ecological implications of erratic floods in large river ... · the flood pulse concept (junk et...
TRANSCRIPT
Ecological Implications of Erratic
Floods in Large River Floodplains of
the Andean Amazon Region
Jorge E. Celi & Stephen K. Hamilton Department of Zoology & Kellogg Biological Station
Michigan State University [email protected]
The Flood Pulse Concept (Junk et al. 1989)
• Floodplains are transitional between
aquatic and terrestrial zones.
• Large unmodified watersheds
produce flood pulses of long
duration and extensive seasonal
floodplain inundation.
• Small or modified systems produce
frequent flood pulses of shorter
duration.
• Predictable pulses allow organisms
to adapt to and benefit from
inundation.
• Unpredictable pulses act as a
disturbance and impede adaptation.
Poff et al. 1997. The
Natural Flow Regime.
Naiman et al. 2008. Flow
variability and the biophysical
vitality of river systems.
The Natural Flow
Regime concept
can be extended
to Flood Regimes
on floodplains
The Napo River
• Drains 105 km2 of a highly
diverse and largely undisturbed
region of the western Amazon
in Ecuador and Peru.
• Fringed with extensive
floodplains along 800 km of
lowland reaches.
• Exceptional levels of
biodiversity may be related to
flood regimes.
• Intermediate disturbance
hypothesis
100 Km
upstream
reaches
downstream
reaches
Andes
Amazon
Laraque et al. 2009. Hydrol. Proc.
middle
reaches
Source: INAMHI-SENAMHI, Hybam Project.
• Highly variable and less
predictable flow and flood
regimes (multiple short
pulses).
• Contrasts with more
predictable, mono-modal
regimes of the Amazon,
Orinoco, Parana rivers.
• Stage fluctuations range
from 4 m in upper reaches
to 9 m in lower reaches, vs.
16 m in the central Amazon.
Water levels of the
Napo River
Source: ANA, Brazil.
0
1
2
3
4
5
6
Ma
r-0
1
Oct-
01
Ma
y-0
2
Dec-0
2
Ju
l-0
3
Feb
-04
Se
p-0
4
Ap
r-0
5
Nov-0
5
Ju
n-0
6
Ja
n-0
7
Au
g-0
7
Ma
r-0
8
Oct-
08
Ma
y-0
9
Dec-0
9
Ju
l-1
0
Feb
-11
wa
ter
leve
l (m
)
upstream Napo - Ecuador
0
5
10
15
20
25
Ja
n-0
1
Au
g-0
1
Ma
r-0
2
Oct-
02
Ma
y-0
3
Dec-0
3
Ju
l-0
4
Fe
b-0
5
Se
p-0
5
Ap
r-0
6
Nov-0
6
Ju
n-0
7
Ja
n-0
8
Au
g-0
8
Ma
r-0
9
Oct-
09
Ma
y-1
0
Dec-1
0
Ju
l-11
wa
ter
leve
l (c
m)
Amazon- Brazil
0
4
8
12
16
20
0
100
200
300
400
500
600
jan
feb
ma
r
ap
r
ma
y
jun
jul
au
g
se
p
oct
no
v
de
c
Wa
ter
leve
l (m
)
pre
cip
ita
tio
n (
mm
)
Central Amazon - Brazil
AVG PP (mm) AVG WL (m)
Source: INAMHI-SENAMHI, Hybam Project.
• Less pronounced seasonality
in the Napo.
• Hydrograph coupled to
precipitation events towards
the upper reaches and
decoupled (like the Amazon)
towards the lower reaches.
Water levels and
precipitation
Source: ANA, Brazil. 0
2
4
6
8
0
100
200
300
400
jan
feb
ma
r
ap
r
ma
y
jun
jul
au
g
se
p
oct
no
v
de
c
Wa
ter
leve
l (m
)
Pre
cip
ita
tio
n (
mm
)
downstream Napo- Peru
AVG PP (mm) AVG WL (m)
0
1
2
3
4
0
100
200
300
400
jan
feb
ma
r
ap
r
ma
y
jun
jul
au
g
se
p
oct
no
v
de
c
Wa
ter
leve
l (m
)
Pre
cip
ita
tio
n (
mm
)
upstream Napo - Ecuador
AVG PP(mm) AVG WL (m)
Magnitude: Depth of inundation
0
2
4
6
8
10
jan
feb
ma
r
ap
r
ma
y
jun
jul
au
g
se
p
oct
no
v
de
c
wa
ter
leve
l (m
)
River levels
upstream Napo
downstream Napo central Amazon
• Napo River has smaller
amplitude of water levels
than the Central Amazon.
