Post on 15-Dec-2015
© Mark Godfrey
Brian Richter, DirectorGlobal Freshwater Program
© Insert Image Credit
Environmental Flows for People and Nature
From “Rivers for Life: Managing Water for People and Nature” by Sandra Postel and Brian Richter, Island Press
This is the same volume!
Definition of Environmental Flows
“Environmental flows” describe 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.
Source: The Brisbane Declaration, International RiverSymposium, September 2007
Maintaining Natural Flow Patterns
From “Rivers for Life: Managing Water for People and Nature” by Sandra Postel and Brian Richter, Island Press (adapted from Tharme and King 1998)
The Big Question
How much flow alteration (e.g., from dam operations and water
withdrawals) is too much?
0 50 100 150
0
5
10
15
wet-season low flow rangedry-season low flow range
Wate
r d
ep
th (
m)
Cross-channel distance (m)
1:2 yflood
1:5 yflood
Establishment of Establishment of links between flow links between flow events, channel events, channel hydraulics & hydraulics & biophysical biophysical componentscomponents
Aquatic
Wetbank Drybank
Sedge
Moss
Lower shrub
Upper shrub/tree
Inter-annual flood events
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Environmental Flow Building BlocksSavannah River, below Thurmond Dam (River-Floodplain)
Low Flows
High FlowPulses
Floods
3,000 cfs; 3 successive years every 10-20 years• Floodplain tree recruitment
<5,000 cfs• Adequate floodplain drainage
• Create shallow water habitat for small-bodied fish
>8,000 cfs• Larval drift for pelagic spawners
50,000-70,000 cfs; 2 weeks, avg every 2 yrs• Maintain channel habitats
• Create floodplain topographic relief• Provide fish access to the floodplain
• control invasive species• Maintain wetlands and fill oxbows and sloughs
• Enhance nutrient cycling & improve water clarity• Disperse tree seeds
<13,000 cfs; 3 successive years, every 10-20 years• Floodplain tree recruitment
8,000-12,000 cfs;• Exchange water with oxbows
20,000-40,000 cfs; 2-3 days, 1/month• Provide predator-free habitat for birds
• Disperse tree seeds• Transport fish larvae
• Flush woody debris from floodplain to channel• Floodplain access for fish
• Fish passage past navigation dam
>30,000 cfs;5 pulses, >2 days with 2 eventsof 2 week duration (March and early April)
Key
Dry Year
Avg Year
Wet Year
Details:20,000-40,000 cfs; 2-3 days, 1/monthHypotheses:• Provide predator-free habitat for birds• Disperse tree seeds• Transport fish larvae• Flush woody debris from floodplain to channel• Floodplain access for fish• Fish passage past navigation dam
E-Flow implementation:Savannah River, Georgia
Ecosystem Monitoring & Adaptive Management
A framework for integrating environmental flows into
regional water planning and management
Ecological Limits of
Hydrologic Alteration
(ELOHA)
Step 1. Hydrologic Foundation
SCIENTIFIC PROCESS
Monitoring
AcceptableEcological Conditions
SocietalValues and
Management Needs
Implementation
SOCIAL PROCESS
Adaptive Adjustments
Flow Alteration-Ecological Response Relationships
by River Type
Stream Hydrologic
Classification
Degree of HydrologicAlteration
Hydrologic Alteration
by River Type
BaselineHydrographs
DevelopedHydrographs
Ecological Data and Indices
Environmental Flow Standards
Hydrologic Modeland Stream Gauges
Flow - EcologyHypotheses
Geomorphic Stratification
Step 4. Flow-Ecology Relationships
Step 3. Flow Alteration
Step 2. Stream Classification
Managing Water Flows
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Natural Flow or Lake Fluctuations
Sustainability Boundaries