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Additional than 50 per cent of the world’s biggest lakes and reservoirs have shrunk more than the previous 3 decades mainly due to climate adjust and human activities, according to a new study. From these water bodies, around 600 cubic km of water was lost involving 1992 and 2020 — an quantity equivalent to the total water utilized in the United States for the complete year of 2015.

It also noted that far more than half of the reservoirs situated in peninsular India have witnessed substantial water storage decline, primarily due to sedimentation. In addition, amongst the worst impacted organic lakes in the nation is Ladakh’s Tso Moriri.

Published in the journal Science final week, the study, ‘Satellites reveal widespread decline in worldwide lake water storage’, has been carried out by Fangfang Yao, Ben Livneh and Balaji Rajagopalan, from the Cooperative Institute for Analysis in Environmental Sciences (University of Colorado Boulder, USA), Yoshihide Wada from Climate and Livability Initiative (King Abdullah University of Science and Technologies, Saudi Arabia), Jean-François Crétaux and Muriel Berge-Nguyen, from Laboratory of Space Geophysical and Oceanographic Research (France).

The continued shrinking of lakes, Yao and Rajagopalan told The Indian Express by e-mail, has led to a decline in freshwater provide, atmosphere degradation and deterioration of water top quality for humans and livestock. Meanwhile, water shortage beyond a specific level in reservoirs of hydroelectric dams could adversely effect the generation of hydroelectricity.

Central Asia’s Aral Sea has substantially dried due to unsustainable water consumption. On the left is a satellite image taken in 2000 and on the correct is an image clicked in 2018. (Photo: NASA Earth Observatory)

If lakes are encroached upon (such as the case in India with smaller sized lakes), they disappear as a water supply but also contribute to serious urban flooding. Loss of lake levels leads to groundwater pumping and depletion, major to a host of other troubles.,” Rajagopalan added.

How was the study carried out?

For their study, Yao and his group examined 1,975 of the world’s biggest lakes, such as 1,052 organic lakes and 921 reservoirs — researchers studied lakes which are bigger than one hundred sq km and reservoirs with far more than 1 cubic km of storage capacity. The evaluation was carried out following a novel methodology that involved combining two-dimensional water places with 1-dimensional water levels to estimate the 3-dimensional adjust in water storage.

“We utilized 250,000 lake-region snapshots captured by satellites involving 1992-2020 to survey the region of 1,972 of Earth’s most significant lakes. We collected water levels from nine satellite altimeters and utilized extended-term water levels to lower any uncertainty. For lakes with out a extended-term level record, we utilized current water measurements produced by newer instruments on satellites.,” Yao explained.

“Combining current level measurements with longer-term region measurements permitted us to reconstruct the volume of lakes dating back decades.,” he added.

What are the findings of the study?

The researchers discovered that out of the 1,052 organic lakes that have been examined, 457 had important water losses in the previous 3 decades. Meanwhile, 234 organic lakes gained water and 360 of such water bodies didn’t show any notable trend.

They attributed 57 per cent of the net decline in the water quantity in organic lakes to human activities, such as unsustainable consumption of water, and rising temperature and prospective evapotranspiration (PET) — loss of water due to each evaporation and transpiration — with the latter two indicating the part of climate adjust.

The study also pointed out the worst impacted biggest lakes across the globe and why they are shrinking in size. For instance, the Aral Sea in Central Asia, Lake Mar Chiquita in Argentina, the Dead Sea in the Middle East, and the Salton Sea in California have primarily dried due to unsustainable water consumption. Whereas, rising temperature and PET brought on the full disappearance of Lake Gowd-e-Zareh in Afghanistan, Toshka lakes in Egypt, and marked drying of Lake Kara-Bogaz-Gol in Turkmenistan, Lake Khyargas in Mongolia, and Lake Zonag in China.

The Arctic lakes have shrunk as a outcome of a “combination of modifications in precipitation, runoff, temperature, and PET, which are most likely a concurrent outcome of organic variability and climate adjust.,” researchers stated in the study. Notably, lakes have shrunk or disappeared fully across 82 per cent of the Arctic’s lake-wealthy regions in the previous 20 years, as per a 2022 study.

In India, apart from Tso Moriri Lake, Andhra Pradesh’s Pulicat Lake and Kolleru Lake have been impacted but they didn’t function in the study as they have been “below our threshold so did not make it in our analyses,” Rajagopalan told The Indian Express.

An additional acquiring is that contrary to prior research, organic lakes situated in humid tropics and higher altitudes are also experiencing water shortages.

In addition to this, the most recent paper pointed out that two-thirds of all reservoirs across the globe have seasoned important storage declines. Reservoirs, on the other hand, showed a net worldwide boost in water levels, owing to 183 lately filled reservoirs. The key cause behind the drop in water levels is sedimentation — the approach of particles such as sand and stones settling to the bottom of a physique of water.

“Our acquiring suggests that sedimentation is the major contributor to the worldwide storage decline in current reservoirs and has a bigger effect than hydroclimate variability, i.e., droughts and recovery from droughts,” the researchers stated.

What are the consequences of shrinking lakes?

According to the study, practically two billion persons, 1-quarter of the worldwide population in 2023, will be impacted as they reside in basins with substantial water bodies that have witnessed a important drop in their water levels in the previous 3 decades.

“Many of these drying lakes have been identified as significant sources of water and power (hydropower).,” the researchers stated in their paper. The decreased size of these lakes not only final results in freshwater decline and environmental degradation but also disrupts the water and carbon cycles.

Widespread water shortage in these water bodies, “particularly accompanied by increasing lake temperatures, could lower the quantity of absorbed carbon dioxide and boost carbon emissions to the atmosphere offered that lakes are hotspots of carbon cycling.” the study added.

How can we conserve these water bodies?

Yao and Rajagopalan stated to save the shrinking lakes, there is a need to have to handle them in an integrated manner. Measures like restrictions on water consumption and climate mitigation to bring down worldwide temperatures are some of the strategies to conserve them. This will also support in decreasing sedimentation in reservoirs as the price of sedimentation is linked to climate adjust — it increases when there is intense precipitation, as properly as land disturbance such as wildfires, landslides and deforestation.

“This (managing lakes in an integrated manner) will elevate the status of lakes to their rightful spot, And they can continue to sustain humanity. We take care of them, they will take care of us, the ecology in a life-affirming manner.,” Rajagopalan stated.

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