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Home > About Environmental Flows
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 The Context


The flows of the world’s rivers are increasingly being modified through impoundments such as dams and weirs, abstractions for agriculture and urban water supply, drainage return flows, maintenance of flows for navigation, and structures for flood control. These interventions have caused significant alteration of flow regimes mainly by reducing the total flow and affecting the variability and seasonality of flows. It is estimated that more than 60% of the world’s rivers are fragmented by hydrological alterations. This has led to widespread degradation of aquatic ecosystems.

To better understand why natural water flows are important, you may refer to Q&A on environmental flows with Eloise Kendy, director of The Nature Conservancy’s Environmental Flows Programme.

 Ecosystems serve people

Ecosystems provide a wide range of valuable services to people. The degradation or loss of ecosystem services have resulted in economic costs, in terms of declining profits, remedial measures, damage repairs and lost opportunities. The highest costs, however, are typically borne by people depending directly on ecosystem services. These people are generally among the poorest. Recognizing the full value of ecosystem services, and investing in them accordingly, can safeguard livelihoods and profits in the future, save considerable costs and help achieve sustainable development goals. Failing to do so may seriously jeopardize any such efforts.

Cambodia: IUCN/Taco Anema

 Safeguarding ecosystems - the silent water user

Sweden: IUCN/Stefano Barchiesi

Globally, there is a growing acceptance of the need to safeguarding ecosystems when managing waters to meet human demands. A goal of Integrated Water Resources Management (IWRM) is to ensure that the efficient use of water and related resources does not compromise the sustainability of vital ecosystems. This entails finding the balance between the short-term needs of social and economic development and the protection of the natural resource base for the longer term. An important challenge of IWRM is, therefore, to balance water allocation between different users and uses. While economically and/or politically powerful users have relatively well developed methods for quantifying and justifying their water needs, this is not the case for ecosystems – the silent water user. Therefore, ecosystems are frequently omitted from water allocation decision-making.

 Environmental Flows – a key to informed decision making

Many factors, such as water quality, sediments, food-supply and biotic interactions, are important determinants of aquatic ecosystems. However, an overarching master variable is the river’s flow regime. The Natural Flow Paradigm where the natural flow regime of a river is recognised as vital to sustaining ecosystems, has now been widely accepted. This recognition of flow as a key driver of aquatic ecosystems has led to the development of the environmental flows concept. The Environmental Flows concept now serves to enhance informed, equitable and sustainable decision making in water management.

Mexic IUCN/Taco Anema


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