Natural Flow Regime and Ecological Integrity of Rivers

Natural Flow Regime and
Ecological Integrity of Rivers
N. LeRoy Poff
Department of Biology &
Graduate Degree Program in Ecology
Colorado State University
Fort Collins, Colorado
Restauración de Rios Seminario International
Madrid 19.-21.9.06
In collaboration with:
Diego García de Jalón (Madrid);
María Alba Solans Verdu (Lleida)
Restoration
Science
“Reference”
Society
Condition
Degree of
Degradation
Current
Condition
Scientific
Understanding
- Tools
- Indicators of
Success
Desired
Future
Condition
Possible Goals:
• clean water
• uncontaminated food
• aesthetic appeal
• ecological
- rare species / diversity
- productive fishery
Political context
Action
From the European Union Water Framework
Directive (WFD), under “Surface water: Ecological
Protection”
(http://www.europa.eu.int/comm/environment/water/waterframework/overview.html):
“As no absolute standards for biological quality can
be set which apply across the Community, because
of ecological variability, the controls are specified
as allowing only a slight departure from the
biological community which would be expected in
conditions of minimal anthropogenic impact.”
From the European Union Water Framework
Directive (WFD), under “Surface water: Ecological
Protection”
(http://www.europa.eu.int/comm/environment/water/waterframework/overview.html):
“As no absolute standards for biological quality can
be set which apply across the Community, because
of ecological variability, the controls are specified
as allowing only a slight departure from the
biological community which would be expected in
conditions of minimal anthropogenic impact.”
From the European Union Water Framework
Directive (WFD), under “Surface water: Ecological
Protection”
(http://www.europa.eu.int/comm/environment/water/waterframework/overview.html):
“As no absolute standards for biological quality can
be set which apply across the Community, because
of ecological variability, the controls are specified
as allowing only a slight departure from the
biological community which would be expected in
conditions of minimal anthropogenic impact.”
“ … ecological protection should apply to all waters:
the central requirement of the Treaty is that the
environment be protected to a high level in its
entirety.”
From the European Union Water Framework
Directive (WFD), under “Surface water: Ecological
Protection”
(http://www.europa.eu.int/comm/environment/water/waterframework/overview.html):
“As no absolute standards for biological quality can
be set which apply across the Community, because
of ecological variability, the controls are specified
as allowing only a slight departure from the
biological community which would be expected in
conditions of minimal anthropogenic impact.”
“ … ecological protection should apply to all waters:
the central requirement of the Treaty is that the
environment be protected to a high level in its
entirety.”
What is the entirety?
… a self-sustaining ecosystem with natural
biodiversity and with the ability to respond
dynamically to future changes …
… restore fluvial processes
Ecological Processes
Ecosystem Function
(production)
Short-term
Goods & Services
Biotic Assemblage
(biodiversity)
Adaptive Capacity and
Long-term Sustainability
What does science tell us about
how rivers “function”?
Fundamental, general principle: River ecosystems
are naturally dynamic and “disturbance driven.”
River discharge (flow) is the prime generator of
natural variability and disturbance:
Floods and droughts are natural disturbances that
directly kill organisms and indirectly affect the amount
and quality of habitat for aquatic and riparian species.
Flow is the “maestro” that orchestrates much of
the complexity and heterogeneity at the core of
river ecosystems.
NOTE: Other factors also important (e.g., water quality)
Key role of Flow Regime
Poff et al. 1997. BioScience
Structure and function of river
ecosystem, and the adaptations
of its constituent species, are
dictated by the pattern of
temporal variation in river flows.
Rivers differ in their natural flow
regimes.
Key components of hydrologic variation:
magnitude
- frequency
- duration
- timing
- rate-of-change
-
Variation over many time scales
How does flow regime regulate ecological processes?
Bunn & Arthington. 2002.
Environmental Management
Just like every region has a climate, each river has a
natural flow regime, but rivers within the same region
may have different flow regimes due to other factors
that regulate rain-runoff processes:
•geology, soils,
•vegetative cover
•river size
Rivers vary in flow regimes in terms of …
magnitude,
frequency,
duration,
timing,
rate-of-change
At the scale of regions or countries, there is “diversity” in flow
regimes.
2 Distinctly Different Natural Flow Regimes
> 1 flood per year
Frequent dry periods
No seasonal timing
1 flood per year
No dry periods
High seasonal timing
Natural Flow Regimes in the U.S.
Poff & Ward (1990), Poff (1996).
Examples showing how aquatic and riparian
species react to natural flow regimes
Federally threatened floodplain wetland plant requires
flooding to suppress competitors and persist
Boltonia decurrens restricted to
open, wetland habitats in the
Illinois River floodplain.
