ENVIRONMENTAL FLOWS : CONCEPTS AND METHODS

Environmental flows are critical for maintaining ecosystems.The flow regime of a river can be divided into base flows, small floods that occur every year, and occasional large floods that spread out onto floodplains. Identifying these flow components—and understanding the ecosystem consequences of their loss or modification —is central to a flow assessment. This notes introduces concepts and methods for determining environmental flow requirements for rivers, including a description of how different sorts of river flows contribute to the maintenance of rivers, the practicalities of undertaking a flow assessment, the need for balancing environmental and offstream demands for water, and the challenges faced in implementing environmental flows.