The Hindu/ M Raghuram

Mangalore, Jun 3: The State Government is considering reviving the project to link west-flowing rivers in Dakshina Kannada and Udupi districts. The Paschima Vahini project, which was announced some years ago, is likely to be renamed Sowbhagya Sanjivini.

According to Dakshina Kannada district in-charge Minister B. Nagaraj Shetty, Sowbhagya Sanjivini is the brainchild of State Finance Commission Chairman A.G. Kodgi.

When the Paschima Vahini project was announced in 2002, an expert committee of the Central Water Commission gave an adverse report stating that impounding river water inland would affect the marine environment.

The Central Marine Fisheries Research Institute was also not in favour of the interlinking of the west-flowing rivers.

Free-flowing rivers provide energy for a number of vital processes in downstream estuaries, deltas, and coastal areas that are vital to the fisheries sector. The reduction of river runoff through diversions, impoundment and dams results in major environmental changes in the estuarine ecosystem, researchers pointed out.

The researchers conducted a study in Veraval in Gujarat, Mangalore and Kochi on the west coast and Visakhapatnam on the east coast. Nine river systems — two each in Gujarat, Karnataka and Kerala and three from Andhra Pradesh — were studied.

The riverine-estuarine systems form part of the shelf zones of oceans where contact and interaction between plants and animals and their environment occurs hundred of times faster than on land. Hydrologists and oceanographers in the northern and southern hemispheres have recognised the influences of these changes on the physical characteristics and biological productivity of the coastal areas.

The river inflow, delta outflow system repels saltwater intrusion, flushes natural and human-induced pollutants from the delta and provides a rich supply of nutrients to the estuarine-coastal ecosystems.

Environmental changes

The reduction of runoff by impounding river results in major environmental changes in these ecosystems such as increase in salinity, decrease in organic and inorganic material and sediments, increase in detention time of pollutants and susceptibility of estuarine marine ecosystems to pollutants. This curtails or eliminates the migration route and spawning grounds of shrimps, prawns, molluscs and other organisms.

The Himalayan rivers are snow-fed as well as rain-fed and flow perennially. They discharge about 70 per cent of their inflows into the sea. The rivers of the Deccan, which are rain-fed, shrink to the size of rivulets in summer, and only 30 per cent of the inflows reach the sea.

A seminar organised by the Central Marine Fisheries Research Institute in Mangalore in 2003 concluded that in such a situation the Paschima Vahini and other river-linking projects may be harmful.