Gangetic Dolphin Population Affected
The declared river dolphin as the National Aquatic Animal of India on October 5 last year and the International Union for Conservation of Nature (IUCN) red-listed it as an endangered animal in 1996. Following this, the Gangetic dolphin was included in the Schedule-I of the Indian Act, 1972.
Researchers Dr Debojit Baruah of the Department of Botany, Lakhimpur Girls’ College and Lakhi Prasad Hazarika, of the Zoology Department, North Lakhimpur College, said, while talking to The Assam Tribune, that the LSHEP dam may be responsible for complete annihilation of the Subansiri dolphin species. They are doing research on the present environmental and biodiversity status of the downstream of Subansiri river basin, riparian zone and forests, assessing the pre- impact of the 2000 MW Lower Subansiri dam.
They alleged that the National Hydroelectric Power Corporation (NHPC, the implementing agency of the LSHEP, had deliberately avoided inclusion of Gangetic Dolphin in the environment impact assessment (EIA) report of the project for easy environmental clearance.
Moreover, the NHPC authorities have repeatedly been committing serious violations of both the Forest Conservation Act 1980, and the Environment Impact Assessment Notification, 1994 of theGovernment of India.
These violations have led to increased sediment load in the Subansiri downstream. The sediment load comparison is made taking 2003 as the base year, when the construction of the LSHEP dam was not started. The data for the purpose were collected mainly at Chawldhowa Ghat.
Increased sediment load has compelled the dolphins to change their original territory. The migration of the dolphins towards the deeper regions of the down stream during the lean period in 2009 is an indicator of river health degradation caused by sediment dumping.
The sediment load on the river increased by 39.21per cent and 43.65 per cent in 2008 and 2009 respectively in comparison to 2003.
A recent survey conducted under the research project, indicates that there are now 29 Gangetic dolphins (Platanista gangetica gangetica Roxburgh) in the downstream of the river. In 2006, there were 21 dolphins in these areas. The year-round sufficient discharge— minimum 252 to 550 cubic metres per second (cumecs) in lean period itself— of the river provides the primary survival condition for the animal.
As a whole, dolphins are usually sighted in the confluence point with the Brahmaputra and in certain spots like confluence of river Dikrong, Ranga, Luit etc with the Subansiri.
Unregulated Subansiri maintains downstream hydrology by longitudinal connectivity, facilitates adequate, biologically productive water, and creates a safe habitat for the dolphins.
Greater richness and diversity of preferred prey fishes like Aorichthys, Wallago, Eutropiichthys, Clupisoma (Ahri, Bheu, Borali, Vacha, Neria) make the Subansiri more suitable habitat for this aquatic mammal.
The awareness of the entire down stream people of the riversystem makes it a safe haven for the dolphins.
However, the LSHEP EIA report says that after commissioning of the hydroelectric project in 2012, only 6 cumecs of water will be released to maintain the down stream flow for 20 hours in a day. This massive reduction in down stream flow discharge, will wipe out the Gangetic dolphins from the Subansiri forever, warned the researchers. (LSHEP) has posed a serious to the Gangetic population in Subansiri, claim two researchers working on a major UGC project on the eco-system of . They also called for long-term strategies to save this precious aquatic animal.