The concept of environmental flow appears unscientific, dangerous too
Freshwater has been the main fuel for human civilisations and economies. But unscientific overuse of rivers, lakes and groundwater aquifers has led to degradation of water bodies to such an extent that their ecosystem services are increasingly failing. The term “environmental flows” has come into circulation as a result of searches to reverse the situation.
The way the term is used creates an impression that water can be extracted from rivers, lakes and aquifers without hurting their ecological integrity as long as environmental flows, or e-flow, are left for meeting the needs of ecosystems. A scientific analysis would help resolve emerging conflicts between large-scale water extraction and stability of aquatic ecosystem processes and services.
Among the very early articulations on e-flow is an IUCN (the International Union for Conservation of Nature) report. It says in a pristine situation the flow in a water body goes to support aquatic ecosystems and related processes. If a substantial part of this flow is extracted for meeting social needs and economic demands, the balance goes to support ecosystems and related services. This is the e-flow, arrived through a trade-off negotiated among diverse stakeholders. Depending on the nature of ecological and economic priorities, e-flow may be kept at the pristine level or substantially reduced. This reduced flow will support ecosystems partially and extracting parties will pay for the sub-pristine functioning of aquatic ecosystems. Hence, there is nothing like a fixed amount of e-flow.
Several professionals have also started making assessments of environmental flows. For all Indian rivers, a study has identified 25 per cent of the total annual renewable water resources of the country as e-flow. It needs to be stressed that human knowledge has not even identified all ecosystem processes associated with flows of water in rivers, lakes or aquifers, not to speak of their ecological water needs. All extraction, small or large, would have an impact on the ecological status of the sources and related ecosystems.
Environmental flows can be assessed on the basis of the water needs of specific ecosystem processes and services but they constitute only a small part of the totality of ecosystem processes and services. For example, flows are needed to facilitate the production of fish, as in the case of hilsa in the lower Ganga basin. It also generates sediment loads in the uplands and transports them to the floodplains and the delta, creating fertile land for humans and habitat for aquatic biodiversity. Floodplains receive crucial groundwater recharge from high flows. Flood flows flush heavier sediments out to the deltas and coasts, clearing the riverbed. These are important ecosystem services for human survival and need adequate flows for their continuation. E-flow needed for maintaining such individual ecosystem functions and services can be approximated by modelling. However, if the functions and services are seen in their totality, the e-flows will be similar to their natural annual flows devoid of any water abstraction.
The point is to find an agreeable trade-off in which the abstraction of water will be socially acceptable, ecologically sustainable and the ecosystems would exist with some damage but not get fatally degraded. Unfortunately, the existing project assessment procedures in India cannot be called scientific from such holistic perspective. There is a tendency for promoters of water extraction projects to disregard ecological linkages and deprive people whose livelihoods are impacted.
In the absence of a deeper scientific understanding, vested description of e-flow may aim at getting a blanket approval for extraction of water from the flow of rivers, lakes or aquifers, without paying the genuine compensation. We must remember environmental flows do not mean free lunches for any water extraction project.
Jayanta Bandyopadhyay is professor at IIM-Calcutta
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