An Introduction to Environmental Flows

Transcription

1 An Introduction to Environmental Flows The natural flow regime Flow alteration Environmental flows defined Scaling up Eloise Kendy, Ph.D. IUCN workshop Kathmandu, Nepal 5 August 2011 Jefferson River, Montana Eloise Kendy, photo

2 Ch S B

3 Status of freshwater species Proportion of U.S. Species at Risk The most threatened species are all in freshwater

4 Key Factors Affecting Aquatic Ecosystems

5 Flow is the Master Variable Flow Regime (low flows, high pulses, floods) Physical Habitat Water Quality Connectivity Energy Supply Species Interactions Ecological Integrity Ecosystem Services

6 Flow is the master variable.

7 The Natural Flow Paradigm The full range of natural intra- and inter-annual variation in hydrologic regimes, and associated characteristics of timing, duration, frequency, and rate of change, are critical in sustaining the full native biodiversity and integrity of aquatic ecosystems. (Poff et al. 1997)

8 Hydrological Alteration: Any anthropogenic disruption to the magnitude or timing of natural river flows (Rosenberg et al. 2000) Flow regulation Loss of river-floodplain connectivity

9 What alters hydrology? Dams Withdrawals Land-Use Change Climate Change

10 The History of Global Dam Development

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12 Proliferation of Future Dams Percentage of economically feasible hydropower potential that has been developed (International Hydropower Association)

13 Dams Disconnect river reaches, preventing migration Pond water in reservoirs upstream Alter flow patterns downstream for: Water supply Hydropower production Recreation Flood control Downstream impacts: Sediment Water quality Temperature Flow

14 Impacts of reservoir operation for flood control, Yangtze River Intermediate Flow Year, With Flood Pool Summer Target 6000 m 3 /s Natural Daily Inflow Outflow Too cold and too early for fish spawning m 3 /s Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

15 diversion irrigation industry Withdrawals municipal drinking and sanitation

16 Global Water Consumption

17 Source: World Commission on Water in the 21 st Century Global Water Stress

18 Ground-water discharge creates wetlands and contributes to surface flows. Carter 1996 (USGS WSP 2425)

19 Effects of ground-water pumping Pre-pumping Well 1 Well 2 Alley et al, 1999, USGS Circular 1186, fig. 13

20 Streamflow depletion: The inevitable consequence of ground-water withdrawal. CHINA Fuyang Basin, North China Plain (Kendy, 2002) See also: WATER FOLLIES by R. Glennon

21 Land-Use Change Ground-water flow paths Winter et al, USGS Circular 1139, fig. 3

22 Climate Change MORE FREQUENT DROUGHTS MORE FREQUENT FLOODS HIGHER TEMPERATURES EARLIER SNOWMELT Eloise Kendy, photos

23 What are environmental flows?..vs. minimum flows?..vs. instream flows? The Brisbane Declaration

24 Environmental Flow: Pattern of water flows through a natural river or lake that sustains healthy ecosystems and the goods and services that humans derive from them.

25 Source: Mike Roberts, Montana DNRC Not just minimum flows. Flow requirements for endangered arctic grayling Big Hole River at Wisdom, Montana (USA) 2008 USGS flow data is provisional Spawning Fry emergence Fry / juvenile rearing, adult summer habitat flow at Wisdom, cfs Adults migrating to winter habitat 400 0

26 Not just fish.

27 Not just instream flows. Savannah River, GA

28 Out-of-stream environmental flows in Australia Murray-Darling, Australia: diversions from instream flows to floodplain to restore flood-dependent gum tree forests Progressive deterioration of a red gum tree, Murray River, Australia

29 ENVIRONMENTAL FLOW COMPONENTS Streamflow (cfs) High flow pulse Large flood Low flow Small flood Output from TNC s IHA software Extreme low flow For each: Day of Year What are some ecological functions?

30 Environmental flow prescription Postel and Richter, 2003

31 Natural (undepleted & unregulated) Flow Flood Flow Criteria: -40% < Q < +10% River Flow E-Flow Criteria Low Flow Criteria: -20% < Q < +20% High Flow Criteria: -30% < Q < +10% Day of Year Sustainability boundaries Richter, 2010

32 Implementing Environmental Flow Recommendations (Discussion) Dams Withdrawals Land Use Climate Change

33 Scaling up: from dams to basins

34 Mitigation at scale of a dam Can potentially address: Seasonal patterns of flow and flow events Impacts from peaking operations However, may be limited by operational constraints. More difficult to address: Migratory fish and longitudinal connectivity Sediment Temperature and water quality Loss of free-flowing river

35 Limits to sustainability at scale of dam Spawning habitat Floodplain fishery

36 System-scale design principles Mitigation Hierarchy 1. Avoid 2. Minimize 3. Offset $ $ Spawning habitat Environmental Flows Pump-back energy storage Floodplain fishery

37 Penobscot River Restoration Energy Medway Dam (expanded) Piscataquis River Howland Penobscot River Fisheries West Enfield Dam Existing Fish Passage West Enfield Dam Howland Dam Decommission / Innovative Fish Bypass Penobscot River Milford Dam Stillwater Dam (expanded) Orono Dam (added) Indian Island Stillwater River Old Town Orono Milford Dam New Upstream Fish Passage Great Works Dam Decommission / Removal Veazie Dam Decommission / Removal 0 Ellsworth Dam (Union River) Bangor Penobscot River

38 Existing Conditions Veazie Dam MMI Engineering

39 Projected Conditions Veazie Dam MMI Engineering

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41 Penobscot example: system planning Scenario A (the past) Scenario B (the future) Annual energy generation Proportion of basin accessible to migratory fish Annual shad run ~ 300,000 MWh Minimal Near zero

42 Penobscot example: system planning Scenario A (the past) Scenario B (the future) Annual energy generation ~ 300,000 MWh ~ 300,000 MWh Proportion of basin Minimal Majority of basin accessible to migratory fish Annual shad run Near zero 1.5 million If system planning had occurred in the Penobscot in 1880, which scenario would they have chosen?

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