India's lakes in danger: Alarming drying threatens water security

Global warming and human consumption are causing water depletion in lakes around the world, with more than half of them experiencing a reduction, a new study reveals.

A recent analysis published in the journal Science reveals that more than 30 large lakes in India, including major ones such as Mettur, Krishnarajasagar, Nagarjuna Sagar and Idamalayar, have experienced a drying trend from 1992 to 2020.

The study, conducted by a team international study of researchers, suggests that recent droughts may have contributed to declining reservoir storage in southern India. Lakes, which cover three percent of the world's land surface, play a crucial role in regulating climate through the carbon cycle. However, they often receive less attention and effective management than rivers.

Satellite observations indicate a loss of 90,000 square kilometres of permanent water area worldwide, although the specific drivers of these losses remain unclear. The study used satellite observations and models to analyze trends in lake water storage around the world, attributing the changes to natural factors, climate change and human consumption.

Balaji Rajagopalan, a co-author of the paper and a professor at the University of Colorado Boulder, told Ground Report "The alarming fact that 25% of the world's population, approximately two billion people, reside in a lake basin that is experiencing a declining trend. The findings underscore the widespread impact and urgency to address the problems facing lakes globally".

"The climate signal pervades all factors," said Rajagopalan.

Overall, 53 per cent of the world's largest lakes have been losing water, with 24 per cent seeing an increase. The findings highlight the need to understand the impact of climate change on lake systems and to manage lakes in an integrated manner.

53% lakes reduced in world

According to a study that was carried out on almost 2,000 lakes in the world (combining climatic and hydrological models, using satellite measurements), 53% have reduced their level since 1992.

The study also revealed that lakes such as the Aral Sea (between Kazakhstan and Uzbekistan, although it is more of a salty lagoon) and the Dead Sea (also in Asia and equally salty) have been shrinking due to unsustainable human consumption.

While lakes in Egypt, Mongolia and Afghanistan have shrunk due to rising temperatures. The Caspian Sea and Lake Titicaca between Peru and Bolivia have also been drying up.

The study revealed that it has been lost at a rate of about 22 gigatons per year for 3 decades.

According to information shared by the National Water Commission on March 22, the impacts of drought will primarily damage plants and animals.

Satellite imagery mapping of water

Lead author Fangfang Yao explained the methodology used in the study, stating that they combined satellite imagery mapping of water areas with satellite altimeter data to construct near-monthly time series of lake volumes from 1992 to 2020. By seasonally adjusting the data, they were able to remove seasonal fluctuations before calculating trends.

Yao further emphasized that more than half of the net water loss in natural lakes can be attributed to both direct human impacts, such as human consumption, and indirect human impacts, including climate warming. While the study did not project future trends, Yao mentioned that for the roughly 100 large lakes that are drying up primarily driven by warming, drying trends are likely to continue in warmer weather.

The findings underscore the importance of addressing human impacts and the potential implications of climate change on lake ecosystems.

Fangfang Yao clarified that his study focused on estimating the number of populations residing in basins with dry lakes, rather than quantifying the specific impacts of dry lakes. They found that about a quarter of the world's population lives in these affected basins, highlighting the widespread nature of the problem.

Yao also highlighted the potential consequences of the widespread decline in the lake's water surface. Rising lake temperatures, coupled with lowering water levels, could disrupt the carbon cycle and lead to increased carbon emissions.

He added, "drying lakes can lead to loss of fresh water, environmental degradation (such as receding shorelines, increased salinity, and deteriorating water quality), and negative impacts on activities such as power generation hydroelectric, navigation and recreation".

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