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‘Dams hinder a river’s natural cycle’

15 November 2010

PANAJI: Construction of dams on rivers hinders their natural cycle and release of nutrient-enriched water stored in reservoirs for several months into the estuaries increases carbon emissions in the rivers and adversely impacts their eco-systems, NIO scientists said.

“When the water is stored in the reservoir for six to eight months, nutrients enriched due to high bacterial respiration of organic carbon have an impact on the water quality,” NIO scientist V V S Sarma said.

In a presentation at the annual meeting of Indian academy of sciences, Bangalore held at Dona Paula, Sharma said impounding water in dams cuts off the river’s natural flow and blocks tidal flushing. “When the stored water is released, it affects the coastal eco-systems,” he said. Organic matter like plankton decomposes due to stagnation of water and this leads to an increase in the dissolved carbon dioxide.

Further, when the water enters the estuaries, this leads to generation of more carbon dioxide, thereby increasing the carbon emissions in the estuary.

Goa has three major dams, Selaulim on Guleli nadi of river Sangam with a catchment area of 209 sq kms and gross command area of 29,373 hectares, Anjunem dam on Costi nadi, a tributary of Valvanti river with a potential of 4,600 hectares and the Tillari irrigation project in Maharashtra, a joint venture between Goa and Maharashtra aimed at irrigating 16,978 ha in Goa and 6,676 ha in Maharashtra is part of the Chapora riverine system. The Amthane dam in Bicholim and Chapoli in Canacona are smaller projects located on other tributaries.

The impacts of dams on rivers have, however, not been studied, M Dileep Kumar, another NIO scientist admitted. “Attempts have been made in the past to study minor to major estuarine systems along the Indian coastline, but an effort to synthesize this information into a holistic framework is missing,” he said.

NIO scientist M D Zingde said the concentration of human habitat on the banks of estuarine systems are threatening the health of these systems, affecting availability and quality of food resources. A little more than half of the sewage discharged in the estuaries is treated. “Most estuaries in India do not meet water quality criteria for fecal coliform (100/100ml) set by Central Pollution Control Board,” he said.

NIO director S R Shetye explained special features of Indian estuaries, including Mandovi river while D Shankar and A C Anil, also NIO scientists spoke about nature of freshwater influx and influence of monsoon on rivers.

Read more: http://timesofindia.indiatimes.com/city/goa/Dams-hinder-a-rivers-natural-cycle/articleshow/6926362.cms#ixzz15L24Dq00

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Written by csirindia

November 15, 2010 at 2:05 pm

Posted in NIO

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