© 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