Environmental Flows

1. Environmental Flows Eric S. Hersh CE397 November 10, 2005 (National Geographic)

2. (USFWS, 2005)

3. (CSIRO, 2003)

4. (M.Bogan, Oregon State U)

5. topical development dams and reoperation Elaine, Andrew environmental flows (science) Eric, Becky water reserve (policy) Shane, Tyler

6. environmental flow definition • Water left in or released into a river system, often for managing some aspect of its conditions • Endangered species protection • Healthy ecosystem • Sediment transport • Commercial fisheries yield • Freshwater inflows to bays and estuaries • Waste assimilation

7. environmental flow requirements • Flows to sustain or restore the ecological functions (goods and services) of a river • Fish and wildlife: habitat, migration, reproduction, biodiversity • Recreation • Navigation • Hydropower • Waste assimilation • Water supply • Food supply • Flood and drought mitigation • Nutrient delivery • Coastal salinity regulation

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

9. international 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

10. human impact (USBR, 2004)

11. 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.”

12. 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, etc

13. Question: manage flow for…?

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

15. the natural flow regime • Magnitude • Frequency • Duration • Timing • Rate of change of hydrologic events

16. characterizing streamflow Maidment et al 2005 • Subsistence flow • Water quality (temperature, DO, waste assimilation) • Riparian plant recruitment • Purge invasive species • Base flow • Dominant flow condition in many rivers • Determines available habitat

17. characterizing streamflow Maidment et al 2005 • Flow pulses • Within banks • Macrophyte growth/SOD control • Nutrient and organic matter delivery • Shape the river channel geometry • Longitudinal connectivity • Flood flows • Overbank • Lateral connectivity • Riparian plant germination • “Food bazaar”

18. human impact • Artificial higher or lower low flows • Erratic daily flows from hydropower demand • Prevent or minimize floods • Disconnect floodplain • Channelize rivers and alter lotic habitat • Erase life cycle flow cues • Eliminate variability

19. human impact (Postel and Richter, 2003)

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

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

22. quantifying environmental flows • 1950s-present • South Africa, Australia, United States • Hydrologic (Desktop) Models • Hydraulic Models • Habitat Models • Holistic Models

23. quantifying environmental flows • Hydrologic (Desktop) Models • Simple, cheap, easy • Use flow as an indicator for ecological and biological functions • Examples: • Indicators of Hydrologic Alteration (IHA), The Nature Conservancy, 1997 • Tennant Method (a.k.a. Montana Method), U.S. Fish and Wildlife Service, 1976 • Lyons Method, Texas Parks and Wildlife Dept., 1979.

24. quantifying environmental flows • Hydraulic Models • Correlate flow with available habitat area based on river channel geometry • Physical proxy for in-stream ecology and biology • Examples: • Wetted Perimeter Method, Montana Dept. of Fish, Wildlife, and Parks, 1970s • R2-Cross Method, Colorado Div. of Wildlife, 1980s

25. quantifying environmental flows • Habitat Models • Complex, data intensive • Use target species population data with hydraulic data to determine optimal habitat • Examples: • Instream Flow Incremental Methodology (IFIM), U.S. FWS, 1970s. Includes Physical Habitat Simulation Model (PHABSIM). Mainly used for economically valuable or endangered species; legal credibility.

26. quantifying environmental flows • Holistic Models • Very complex, resource and data intensive • Comprehensive ecosystem assessment • Examples: • Building Block Methodology (BBM), South Africa Dept. of Water Affairs and Forestry and Univ. of Cape Town, 1990s. Top-down approach. • Downstream Response to Imposed Flow Transformation (DRIFT), above plus Southern Waters Ecological Research and Consulting, 1990s

27. issues in quantifying environmental flows • Scaling • Ecological indicators • Integration • Data and resource availability • Legal/regulatory status

28. natural flow regime restoration (Postel and Richter, 2003)

29. implementation • Dam reoperation • Dam removal • Controlled floods • Adaptive management (Postel and Richter, 2003)

30. dam removal (GZA GeoEnvironmental, 2000) Old Berkshire Mill Dam E. Branch Housatonic River, Massachusetts

31. dam removal Livermore Pond Dam Easton, Connecticut (E.Hersh, 2003)

32. dam removal Livermore Pond Dam Easton, Connecticut

33. 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?