrease from 1.2 km3/yr under the baseline climate to 0.8 km3/yr and 0.6 km3/yr under 1.5 °C and 3 °C warming, respectively”.
Other countries expected to see decreases in water gaps under warming include the Philippines, Sudan, Vietnam, Uzbekistan, the United Arab Emirates, Tajikistan, and Ethiopia.
The analysis also looked at water gap trends in major hydrological basins. Under baseline climate conditions, the largest water gaps are found in the Ganges-Brahmaputra, Sabarmati, Tigris-Euphrates, Indus and Nile River basins.
Under 1.5°C warming conditions, water gaps are expected to increase the most in the Ganges-Brahmaputra, Godavari and Mississippi-Missouri river basins, while water gaps are expected to decrease in the Sabarmati, Columbia and northwestern United States and Nile basins.
In a 3°C warmer climate, the Ganges-Brahmaputra basin still presents the largest water gap increase compared to baseline conditions, followed by the Indus, Mississippi-Missouri, China Coast, Godavari and Tigris-Euphrates basins.
The study also looked at major irrigation regions suffering from water gaps. They included California’s Central Valley, the US High Plains, Central Chile, the Iberian Peninsula, Saudi Arabia, the Tigris-Euphrates River system, the Aral Sea Basin, the Indo-Gangetic Plains of India and Pakistan, the North China Plain, and Australia’s Murray-Darling Basin.
“About 4 billion people reside and about half the world’s irrigated agriculture is in regions that experience water scarcity for at least one month each year, said the study's author Lorenzo Rosa.
The study emphasised on developing a more resilient and sustainable water management system to combat water scarcity. This could include investing in resilient infrastructure, enhancing water storage capabilities, desalination of seawater, reuse of treated wastewater and physical and virtual water transfers to distribute water from areas of abundance to areas of need.
In an editorial Sunita Narain, Director General, Centre for Science and Environment talked about how water supply should be linked to the system of sanitation and wastewater generation.
A village in Uttar Pradesh is an example of how greywater could be used to combat local flooding and recharge groundwater. Manpur Ojha uses silt chambers, soak pits and kitchen gardens to turn water from washing areas and kitchens into a valuable resource.