Environmental Flows

by

Ryan Morrison, Erin Bray

• LAST REVIEWED: 31 July 2019
• LAST MODIFIED: 31 July 2019
• DOI: 10.1093/obo/9780199363445-0116

Introduction

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.

General Overviews

The works in this section provide overviews and general introductions to environmental flows. A brief introduction to environmental flows is provided in Acreman 2016. Arthington, et al. 2018 and 10th International River Symposium and International Environmental Flows Conference 2007 are foundational texts that highlight international consensus about the importance of environmental flows. Tharme 2003, Acreman, et al. 2014, and Petts 2009 give examples of environmental flow methodologies and management approaches used in the United States and globally. The ecological and geomorphic implications of altered hydrology are highlighted by the meta-analysis in Poff and Zimmerman 2010, and Poff, et al. 2017 provides suggestions for improving environmental flow science by including dynamic hydrologic and ecological principles. Discussions of how environmental flow science may change due to future conditions are provided in Acreman, et al. 2014 and Laizé, et al. 2014. The sole book dedicated to describing environmental flow science is Arthington 2012.

• Acreman, Mike. 2016. Environmental flows: Basics for novices. WIREs Water 3: 622–628.

  DOI: 10.1002/wat2.1160

  Provides a short introduction to environmental flows, including basic definitions, examples of frameworks, and a discussion of how environmental flows may change in the future.

• Acreman, Mike C., Angela H. Arthington, Matthew J. Colloff, et al. 2014. Environmental flows for natural, hybrid, and novel riverine ecosystems. Frontiers in Ecology and Environment 12.8: 466–473.

  DOI: 10.1890/130134

  Discusses whether the extensive modification of river systems requires a new approach to environmental flows. Specifically, this work argues that a “designer” approach may be required to sustain river systems based on the socioeconomic values of society.

• Acreman, Mike C., and Michael J. Dunbar. 2004. Defining environmental river flow requirements? A review. Hydrology and Earth System Sciences Discussions 8.5: 861–876.

  DOI: 10.5194/hess-8-861-2004

  Describes general categories of methods used to determine environmental flows, including look-up tables, desktop analysis, functional analysis, and hydraulic habitat modeling. This work also includes descriptions of some common environmental flow frameworks.

• Arthington, Angela H. 2012. Environmental flows: Saving rivers in the third millennium. Berkeley: Univ. of California Press.

  DOI: 10.1525/california/9780520273696.001.0001

  Provides a comprehensive overview of environmental flows, including a description of river hydrology, river ecology, and methods of determining environmental flows. The book also includes information about aquatic systems less commonly considered in environmental flow science, such as estuaries.

• Arthington, Angela H., Anik Bhaduri, Stuart E. Bunn, et al. 2018. The Brisbane Declaration and Global Action Agenda on Environmental Flows (2018). Frontiers in Environmental Science 6: 45.

  DOI: 10.3389/fenvs.2018.00045

  Updates the original Brisbane Declaration and Global Action Agenda to address progress made in environmental flow science and contemporary challenges. This study makes thirty-five recommendations for implementation environmental flows through legislation, research, and water resource management.

• Laizé, C., M. C. Acreman, C. Schneider, et al. 2014. Projected flow alteration and ecological risk for pan-European rivers. Rivers Research and Applications 30.3: 299–314.

  DOI: 10.1002/rra.2645

  Assesses the changes in flow regimes throughout Europe due to future climate conditions. This work provides an important look at possible flow alterations and subsequent changes in river ecosystems in Europe.

• Petts, Geoffrey E. 2009. Instream flow science for sustainable river management. JAWRA: Journal of the American Water Resources Association 45.5: 1071–1086.

  DOI: 10.1111/j.1752-1688.2009.00360.x

  Reviews approximately thirty years of environmental flow science and describes current approaches as of 2009. Describes the importance of linking hydrologic, geomorphic, and biological expertise to successfully implement environmental flows.

• Poff, N. Leroy, Rebecca E. Tharme, and Angela H. Arthington. 2017. Evolution of environmental flows assessment science, principles, and methodologies. In Water for the Environment: From policy and science to implementation and management. Edited by Avril C. Horne, J. Angus Webb, Michael J. Stewardson, Brian Richter, and Mike Acreman, 203–236. Cambridge, MA: Academic Press.

  DOI: 10.1016/B978-0-12-803907-6.00011-5

  This book chapter provides the most current analysis of contemporary environmental flow methods and frameworks. It also makes suggestions for updating environmental flow science by considering non-stationarity of hydrologic and ecological regimes, including dynamic fluxes and rates of ecological processes and populations.

• Poff, N. Leroy, and Julie K. H. Zimmerman. 2010. Ecological responses to altered flow regimes: A literature review to inform the science and management of environmental flows. Freshwater Biology 55.1: 194–205.

  DOI: 10.1111/j.1365-2427.2009.02272.x

  Thorough literature review of the links between flow alterations and ecological responses. The paper quantifies ecological responses to changes on flow magnitude, duration, frequency, rate or change, and timing if data are available. Available online by purchase or subscription.

• The 10th International River Symposium and International Environmental Flows Conference. 2007. Environmental flows are essential for freshwater ecosystem health and human well-being. The Brisbane Declaration and Global Action Agenda. Brisbane, Australia, 3–6 September 2007.

  Provides the seminal definition of environmental flows. This declaration, based on the consensus of water managers and scientists around the world, highlights the importance of environmental flows and outlines steps for implementation.

• Tharme, R. E. 2003. A global perspective on environmental flow assessment: Emerging trends in the development and application of environmental flow methodologies for rivers. River Research and Applications 19.5–6: 397–441.

  DOI: 10.1002/rra.736

  Synthesizes global efforts in environmental flow science and characterizes the major methodologies used to study and implement environmental flows. The paper emphasizes the need for holistic approaches that can be used in developing countries where hydrology data are sparse.