Living Rivers: Environmental Flows

By: Staff Reporter
Increasing global exploitation of fresh water has led to drying up of rivers at several places. The socio-economic consequences of disruption and collapse of riverine systems are often profound as people are much more dependent on natural riverine services than is immediately apparent. In response the concept of environmental flows has been developed in the recent decades.

Voices in the global economy are today increasingly talking about water-related risks as an emerging threat to businesses. There is growing evidence that freshwater biodiversity is suffering acutely from over abstraction, from pollution of rivers, lakes and groundwater and from poorly planned water infrastructure. As the global population grows and demand for food and energy increases, the pressure on freshwater ecosystems will intensify. To add to this, the main effects of climate change are likely to be felt through changes in the hydrological cycle.

Freshwater systems are home to 40 per cent of all fish species in less than 0.01 per cent of the world’s total surface water, and when water-associated amphibians, reptiles and mammals are added to the fish totals, they together account for as much as one third of global vertebrate biodiversity. At the same time, people need to use rivers, lakes and wetlands for many things – water to drink, irrigate, industrial water supply, water repurification, fishing, boating, recreation and cultural activities. If we are careful, rivers can do all these and more. But people see rivers only as suppliers of water and as drainage ditches. Environmental flows are aimed at keeping at least some of the natural flow patterns along the whole length of a river, so that people, animals and plants downstream can continue to survive and use the river’s resources. Thus, environmental flows are really about using water resources fairly.

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Environmental Flow Requirements

River habitats are generally controlled by physical processes (flow, water quality, sediment transport) so we can make big changes to the biodiversity of rivers by managing (or mismanaging) the flow. Rivers have varied flow patterns – some flow permanently, some seasonally, and some desert streams only once every few years. The biodiversity of different rivers, and different parts of rivers, varies with these physical patterns.

Flows are the main driver of biodiversity in rivers. Except for a few very large ones, rivers are variable and unpredictable, so the animals and plants that live in them have to be able to deal with sudden extremes such as floods and droughts. As a result, most river ecologists agree that the communities of animals and plants found in riverine ecosystems are largely controlled by physical rather than biological processes, which include water quality, sediment dynamics, and flow. Flow is the main driver of biodiversity in rivers – it creates the aquatic habitats, it brings the food down from upstream, it covers the floodplain with water during high flows, and it flushes the sediment and poor water quality through the system. River channels have been formed over geological time and are a long-term function of the flows. The type of channel and floodplain also dictates the physical habitats that will be available for the riverine flora and fauna.  Bunn and Arthington, 2002 suggest the principles that – flow is the major determinant of physical habitat in streams; riverine species have evolved primarily in response to natural flow regimes; flow connectivity throughout the river and its floodplain are essential to the maintenance of riverine populations; and, altered flow regimes facilitate the growth and spread of introduced species. A recent World Bank, 2008 document has characterised flows as a ‘master variable’ in freshwater systems.


Environmental Flow Assessment

An environmental flow is an amount of water that is kept flowing down a river in order to maintain the river in a desired environmental condition. As the concept has evolved, there has been significant development of approaches to the assessment of environmental flows. From global experiences a number of key lessons may be drawn.

  1. The characteristics and ecosystems of rivers are controlled in a very significant way by physical processes, in particular flows. An environmental flow regime describes all the different flows (wet season, dry season, floods, droughts etc.), that are needed to keep the river and all its aspects functioning at a desired condition.
  2. Environmental flow assessment is both a social and a scientific process, with a social choice at its core. There is no one correct environmental flow regime for rivers – the answer will depend on what people want from a river. Different sorts of rivers are likely to have different requirements and priorities. For example, there would be differing approaches for a river in a protected area in contrast to a river in a major irrigation or urban area. Choice and judgement, particularly when deciding on environmental objectives, are an essential part of the environmental flow process.
  3. Environmental flow assessment is based on the assumption that there is some ‘spare’ water in rivers that can be used without unacceptably impacting the ecosystem services that the river provides.
  4. Environmental flows are not just about establishing a ‘minimum’ flow level. All of the elements of a natural flow regime, including floods and droughts, are important in controlling the characteristics and natural communities in a river. For example rivers with a constant flow regime can quickly become dominated by pest species.
  5. Environmental flows don’t always require an increase from present flows. In some cases, where low season flows have been artificially increased by inter basin transfers or releases from dams for hydropower, the environmental flow recommendations may be for lower flows than present. In other cases, the assessment may identify that some further water can be abstracted without unacceptable impacts.
  6. There are now over 200 methods for assessing environmental flows. Some are quick modelling or extrapolation methods, requiring minimal extra work; others require years of fieldwork and specialists from a number of disciplines. The five main categories of assessment are: look up table approaches; extrapolation approaches; hydraulic rating methodologies; habitat simulation methodologies; and, holistic methodologies.
  7. Instead of undertaking extensive prior assessment, an important alternative approach may often be to concentrate immediately on implementation of some flows. This option then requires careful monitoring of the results of trial flows, to see whether they meet objectives and is likely to be particularly important in situations where there is already an acute problem of over abstraction.
  8. In all contexts, implementing environmental flows should be an adaptive process, in which flows may be successively modified in the light of increased knowledge, changing priorities, and changes in infrastructure (such as removal of dams) over time. From this perspective, it may be more appropriate for legislation to require implementation but allow flexibility in the methods of assessment.
  9. Lack of information, and lack of resources, should never be a barrier to implementation of environmental flows. Some attempt to restore some of the natural flow variability is always better than none, and fine-tuning is always possible as more knowledge and resources become available.
  10. In almost any context, implementation presents an immeasurably greater challenge than assessing the necessary flows. Conservationists therefore need to ensure that they do not devote a disproportionate amount of effort to discussion and debate over the appropriate environmental flow methodology, neglecting the more important effort of working for implementation.


