Water

Gangetic dolphins may soon become extinct as river’s natural flow decreases: WII report

The first report on aquatic biodiversity under Namami Gange puts the blame on construction of large-scale hydropower projects 

By Banjot Kaur
Last Updated: Tuesday 25 September 2018
Gangetic Dolphin
Credit: Wikimedia Commons Credit: Wikimedia Commons

The population of Gangetic River Dolphin, granted non-human personhood by the Union government in 2017, is on further decline and may soon become extinct. This warning has come from the first report commissioned under Namami Gange to the Dehradun-based Wildlife Institute of India.

The recently released report says that the population of the Gangetic Dolphin, which was declared national aquatic animal in 2009, is on the verge of extinction due to construction of dams and barrages. Besides, continuous disturbance from movement of large vessels in the river may cause unprecedented decline in dolphin population as has been the case with China’s Yangtze River Dolphin that became extinct. “It is also likely that the modification of the river habitat for navigation, such as dredging, river training and canalisation may damage its habitat,” the report observes. 

During the assessment, the species was sighted in places such as Brijghat and Narora (upstream Kanpur), from Bhitaura to Ghazipur, between Chhapra and Kahalgaon (in Bihar) and in other such places where the depth of the river ranged between 4 and 7 metres. The significant point here is the depth of the river, or in other words, the flow of the river, which is on continuous decline due to hydroelectric projects and dams. Incidentally, last month, a study done by IIT Kharagpur’s Abhijit Mukherjee and others said the water level in River Ganga depleted at a rate of -0.5 cm to -38.1 cm/year between the summer of 1999 and 2013.

Besides Ganges Dolphin, the report also highlights how population of several other aquatic species along the Ganga is continuously going down. The number of otters (only 13 species survive in the world, including three in India) is declining due to construction of large-scale hydroelectric projects, reclamation of wetlands for human settlement and poaching and contamination of waterways. Various species of birds—both resident and migratory—crocodiles, turtles and amphibians are bearing the brunt of human interventions.

Issues in three stretches of the Ganga 

In the upper stretch (Gaumukh to Haridwar), 28.6 per cent of Bhagirathi river channels have turned ‘ecological deserts’; so is the case with 35.2 per cent of Alaknanda channel. This, according to the report, can be attributed to 16 existing, 14 ongoing and 14 proposed hydroelectric projects on the Bhagirathi and Alaknanda river basins—the tributaries of the Ganga. “This is a highly sensitive stretch hosting habitats for endangered species such as otters, the snow trout and the golden mahseer,” the report says. The Tehri dam has led to the decline in golden mahseer population, a fish that features in the red list of International Union for Conservation of Nature (IUCN). Climate change is acting as double whammy for the stretch as the flow in headwaters is vulnerable to the retreat of Gangotri Glacier.

The flow in the the middle stretch of the river (Haridwar to Varanasi) has been reduced to merely 10 per cent of the natural flow, courtesy, water abstraction for various canals in the middle and upper stretches. This stretch hosts gharial, mugger, turtles and island-nesting birds; all of which are getting adversely affected. “Construction and sand mining has disrupted the lateral connectivity of the river,” the report says, pointing to the fact that the stretch has become hotbed for illegal commercial activities. 

Farakka Barrage, according to the report, is the centre of woes when it comes to the lower stretch of the Ganga: Varanasi to Ganga Sagar in West Bengal. “The barrage has changed the salinity regime, water transparency, suspended sediments and altered freshwater fish assemblage,” says the report about the stretch which is habitat for Gangetic River Dolphin, otters, gharials, saltwater crocodile, hilsa and other aquatic species. Most of these are critically endangered species according to IUCN.

Plastic has also caused significant damage to this stretch. “Kolkata produces 2,114 tonnes of solid waste per day of which 10 per cent is plastic. The untreated plastic waste disrupts biodiversity and reaches the Bay of Bengal at a rate of 0.12 million tonnes per year,” the report rues.

The report, however, offers trade-off between the requirement of projects and the flow of the Ganga. “In the Upper Ganga, micro hydel power projects should be considered instead of larger dams,” the report recommends to sustain enough water in the river. The report also says that flow augmentation should be considered in the middle and lower stretches of the Ganga. Flow Augmentation is a calculated release of water stored in reservoirs into the stream to maintain its natural flow. A good flow in the river will also help tackle huge pollution due to abundant dilution of water with the pollutants. 

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