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Environmental Flow

Science, Policy, and Implementation. Environmental Flow. Eric S. Hersh CE397 January 31, 2008. environmental flow definition. Brisbane Declaration 2007.

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Environmental Flow

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  1. Science, Policy, and Implementation Environmental Flow Eric S. Hersh CE397 January 31, 2008

  2. environmental flow definition Brisbane Declaration 2007 “The quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend on these ecosystems”

  3. Ecological functions (goods and services) • Fish and wildlife: habitat, migration, reproduction, biodiversity • Endangered species protection • Fisheries (commercial and recreational) • Navigation • Hydropower • Recreation • Waste assimilation • Water supply • Food supply • Flood and drought mitigation • Nutrient delivery • Sediment transport • Coastal salinity regulation • Aesthetics

  4. interdisciplinary nature • Engineering: hydrology, hydraulics, water quality • Biology and ecology • Geomorphology and physical processes • Policy and regulation

  5. transboundary nature • Basin-wide management scale • Transboundary difficulties in prescribing and regulating environmental flow needs • Disparities in water availability and need, infrastructure, technical capacity, environmental awareness, regulatory structure

  6. human impact

  7. human impact • Artificial higher or lower low flows • Erratic daily flows from hydropower demand • Prevent or minimize floods • Disconnect floodplain • Channelize rivers and alter habitat • Eliminate variability

  8. Guadalupe Rv abv Comal Rv at New Braunfels, Daily Maximum Flow Trinity Rv nr Rosser, Daily Minimum Flow

  9. historic river resource protection • Water quality • U.S. Clean Water Act, 1972 • Designated uses, water quality criteria • “The objective of this Act is to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters” • Water quantity • Minimum flow (flat line) • “…nothing in this Act shall be construed to supersede or abrogate rights to quantities of water which have been established by any State.”

  10. flow- “the master variable” • Controlling factor in riverine physical, biological, and chemical processes • e.g.: water temperature, dissolved oxygen, available habitat, spawning cues, channel shape, substrate type

  11. Question: manage flow for…?

  12. Answer: everyone.the natural flow regime Poff et al 1997 (Postel and Richter, 2003)

  13. Rate of Change Magnitude Duration Timing the natural flow regime Not depicted: frequency

  14. the big question… How much water does a river need?

  15. water allocation 20th century Ecosystem support allocation 21st century what is this sustainable boundary? (Postel and Richter, 2003)

  16. Texas: Legislation • Senate Bill 2 (2001): the science bill • Establish and maintain an instream flow data collection and evaluation program • Develop methodologies to determine flow conditions in Texas rivers and streams necessary to support a sound ecological environment • Senate Bill 3 (2007): the implementation bill • Establishes the who, when, and how of environmental flow implementation in Texas • TCEQ must adopt the recommended standards by September 1, 2010

  17. Texas: Methods • Lyons Method(Bounds and Lyons 1979) • Used in permitting • Based on a percentage of monthly median flow • Oct to Feb: 40% • Mar to Sept: 60% • Consensus Criteria for Env Flow Needs (CCEFN) (TCEQ 1997) • Used in planning • Percentage of monthly naturalized flow from WAM • Nat Q > median Q  protect median Q • 25th %ile < Nat Q < med Q  protect 25th %ile • 25th %ile > Nat Q  protect 7Q2

  18. flow components NRC 2005

  19. 2002 11 rivers 26 dams 13 states

  20. Savannah River Basin Richter et al 2006

  21. example flow prescription

  22. European Union • Water Framework Directive (2000) • Classify ecological status of water bodies • High, good, moderate, poor, bad • Measures to prevent deterioration and work toward at least a ‘good’ status • Each country legislates, implements

  23. South Africa • Timetable • 1994 – end of apartheid • 1996 – constitution signed • 1998 – National Water Act • Water reserve = ecology + basic human need • Phase I - ~20% of flow for ecology + 20 LPCD • Phase II – Building Block Methodology

  24. Australia • Driest inhabited continent; most dams/capita • Water Reform Framework (1994) • Sustainable use and protection of freshwater • Env Flow limit defined as point where additional change results in an increased risk of unacceptable degradation

  25. Murray-Darling Basin • Water cap (1997) • Capped to 1993/4 levels • Adjusted for climate • Allows for trading

  26. implementation • Adaptive management • “learn by doing” process • Water rights management • Procurement and retirement of existing consumptive-use permits via banking and trust systems • Dam removal • Dam reoperation

  27. questions for discussion How much water does a river need? Can this really be determined? How? What tools can be used to demonstrate the need for and value of environmental flows? What instruments can be used to implement environmental flow prescriptions?

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