Sanchita barua - Guwahati Dialogue, 10th September, 2013
- 1. Sanchita • In a river system, water with their own properties and natural behaviour maintains its own ‘health’, also provides ecological security to their dependent ecosystems and organism therein, offering many economic benefits to the living communities • In maintaining river health, the water quality and quantity is the master variable, which includes natural flow regimes, physico-chemical properties, sediment transport and drainage basin runoff 1
- 2. • Flow regime is of central importance in sustaining the ecological integrity of flowing water systems • The river channel presents a three dimensional form defined by its slope, cross section and pattern. • The natural flow of a river varies on time scales of hours, days, seasons, years and longer • Five critical components of the flow regime regulate ecological processes in river ecosystems: magnitude, frequency, duration, timing and rate of change of hydrologic conditions 2
- 3. These components can be used to characterize entire range of flows and specific hydrologic phenomena, such as floods or low flows that are critical to the integrity of river ecosystems. River ecosystems are adapted to the natural hydrological regime and many components of these systems rely on floods for the exchange, not just of water, but also energy, nutrients, sediments and living organisms.
- 4. HABITAT VARIABILITY OF THE BRAHMAPUTRA RIVER BASIN
- 6. 1. Fast flowing river: This section of the river has a shallow stony bed that harbour small stream fish genera like Nemacheilus, Garra, Barilius, and Danio which hardly grow beyond 15 cm. 52 nos. of species recorded.
- 8. 2. Upstream pools and riffles: These are the sluggish and deeper parts of the river. Species like Tor spp., Labeo pangusia, L. dero, Neolissocheilus hexagonolepis, Raiamas bola inhabit this type of habitat.
- 10. 3. River meandering and confluence: The eddy, counter-current system at the junction of two rivers (tributary and main river) is an ideal place for fish assemblages. The confluences are also the passageways for upstream fish migration. Similarly, the channel meanderings offer suitable habitats for a large number of fish species and river dolphins.
- 11. Open river
- 12. 4. Open river: The main river harbour a wide variety of fish species (167 fish species) and other aquatic fauna including river dolphins (Platanista gangetica).
- 13. Flood plain lakes/wetlands (FPL)
- 14. 5. Floodplain Lakes (FPL): FPL’s are weed infested shallow water bodies temporarily (closed) or permanently connected (open) with the main river. These act as feeding and breeding grounds for many riverine species but do have a ‘residential’ fish population of which air-breathing forms like Channa, Clarius, Anabus, etc. constitute about 40 % of the total species.
- 16. Space between boulders and cobbles
- 17. Livelihood options of BRB Floodplain community people Timber yielding plant Grazing land Transportation Boat and houses Thatching materials Gravel & sand mining 17
- 18. Driftwood collection Fishing activities Community fishing 18 Wetland fishing (wet period) Wetland fishing (dry period)
- 19. Ecological Responses to Environmental Changes
- 20. Ecological Socio-economical Siltation of water bodies Limited agricultural development Eutrophication Limited scope for tourism KEY ISSUES Agricultural Pollution Unemployment Industrial Pollution Loss of productivity Destruction of Biodiversity
- 21. Ecological theory generally states three necessary conditions for natural river functioning (Whittington et al., 2004): Habitat heterogeneity — the biotic community is structured by the availability of habitat and at a broad level there is a relationship between biodiversity and habitat heterogeneity. Connectivity — along the river, with the floodplain and riparian vegetation, and with groundwater; Metabolic functioning — the source and amount of organic matter produced will have a significant effect on the food web.
- 22. The Sustainable Rivers Audit defined river health as: “the degree to which aquatic ecosystems support and maintain processes and a community of organisms and habitats relative to the species composition, diversity and functional organization of natural habitats within a region.” (Whittington et al., 2004).
- 23. • The evaluation of how and to what extent biotic processes can modify the flow of water, nutrients, sediments and pollutants into an aquatic ecosystem has led to the integration of the two branches of science- hydrology and ecology, into a new paradigm ECOHYDROLOGY thereby providing a new insight into the interrelationship of water and biota (Zalewski,1998).
- 24. • An ecohydrological approach to freshwater management maybe summarized as, – Monitoring and control of hydrological processes towards enhancement of resistance and resilience of aquatic ecosystems; – Enhancement of resistance of aquatic ecosystems to anthropogenic stress by restoration of their homeostasis; – River valley and catchment restoration.
- 25. This integrated approach, or ecohydrological approach, creates a new background for the assessment and management of freshwater resources (e.g. river restoration and governance) and accelerates the implementation of new ideas to sustainable development, i.e., elimination of threats and amplification of chances Chances ZONE OF SUCCESS Amplification of chances Elimination of threats Threats Fig 34: Sustainable Management of Freshwater Resources- application of Ecohydrology as a factor of maximizing chances (after Zalewski,1998).
- 26. Improved Water Governance • Analyses of – driving forces, – pressures, – state – impact – response of system components in adherent “what-if?” scenarios.