Implementing Environmental Flows

Implementing environmental flows requires difficult decisions about reducing present uses, and depends on social and political will, and economic priorities. There has been enormous development of environmental flow assessment methods, but relatively little implementation.

Assessment of environmental flows is about predicting what sort of flow regime will be necessary to achieve any particular ecological state in a river. Implementation is actually getting the required water down the river at the appropriate time. In any context, implementation presents an immeasurably greater challenge than assessing the necessary flows. Throughout the countries in the world that have set policies for environmental flows, its probably fair to say that the assessment of flow requirements has always run far ahead of implementation. Especially in over allocated rivers, this requires difficult decisions and actions, such as reducing water use, or building additional storage. In addition to significant problems of political will or finance to implement environmental flows, there can also be practical problems. For example, dam outlets may not have the capacity to deliver necessary flow volumes. The consequences of this mismatch between ambition and reality can be seen in the fact that several hundreds of environmental flow assessments have been undertaken, compared with only a handful of successful implementations worldwide.


A Scientific and Social Process

Environmental flow assessment is a combination of scientific and social elements – scientists can do the best assessment of flow needs, but they won’t be implemented unless people know why the flows should be left in the river, and think that it is important to do so. The most effective way of getting the science accepted is to embed the environmental flows process in an overall basin management process, which combines the use of the river with its protection.

Environmental flows ultimately depend on the social, economic and political will of the stakeholders to make them work. Better scientific understanding is more likely to convince the people. Environmental flow was developed as an eco-hydrological process in the 1970’s and 80’s. There was a gradual realisation in the 1980’s that there needed to be a social component and the stakeholders needed to be part of the process. But, it wasn’t until the 1990’s and the new millennium that there has been a full realisation that environmental flow assessment is a social process with an eco-hydrological core, rather than an eco-hydrological process with a social add on.

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Policy and Legislation

Many countries now have a legal requirement for environmental flows with the increasing need to look after their natural resources. Many others have an implicit requirement prominent among these are the countries of the European Union (EU), for which the EU Water Framework Directive requires the achievement of ‘good’ ecological conditions for all water bodies by 2015, but no specific requirement for environmental flows. Such legislation rarely provides careful instructions on how the environmental flows are to be calculated or achieved. The pioneering South African Water Act of 1998 requires water to be ‘reserved’ for basic human needs and for the environment, and for a classification system to be developed. The Act and its associated parliamentary white papers mention the need for ‘sustainability’, ‘sustainable management’, ‘sustainable ecosystems’ etc., but without any operational definition of what this entails or how managers should measure whether they are achieving this. Similarly, the US Water Pollution Control (Clean Water) Act of 1972 requires water managers to ‘evaluate, maintain and restore the chemical, physical and biological integrity of the nation’s waters’, but without a quantifiable methodology, managers are often at a loss to know whether or not they are in contravention of the law. The EU Water Framework Directive makes an attempt to define the limits of its classes ‘high, good, moderate, and poor’, but ultimately the definition has to be developed on a water-body by water-body basis, in relation to the natural range of conditions for each.

Implementation in the Indian Context

The importance of environmental flows has been recognised by the Indian Government in its various environment related policies. However, till recently boards, agencies and authorities developing water resources under the Water Act, 1974 and Environment (Protection) Act, 1986 have been mainly concerned with the monitoring of water quality deterioration and is responsible for prevention and control of pollution. The National River Conservation Directorate (NRCD) under the Ministry of Environment and Forests (MoEF) was also mandated with monitoring of water quality. The MoEF in collaboration with the Ministry of Water Resources constituted a Water Quality Assessment Authority (WQAA) in 2001 to standardise water quality monitoring methods and take up research and development activity related to water quality management. This was perhaps the first time that an Action Plan was drawn up to include optimum water abstraction and maintain minimum discharge in the riverine system. Working Groups constituted under WQAA also undertook several assessment studies of environmental flows of various rivers of the nation.

In 2009, the constituting of the National Ganga River Basin Authority, has brought the issue of environmental flow to the fore, as one of its sub-components is to engage in modelling exercises and scientific assessment studies of the minimum environmental flow of the river Ganga.

However, as far as implementation is concerned, India is far behind. Public interest litigation for the river Yamuna submitted to the Supreme Court way back in 1992 elicited a response that pointed towards the need to have a minimum sustainable flow in the said river. Commander S D Sinha of Paani Morcha, the petitioner, pleaded for enforcement of measures to stop pollution in Yamuna from Delhi and sought orders to permit fair levels of water flow in the Yamuna. He argued that the Union Government had no right to approve plans that kept the river dry for almost nine months in the year. The Supreme Court fixed an arbitrary flow level in its ruling, but it failed to resolve the problem.

Maintaining an environmental flow for any river in India throws up several issues. Policy makers recognising the need for such flows insist that biological characteristics with species survival ratio should be taken into account as opposed to physical and chemical characteristics – linking it directly with sustainable livelihood options. Also, researchers feel that no single value of ecological flow may be determined for the entire length of the river in the Indian context. The pattern and quantum of flow will vary from location to location. Thus, the parameters of environmental flows should be stretch specific. This is bound to further complicate the process of implementation especially when several riparian states flanking rivers rarely arrive at any consensus regarding river sharing.

Environmental flows can be undertaken through various measures. Rain water harvesting, ground water recharge, water conservation and recycling are a few that are already in operation. However, catchment area storage project, a mega investment proposition still at its conceptual stage, once commissioned will store runoff in the upper catchment areas to maintain environmental flow in the lean summer months.

 Source Keeping Rivers Alive, A Primer on Environmental Flows, Jay O’Keffe, Tom Le Quesne, February 2009, WWF

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