Transcript Rivers for Life: Managing Water for People and Nature

Environmental Flows
Nature
for People and
© Insert Image Credit
© Mark Godfrey
Brian Richter, Director
Global Freshwater Program
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?
Establishment of links
between flow events,
channel hydraulics &
biophysical components
Lower
shrub
Upper
shrub/tree
Sedge
Moss
15
Wetbank
Water depth (m)
Aquatic
10
Inter-annual flood events
5
1:2 y 1:5 y
flood flood
wet-season low flow range
dry-season low flow range
0
0
50
100
Cross-channel distance (m)
150
Drybank
Environmental Flow Building Blocks
Savannah River, below Thurmond Dam (River-Floodplain)
Floods
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
Details:
20,000-40,000 cfs; 2-3 days, 1/month
Hypotheses:
• 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 events
of 2 week duration (March and early April)
High Flow
Pulses
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
<13,000 cfs; 3 successive years, every 10-20 years
• Floodplain tree recruitment
8,000-12,000 cfs;
• Exchange water with oxbows
>8,000 cfs
• Larval drift for pelagic spawners
Low Flows
<5,000 cfs
• Adequate floodplain drainage
• Create shallow water habitat for small-bodied fish
Key
Wet Year
Avg Year
Dry Year
3,000 cfs; 3 successive years every 10-20 years
• Floodplain tree recruitment
JAN
FEB
MAR
APR MAY
JUN
JUL
AUG
SEP
OCT NOV
DEC
E-Flow implementation:
Savannah River, Georgia
Ecosystem Monitoring & Adaptive Management
Ecological Limits of
Hydrologic Alteration
(ELOHA)
A framework for integrating
environmental flows into
regional water planning and
management
SCIENTIFIC PROCESS
Step 1. Hydrologic Foundation
Step 2. Stream Classification
Stream
Hydrologic
Classification
Baseline
Hydrographs
Hydrologic Model
and Stream Gauges
Step 3. Flow Alteration
Degree of
Hydrologic
Alteration
Developed
Hydrographs
Monitoring
Geomorphic
Stratification
Hydrologic
Alteration
by River Type
Step 4. Flow-Ecology Relationships
Flow - Ecology
Hypotheses
Ecological Data
and Indices
Flow Alteration-Ecological
Response Relationships
by River Type
SOCIAL PROCESS
Implementation
Adaptive Adjustments
Environmental
Flow Standards
Acceptable
Ecological Conditions
Societal
Values and
Management
Needs
M anaging W ater Flows
Sustainability Boundaries
Natural Flow or Lake
Fluctuations
Jan
Feb
M ar
Apr
M ay
Jun
Jul
Aug
Sep
Oct
N ov
D ec