Species produces many seeds
Populations declining
Flooding required for plant’s
success
- creates open, moist habitats
with lots of sunlight
Experiments show that without
flooding, competitor species
shade out native plant.
Cottonwood (Populus) gallery forests (western N.A.)
Require floodplain inundation at right time of year for
right amount of time
Flood timing regulates … production of fish (salmon)
in California mediterranean stream.
Natural winter floods:
- species of predator-resistant insect herbivore declines
- energy goes to herbivores that can be eaten by fish
Loss of winter floods (dams):
- “armored” insect species thrives
- energy cannot be transferred to fish
predatorresistant
herbivore
(after Wootton et al. 1996, Science)
(after Power et al 1990)
Natural Flow
Regimes in Spain
Example of 7 Rivers in Spain
Narcea
Aragón
Sorbe (Tajo)
Jarama (Tajo)
Cabriel
Guadalquivir
Grande
R Sorbe Muriel (71-79)
R. Sorbe Muriel (71-79)
3
3
2,5
2,5
Qmonth/Qannual
2
2
1,5
1,5
1
1
0,5
0,5
CV
0
0
OCT NOV DES JAN FEB MAR APR MAI
JUN
R. Jarama Algete (40-71)
Sorbe (Tajo)
R. Jarama Algete (40-71)
3
2,5
Qmonth/ Qannual
2
1,5
1
0,5
0
OCT NOV DEC JAN FEB MAR APR MAI
OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP
JUL AUG SEP
JUN
JUL
2
1,8
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
CV
OCT NOV DEC JAN FEB MAR APR MAI JUN
AUG SEP
JUL AUG SEP
R. Guadalquivir Sta. Maria (43-88)
R. Guadalquivir Sta. Maria (43-88)
3,0
2
1,8
2,5
1,6
Qmonth/Qannual
2,0
CV
1,4
1,2
1
1,5
0,8
1,0
0,6
0,4
0,5
0,2
0
0,0
OCT
NOV
DES
JAN
FEB
MAR
APR
MAI
JUN
JUL
AUG
SEP
OCT
NOV
DES
JAN
FEB
MAR APR
MAI
JUN
JUL
AUG
SEP
Guadalquivir
Jarama (Tajo)
R Sorbe Muriel (71-79)
R. Sorbe Muriel (71-79)
3
3
2,5
2,5
Qmonth/Qannual
2
2
1,5
1,5
1
1
CV
Sorbe (Tajo)
0,5
0,5
0
0
OCT NOV DES JAN
FEB MAR APR MAI
JUN
JUL
OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP
AUG SEP
Jarama (Tajo)
R. Jarama Algete (40-71)
R. Jarama Algete (40-71)
3
2,5
Qmonth/ Qannual
2
1,5
1
0,5
0
OCT NOV
DEC
JAN
FEB
MAR APR
MAI
JUN
JUL
2
1,8
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
CV
OCT NOV DEC JAN
AUG SEP
FEB MAR APR
MAI
JUN
JUL AUG SEP
Cabriel
R. Cabriel 112 (56-72)
R. Cabriel 112 (56-72)
R. Guadalquivir Sta. Maria (43-88)
R. Guadalquivir Sta. Maria (43-88)
3,0
2
3,0
1,8
2,5
2
1,6
Qmonth/Qannual
2,0
1,8
CV
1,4
2,5
1,2
Qmonth/ Qannual
1
1,5
0,8
1,0
0,6
1,4
1,5
1,2
1
0,4
0,5
0,2
0
0,0
OCT
NOV
DES
JAN
FEB
MAR
APR
MAI
JUN
JUL
AUG
SEP
OCT
NOV
DES
JAN
FEB
MAR
APR
MAI
JUN
JUL
AUG
SEP
CV
0,8
1,0
Guadalquivir
1,6
2,0
0,6
0,4
0,5
Grande
0,2
0
0,0
OCT NOV DES
JAN
FEB MAR APR MAY JUN
JUL
AUG SEP
OCT NOV DES JAN FEB MAR APR MAY JUN JUL AUG SEP
R. Grande Coin (80-99)
R. Grande Coin (80-99)
2
2,5
1,8
1,6
2
Qmonth/ Qannual
CV
1,4
1,5
1,2
1
0,8
1
0,6
0,5
0,4
0,2
0
0
OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP
OCT NOV DEC JAN FEB MAR APR MAI JUN
JUL AUG SEP
R. Narcea Cangas (66-81)
R. Narcea Cangas (66-81)
2
3
1,8
2,5
1,6
Qmonth/ Qannual
1,4
2
CV
1,2
1
1,5
0,8
1
Narcea
0,6
0,4
0,5
0,2
0
0
OCT NOV DEC JAN FEB MAR APR MAI JUN
OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP
JUL AUG SEP
Aragón
R. Aragon Yesa (14-60)
R. Aragon Yesa (14-60)
3
2
1,8
1,6
1,4
1,2
Qmonth/ Qannual
2,5
2
1,5
1
R Sorbe Muriel (71-79)
R. Sorbe Muriel (71-79)
3
3
2,5
0,5
2,5
Qmonth/Qannual
2
2
1,5
1,5
1
1
0,5
0,5
0
0
OCT NOV DES JAN
FEB MAR APR MAI
JUN
JUL
CV
0
OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP
OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP
AUG SEP
CV
1
0,8
0,6
0,4
0,2
0
OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP
Sorbe (Tajo)
Jarama (Tajo)
R. Jarama Algete (40-71)
R. Jarama Algete (40-71)
3
2,5
Qmonth/ Qannual
2
1,5
1
0,5
0
OCT NOV
DEC
JAN
FEB
MAR APR
MAI
JUN
JUL
2
1,8
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
CV
OCT NOV DEC JAN
AUG SEP
FEB MAR APR
MAI
JUN
JUL AUG SEP
Cabriel
R. Guadalquivir Sta. Maria (43-88)
R. Guadalquivir Sta. Maria (43-88)
R. Cabriel 112 (56-72)
R. Cabriel 112 (56-72)
3,0
2
1,8
2,5
3,0
2
1,6
Qmonth/Qannual
2,0
1,8
2,5
CV
1,4
1,6
Qm onth/ Qannual
2,0
1,4
0,8
1,5
1,2
1
0,6
1,0
1,2
1
1,5
1,0
0,6
0,2
0
OCT
NOV
DES
JAN
FEB
MAR
APR
MAI
JUN
JUL
AUG
SEP
0,4
0,5
0,2
0,0
CV
0,8
0,4
0,5
0,0
OCT
NOV
DES
JAN
FEB
MAR
APR
MAI
JUN
JUL
AUG
SEP
Guadalquivir
0
OCT
NOV
DES
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT NOV DES
Grande
R. Grande Coin (80-99)
R. Grande Coin (80-99)
2
2,5
1,8
1,6
2
Qmonth/ Qannual
CV
1,4
1,5
1,2
1
0,8
1
0,6
0,5
0,4
0,2
0
0
OCT NOV DEC JAN
FEB MAR APR
MAI
JUN
JUL
AUG SEP
OCT NOV
DEC
JAN
FEB
MAR APR
MAI
JUN
JUL
AUG SEP
JAN
FEB MAR APR MAY JUN
JUL
AUG SEP
What happens when natural flow regimes
are altered?
Sources of flow alteration
- Land Use Change
- Agricultural conversion
- Urbanization
- Water Schemes
- Diversions
- Groundwater pumping
- Dams
Consequences of Flow Alteration?
Local Effects:
- downstream habitat
- downstream temperature
- biotic interactions
- floodplain isolation, etc.
Landscape Effects:
- fragmentation of networks
- regional homogenization
- land-ocean processes
Ecological Processes
Ecosystem Function
(production)
Short-term
Goods & Services
Biotic Assemblage
(biodiversity)
Adaptive Capacity and
Long-term Sustainability
Recent Literature Review of
Ecological Responses to Flow Alteration
(NL Poff and D. Pepin, unpublished)
• >100 published papers (and growing)
• Characterized by:
– Type of flow alteration
– Ecological response
• Diversity/Ecosystem function
• Flora/fauna
• Channel/floodplain
– Geographic distribution
M
ac
ro
in
ga
M
ac
r
an
ib
s
ns
rd
ia
Bi
s
s
ph
h
p
o
e
yt
Am
ri
or
pa
e
Ri
te
es
ra
sh
eb
Fi
rt
0
Al
ve
Number of Studies
Ecological Responses
40
35
30
25
20
15
10
5
Magnitude of Flow
55%
Within-channel responses:
•Life cycle disruption
Number of Studies
28
•Loss of sensitive species
24
•Reduced diversity
20
•Wash-out and/or stranding
16
•Reduced densities of
aquatic organisms
12
•Altered energy flow
8
•Invasion or establishment of
exotics
4
0
Increased
variation
Flow
stabilization
Magnitude of Flow
Riparian responses:
55%
• Invasion/establishment of
exotics
Number of Studies
14
• Reduction /elimination of
recruitment
12
10
• Encroachment of vegetation
into channels
8
6
4
2
0
Increased
variation
Flow
stabilization
16%
Timing of Flow
Number of Studies
12
•Disrupt life cycle cues
10
• Reduced aquatic and
riparian community diversity
8
• Invasion/establishment of
exotics
6
4
2
0
Shift in
Seasonality
of peak
Decreased
predictability
Increased
predictability
Literature Review Reveals
• Further confirmation that flow alteration has
dramatic ecological effects
– Reduced species diversity in response to many
altered flow components
– Shift in community dominants
– Establishment of non-native species
– Effects on ecosystem function not well-studied
• Flow alteration alone is important
Reviews of Ecological Responses
to Flow Regime Alteration
Poff et al. 1997. BioScience
Bunn & Arthington. 2002.
Environmental Management
Lytle & Poff 2004. Trends in
Ecology & Evolution.
Spanish Dams and Flow Regimes
Narcea
Arroyo
Aragón
Najerilla
Sorbe (Tajo)
Jarama (Tajo)
Cabriel
Júcar
Guadalquivir
Grande
Effects of Dams
• Daily hydrograph
• Monthly hydrograph
Arroyo (Ebro) 1917-1944
Arroyo (Ebro) 1917-1944
2
30
1,8
1,6
1,4
20
1,2
CV
Q (m3/s)
Before
25
15
1
0,8
10
0,6
0,4
5
0,2
0
0
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Arroyo (Ebro) 1945-2001
Arroyo (Ebro) 1945-2001
30
2
25
1,8
1,6
1,4
1,2
15
CV
Q (m3/s)
After
20
1
0,8
10
0,6
0,4
5
0,2
0
0
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Winter floods
Summer low flows
Summer floods
Winter floods
Summer low flows
Summer floods
-Spanish Dams
reverse normal seasonal signals of high
flows and low flows
“homogenize” regional differences in
natural flow regimes
R. Narcea Cangas (66-81)
3
2,5
Narcea
Qmonth/ Qannual
2
1,5
1
0,5
0
OCT NOV DEC JAN
FEB MAR APR MAI
JUN
JUL
AUG SEP
Aragón
R. Aragon Yesa (14-60)
3
Qmonth/ Qannual
2,5
2
1,5
R. Sorbe Muriel (71-79)
1
3
0,5
2,5
0
Qmonth/Qannual
OCT NOV DEC JAN FEB MAR APR MAI JUN
2
JUL AUG SEP
1,5
1
0,5
0
OCT NOV DES JAN FEB MAR APR MAI JUN
JUL AUG SEP
Sorbe (Tajo)
Jarama (Tajo)
R. Jarama Algete (40-71)
3
2,5
Qmonth/ Qannual
2
1,5
1
0,5
0
OCT NOV DEC JAN FEB MAR APR MAI JUN
JUL
AUG SEP
Cabriel
R. Cabriel 112 (56-72)
R. Guadalquivir Sta. Maria (43-88)
3,0
3,0
2,5
2,5
Qmonth/ Qannual
2,0
Qmonth/Qannual
2,0
1,5
1,5
1,0
1,0
0,5
0,5
0,0
0,0
OCT NOV DES
JAN
FEB
MAR APR
MAI
JUN
JUL
AUG
OCT NOV DES
SEP
Guadalquivir
Grande
R. Grande Coin (80-99)
2,5
2
Qmonth/ Qannual
1,5
1
0,5
0
OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP
JAN
FEB MAR APR MAY JUN
JUL
AUG SEP
Options for restoration?
•Dam removal
Recent history in U.S. - mostly small
•Manage dams to restore components of
natural flow regime through “adaptive
management” (Stanford et al. 1996, Poff
et al. 2003)
Natural
Regulated
Re-regulated
Next Steps?
Characterize Natural
Flow Regime
Determine Degree of
Hydrologic Alteration
Restoration
Science
Society
Condition
Degree of
Degradation
Current
Condition
???
Prescribe Flow Regime for
Restoration; Monitor
Ecological Responses
“Reference”
Scientific
Understanding
- Tools
- Indicators of
Success
Desired
Future
Condition
Possible Goals:
• clean water
• uncontaminated food
• aesthetic appeal
• ecological
- rare species /
diversity
- productive fishery
Political context
Action
Conduct National Survey to determine “types” of
natural flow regimes across Spain.
Use “types” to assist goal planning for restoration
planning on national scale.
Thank you for your attention
Special thanks to:
Marta González del Tánago;
Ministerio de Medio Ambienta