Environmental Flows

Environmental flows are commonly defined as the river-flow characteristics necessary to maintain the integrity of riverine ecosystems. The concept of environmental flows has evolved over the past half-century, beginning with the development of minimum instream flows necessary to protect a single fish species to current frameworks for holistically including all aspects of river health that depend on natural flow regimes. This also includes the interaction of terrestrial environments with riverine ecosystems during large flooding events. The challenges associated with defining and implementing environmental flows are numerous, and they sometimes lack data necessary to define flow-ecology relationships, appropriate temporal and spatial scales for environmental flow applications, and incorporate environmental flows into water management policy. Given these challenges, researchers and practitioners have made incredible advances in better understanding the relationships between river health and flow dynamics, including the links among flow, sediment, temperature, and human activities. In addition, computational advances have allowed researchers to more accurately model flow-habitat relationships at fine scales, providing a more complete understanding of the connection between flow and habitat needs for riverine species. All these advances benefit from holistic frameworks that guide environmental flow development and applications while considering the needs of other water uses in a river system. This article presents relevant studies regarding approaches for developing environmental flows, relationships between riverine ecology and flow dynamics, and policy frameworks and tools useful for implementing environmental flows in practice.