Inland Fisheries

3.5.5 Strategies to be followed before taking up river linkage project

The following strategies are the recommendations emerged from the deliberations took place in the National Academy of Agricultural Sciences organized Round Table of “Impact of interlinking of river basins” held during 21-22, May 2004.

Data mining: Large volume of raw data on water quality, productivity, aquatic ecology and fish biodiversity are available for river systems from various parts of the country. Most of these data are not properly analysed and interpreted. Hence, there is an urgent need for data mining and analysis to gather base line information on water quality, aquatic ecology, productivity and fish biodiversity for various river systems.

Modelling studies and scenario analysis: Software-aided modelling studies are required to assess the impact of changes in river runoff on water chemistry, productivity, aquatic ecology, biodiversity and fish production. The impact of interlinking of river basins on fisheries will vary from one river system to another and from region to region. Hence, detailed scenario analysis and simulation studies have to be carried out for each of the river systems to assess the impact under varying flow conditions.

Scaled-down approach: Before initiating large-scale river basin linking at national, level, it will be appropriate to conduct studies on linking adjacent river systems with 10 similar ecosystems. Such scaled-down approach will be very useful to assess and understand the environmental impacts of river linking on aquatic ecosystem.

Environmental flow: Environmental flows may be broadly defined as the 'provision of water for freshwater-dependent ecosystems to maintain their integrity, productivity, services and benefits in cases when such ecosystems are subject to flow regulation and competition from multiple water users. There is an urgent need to assess the minimum environmental flow in donor rivers. It is anticipated that the knowledge base created through this process will strengthen the level of understanding of methodologies available for use, their relative strengths and deficiencies, and their potential for application under various circumstances.

Loss-gain statement: There is an urgent need to work out a loss gain statement on the possible impact of interlinking of river basins on fisheries, using the available data.

River ranching: River ranching of fishes is being carried out in various parts of the country by different agencies. It is necessary to evaluate the usefulness of river ranching for enhancing the fish production in our river systems. River ranching with fish seed in altered scenario needs to be addressed in a proper perspective.

River siltation and dredging: The siltation pattern in donor and receipt rivers could change due to interlinking. Heavy siltation of rivers, canals and lakes is already an acute problem in the Himalayan region. There is urgent need to assess the usefulness of river bed dredging for improving the river ecology and fish production.

Impact on estuarine and coastal waters: River run-offs provide energy for a number of vital processes in downstream estuaries, delta and coastal areas. These processes include transport of nutrients, organic matter and nutrient-rich silt, oxygen enrichment, entrainment of nutrients in bottom sediments, dilution and flushing of pollutants, etc. The most widely discussed and well-documented impacts of large scale hydrological alterations (river damming and river diversion, for example) on marine systems are reductions in water and sediment discharge. Immediate attention should be given to study the impact of altered river flow due to river interlinking on biodiversity pattern of estuarine and coastal fauna.

Biodiversity studies: It is necessary to study and identify the endangered species which could become extinct due to interlinking. Based on existing biodiversity lists of exotic and native species, it is necessary to identify the prevalent differences between the rivers likely to be linked and project the post-linking scenario.

Taxonomic studies: Taxonomists and taxonomy related studies are required to assess and document the aquatic biodiversity patterns. Hence, there is an urgent need to give stress to taxonomic studies and developing human resources in the field of taxonomy.