Varanasi ghats sinking due to over exploitation of groundwater, reveals BHU study

New Delhi: Some of Varanasi's iconic ghats are sinking, according to a new study that shows land subsistence along the Ganga riverfront, primarily due to the impact of relentless groundwater depletion coupled with erosion caused by a meandering river.

While the historical city has recorded an annual subsistence of 2-8 mm along the riverfront, the cumulative effects are most prominent and even visible near the ghats, visited by lakhs daily. At some ghats, for example, some of the steps leading to the water have become deformed.

In six years between February 2017 and August 2023, the popular Manikarnika Ghat near the Kashi Vishwanath temple and Dashashwamedh Ghat sank by more than 23 mm, says the study carried out by geologists at Banaras Hindu University.

The cumulative subsistence is over 50 mm in six years at Samne ghat and Prahlad ghat whereas it is more than 33 mm in Gaay ghat and Chousatti ghat. The sinking is little less in Assi ghat, Raja Harishchandra ghat, Raja ghat and Chet Singh ghat.

“Too much groundwater is being extracted adversely affecting the underground sand layer, which in turn compresses the clay layer, causing irreversible deformation. Our data clearly shows such subsistence since 2017, but groundwater depletion may be happening for a long time,” Ashwani Raju, first author of the research paper, told DH.

The scientist said Varanasi witnessed rapid urbanisation in recent years as people migrated from rural areas in search of a better life. This has put immense pressure on the ground water level.

According to the Central Ground Water Board, the city has nine administrative areas, out of which in three the ground water level is in “over-exploited” condition where in five the level is “semi-critical”. But even then the most groundwater loss happens in the over-exploited zone.

“The recharge of the aquifers by the monsoon is low as the rate of extraction is more than the rate of recharge,” said Raju, who along with other BHU colleagues and scientists from Chapman University, USA, examined the problem in detail using extensive satellite data. The monsoon rainfall is on a declining trend for the last 21 years between 1998 and 2018.

The study involves 12 Ghats – all showing subsistence trends - and four other areas that too are sinking at a rate of 3-5 mm every year.

At Samne Ghat which has an annual lowering rate of 8 mm and sunk by more than 52 mm since 2017, the meandering Ganga adds an additional factor. This is an area where the river takes a sharp bend in high velocity towards left while flowing towards the north east. “The rate of erosion and soil under-cutting is very high,” he said.

With subsistence being also reported from other Indo-Gangetic plain cities like Delhi, Lucknow and Kolkata, the BHU scientists said the results of the study should be included in framing water management strategies as climate change would seriously impact water resources in the future.

The study has been published recently in the journal Science of the Total Environment.