Inland Fisheries

3.5.4.2 Negative impacts

· Loss of habitat: River interlinking might affect fish feeding and breeding habitats in the rivers and lakes in the water donor zones due to lowering of water volume and enhanced siltation load. The flood plains and wetlands connected with donor rivers would also be affected. River run-offs provide energy for a number of vital processes in downstream estuaries, delta and coastal areas. Reduced river discharge could result in loss of coastal habitats such as mangroves, coral reefs, sea grasses, estuarine and delta regions.

· Water quality changes: Significant changes in water quality of rivers, lakes, estuaries and coastal waters could occur due to changes in sediment load, nutrients and contaminant levels. The levels of toxicants and contaminants in donor rivers may go up owing to reduction in self-purifying functions subject to changes in flow regimes.

· Loss of biodiversity: Each river system has distinct groups of biota different from other water bodies. When environment is altered, they are affected, with particular threat to endangered and endemic species. The linkage of rivers could also lead to loss and homogenisation of genetic diversity of fishes.

· Changes in land-ocean interactions: River is a critical component of the delta­estuary-coastal sea ecosystem. Un-impounded rivers provide energy for a number of vital processes in downstream estuaries, delta and coastal areas, upon which healthy fisheries are dependent. The linkage of rivers could alter the timing and quantity of river discharge into the sea, which may alter the river-mediated land­ocean interactions and coastal fisheries. A recent study conducted by Central Marine Fisheries Research Institute, Kochi, on 'Impact of Dams on River into Sea and Changes in the Coastal Waters' has shown that reduction in river discharge into the sea will adversely affect the water chemistry and productivity profile of coastal waters and the estuarine fisheries.