1. Anthropogenic fragmentation severely limits movement
Very large dams globally
(B. Lehner, WWF)
"GWSP Digital Water Atlas (2008). Map 25: River Fragmentation by Dams (V1.0). Available online at
Global fragmentation of large river basins
Snake River dams and decline of Chinook salmon
Dams on the Columbia River
>75,000 dams 2+m high in U.S.

2. Streamflow regime: a “master” variable
Varies over time
- Day to day, week to week, year to year
- Inter-annual variation of wet and dry years
Varies along a river’s length
Varies regionally with climate
(Poff et al., 1997)

3. Streams and rivers differ in natural flow regimes
Key components that characterize a full flow regime and that have ecological importance:
Magnitude of discharge – amount
Frequency of events
Duration
Timing - regularity and seasonal predictability
Rate of change

4. Streams and rivers differ in natural flow regimes

5. Hydrogeography of natural flow regimes in U.S.
Offers context for considering regional variation in impacts of climate change on pattern of natural (background) variation
Poff & Ward (1989, 1990), Poff (1996).

6. Key science challenges?
Develop a better scientific understanding of geographically-distributed risk to FW species and ecosystems (research issue)
Develop science-based conservation “priorities” based on regional risk and likelihood of successful interventions
Develop models that capture fine scale hydro-geomorphic and ecological grain (river segment scale?) and in a river network context. Different from terrestrial systems in this regard!
Develop better methods for “quantifying” ecosystem goods and services and the long-term ecological costs and benefits of different management options
New paradigm for water management that proactively accommodates ecosystem needs at local to regional scales in order to build ecological resilience in the face of rapid climate change.

7. Natural flow regime and ecological processes
Specifics of magnitude, frequency, duration, timing and rate-of-change dictate ecological processes and outcomes.
Bunn & Arthington Environmental Management

8. General philosophy of restoring flow-altered systems
Quantify changes in disturbance/flow regime
Before vs. After
Indicators of Hydrologic Alteration (Richter et al. 1996; Mathews & Richter 2007)
Many other metrics (Olden & Poff 2003)
Natural
Regulated
Re-regulated
Aim to restore (re-regulate) components of natural flow regime that provide key ecological functions
Stanford et al., 1996, The normative river concept, Regulated Rivers.

9. International Concern and Consensus

10. Freshwater biodiversity is at disproportionate risk of extinction
Vulnerable and Imperiled Species
Projected extinction rates
Freshwaters:
3.7% per decade
Terrestrial vertebrates:
0.8% per decade
(Ricciardi & Rasmussen 1999)
(L. Master, TNC)

11. Ecosystem Goods, Services, Amenities
(Poff et al. 2002)

12. What are the major threats to FW Ecosystems?
Many interacting factors contribute to global biodiversity crisis and FW ecosystem degradation.
Over-
Exploitation
Water
Pollution
Habitat
Degradation
Species
Invasions
Flow
Modification
Fig. 1. The five major threat categories and their established
or potential interactive impacts on freshwater biodiversity.
Climate change will exacerbate these continuing threats.
(Dudgeon et al. 2006)

13. Extensive wetland draining in United States since the 1800s.
Current human management practices have altered ecosystem goods and services
Extensive wetland draining in United States since the 1800s.
Extensive fragmentation by
>75,000 dams 2+ m high in U.S.

14. A key point: Is this possible during climate change?
Functional, self-sustaining ecosystems are needed to provide ecosystem goods & services and to maintain native biodiversity.
Is this possible during climate change?
Need to know how FW ecosystems function and how sensitive function is to climate change

15. Pressing Conservation Issue
Define the water needs of freshwater ecosystems to legitimize their protection and restoration.
(Baron, Poff et al., 2002, Ecol. Appl.)
(Poff et al., 2003, Frontiers Ecol. Environ.)
Key Question: How do we develop guidelines for flow needs in unstudied streams?

16. Scientific approach of ELOHA
- Classify streams in a region according to natural flow regimes (and subclassify according to major geomorphic setting).
- Define natural range of hydrologic variation and ecological variation for each stream class.
- Put flow-impaired streams into one of the natural flow regime classes.
- Establish ecological responses to flow alteration for each class.
- Test with existing field data or monitoring data.
- Refine models.
- Continue…
Arthington et al., 2006, Ecol. Appl.
Complete presentation available at:
Poff publications referenced in lecture are at:

17. A framework for developing regional environmental flow standards
The Ecological Limits of Hydrologic Alteration (ELOHA)
A framework for developing regional environmental flow standards
LeRoy Poff, CSU
Brian Richter, TNC
Angela Arthington, ARI (Australia)
Stuart Bunn, ARI (Australia)
Robert Naiman, UW
Eloise Kendy, TNC
Mike Acreman, CEH (UK)
Colin Apse, TNC
Brian Bledsoe, CSU
Mary Freeman, USGS
James Henriksen, USGS
Robert Jacobson, USGS
Jonathan Kennen, USGS
David Merritt, USFS
Jay O’Keeffe, UNESCO-IHE (Netherlands)
Julian Olden, UW
Kevin Rogers, U. Witwatersrand (SA)
Rebecca Tharme, IWMI (Sri Lanka)
Andrew Warner, TNC

19. SCIENTIFIC PROCESS SOCIAL PROCESS Step 1. Hydrologic Foundation
Monitoring
Acceptable
Ecological Conditions
Societal
Values and Management Needs
Implementation
SOCIAL PROCESS
Adaptive Adjustments
Flow Alteration-Ecological
Response Relationships
by River Type
Stream Hydrologic
Classification
Degree of Hydrologic
Alteration
Hydrologic Alteration
Baseline
Hydrographs
Developed
Ecological Data
and Indices
Environmental
Flow Standards
Hydrologic Model
and Stream Gauges
Flow - Ecology
Hypotheses
Geomorphic Stratification
Step 4. Flow-Ecology Relationships
Step 3. Flow Alteration
Step 2. Stream Classification

20. Pressing Conservation Issue
Define the water needs of freshwater ecosystems to legitimize their protection and restoration.
(Baron, Poff et al., 2002, Ecol. Appl.)
(Poff et al., 2003, Frontiers Ecol. Environ.)
Key Question: How do we develop guidelines for flow needs in unstudied streams?

21. Scientific approach of ELOHA
- Classify streams in a region according to natural flow regimes (and subclassify according to major geomorphic setting).
- Define natural range of hydrologic variation and ecological variation for each stream class.
- Put flow-impaired streams into one of the natural flow regime classes.
- Establish ecological responses to flow alteration for each class.
- Test with existing field data or monitoring data.
- Refine models.
- Continue…
Arthington et al., 2006, Ecol. Appl.
Complete presentation available at:
Poff publications referenced in lecture are at: