Skip to main content

Indian deltas are sinking

Indian deltas are sinking, and no, it is not because of sea level rise. “Humans are sinking deltas four times faster than the sea level is rising,” says American professor of oceanography and geology at the University of Colorado, James Syvitski.

A proliferation of large dams that starve deltas of sediment, groundwater mining that causes land compaction, and artificial levees that affect river courses, have been responsible for the subsiding of major Indian deltas including Ganga-Brahmaputra, Krishna-Godavari, Brahmani and Mahanadi, Prof. Syvitski demonstrated in his lecture ‘The Peril of Deltas on the Indian Subcontinent: Welcome to the Anthropocene,’ at the International Geosphere-Biosphere Programme held here recently. “The Krishna delta is perhaps the worst off because large dams are preventing almost any of the river’s sediments from reaching it,” he later told The Hindu. In a research paper co-authored by Professor Syvitski and published in Nature Goescience in 2009, satellite imagery and on-ground studies established that the Krishna delta has witnessed a 94 per cent reduction in sediment deposition.

The Godavari, Brahmani and Mahanadi deltas have seen a 40 per cent, 50 percent and 74 per cent reduction, respectively, in sediments delivered to them over the last three decades. “Globally, on average, we have built one large dam everyday for 130 years. Hundreds of gigatonnes of sediments are stored in these global reservoirs,” he said.

And India, which started earlier than even the U.S., has seen a particular proliferation of dams post 1950. “A delta typically should have enough sediment to counter ocean energy. But if you stop bringing in sediment, eventually the ocean will win." The Ganga delta, meanwhile, is sinking at 18 mm a year, even as the sea level rises by 3 mm a year along this coast, spelling a tenuous future for the thousands of people who live and work, he said.

Here, groundwater mining has led to a significant compaction and subsidence of land over the last 15 years. He concurs with the concept of ‘Anthropocene,’ a term suggesting that human impact on the environment has been so large post industrial revolution that this era can be counted as an entirely new geological epoch. And the submergence of deltas is indeed a case in point, he said.

Comments

Popular posts from this blog

SC asks Centre to strike a balance on Rohingya issue (.hindu)

Supreme Court orally indicates that the government should not deport Rohingya “now” as the Centre prevails over it to not record any such views in its formal order, citing “international ramifications”.

The Supreme Court on Friday came close to ordering the government not to deport the Rohingya.

It finally settled on merely observing that a balance should be struck between humanitarian concern for the community and the country's national security and economic interests.

The court was hearing a bunch of petitions, one filed by persons within the Rohingya community, against a proposed move to deport over 40,000 Rohingya refugees. A three-judge Bench, led by Chief Justice of India Dipak Misra, began by orally indicating that the government should not deport Rohingya “now”, but the government prevailed on the court to not pass any formal order, citing “international ramifications”. With this, the status quo continues even though the court gave the community liberty to approach it in …

Cloud seeding

Demonstrating the function of the flare rack that carries silver iodide for cloud-seeding through an aircraft. 
Water is essential for life on the earth. Precipitation from the skies is the only source for it. India and the rest of Asia are dependent on the monsoons for rains. While the South West Monsoon is the main source for India as a whole, Tamil Nadu and coastal areas of South Andhra Pradesh get the benefit of the North East Monsoon, which is just a less dependable beat on the reversal of the South West Monsoon winds.

India’s criminal wastage: over 10 million works under MGNREGA incomplete or abandoned (hindu)

In the last three and half years, the rate of work completion under the Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA) has drastically declined, leading to wastage of public money and leaving villages more prone to drought. This could also be a reason for people moving out of the programme.

At a time when more than one-third of India’s districts are reeling under a drought-like situation due to deficit rainfall, here comes another bad news. The works started under the MGNREGA—close to 80 per cent related to water conservation, irrigation and land development—are increasingly not being completed or in practice, abandoned.

Going by the data (as on October 12) in the Ministry of Rural Development’s website, which tracks progress of MGNREGA through a comprehensive MIS, 10.4 million works have not been completed since April 2014. In the last three and half years, 39.7 million works were started under the programme. Going by the stipulation under the programme, close to 7…