• Lower depth of
flooding.
• Deepest flooding occurs at
floodplain sites proximal to
river.
• Floodplain biota less
adapted to cope with
deeper floods? 0
100
200
300
0 100 200 300
ma
x d
ep
th (
cm
)
# days flooded
Inundation hydrology of the Napo floodplains
distal forested swamp
proximal forested swamp
Duration: Floodplain Hydroperiod
0
10
20
30
40
50
100 200 300 400
me
dia
n d
ep
th (
cm
)
days flooded per year
Napo proximal floodplain
- high connectivity
Napo proximal floodplain
- low connectivity
Napo distal floodplain
0
100
200
300
400
0
10
20
40
60
80
10
0
# d
ays
depth (cm)
Napo floodplains
distal floodplain
proximal floodplain
• Large variability in flood
duration and depth.
• Proximity and hydrological
connectivity to river explain
depth and duration of
flooding.
• Elevation of sampling sites
relative to river unknown.
• Some sites may be on
perched terraces?
0
100
200
300
400
500
600
1
41
81
12
1
16
1
20
1
24
1
28
1
32
1
36
1
wa
ter
leve
l (c
m)
day
downstream upstream
0
100
200
300
400
500
600
0 25 50 75 100
wa
ter
leve
l (c
m)
% time
upstream downstream
Frequency: Napo River hydrographs
year 2009
Source: INAMHI-SENAMHI, Hybam Project.
• Higher frequency of
floods towards the
Andes.
• Inundation may act
more as an ecological
disturbance towards
the Andes.
# o
f flow
peaks/y
ear
0
100
200
300
400
0 25 50 75 100
wa
ter
leve
l (c
m)
% time
River 4
Distal floodplain 4
Proximal floodplain 4
0
100
200
300
400
0 25 50 75 100
wa
ter
leve
l (c
m)
% time
River
Distal floodplain 1
Proximal floodplain 1
Frequency: Floodplain hydrographs
upstream
downstream
2008-2009
0
100
200
300
400
wa
ter
leve
l (c
m)
River
Proximal floodplain 1
Distal floodplain 1
0
100
200
300
400
wa
ter
leve
l (c
m)
River 4
Distal floodplain 4
Proximal floodplain 4
Most floodplain sites showed shallow, continuous inundation
Timing and flashiness: Predictability
0
100
200
300
400
1
41
81
121
161
201
241
281
321
361
wa
ter
leve
l (m
)
day
upstream
2007
2008
2009
2010 0
100
200
300
400
500
600
1
41
81
121
161
201
241
281
321
361
wate
r le
vel (m
)
day
downstream
2007
2008
2009
2010
• Lower flood
predictability in
upstream reaches.
• Much flashier than
Central Amazon!
River control of floodplain inundation? In some places it may to some extent:
But often it doesn’t:
0
50
100
0 100 200 300 400 p
rox
ima
l fl
oo
dp
lain
2
wa
ter
leve
l (c
m)
Napo R. water level (cm)
0
100
200
0 100 200 300 400 pro
xim
al fl
oo
dp
lain
1 w
ate
r le
ve
l (c
m)
Napo R water level (cm)
0
50
100
0 100 200 300 400
dis
tal fl
oo
dp
lain
1 w
ate
r le
ve
l (c
m)
Napo R water level (cm)
0
50
100
0 100 200 300 400 Pro
xim
al fl
oo
dp
lain
3 w
ate
r le
ve
l (c
m)
Napo R. water levels (cm)
Caveat: only modest river floods occurred during the study
0
2
4
6
8
10
0 100 200 300 400
pro
xim
al fl
oo
dp
lain
4
wa
ter
leve
l (c
m)
Napo R. water level (cm)
0
50
100
0 100 200 300 400
dis
tal fl
oo
dp
lain
4 w
ate
r le
ve
l (c
m)
Napo R. water level (cm)
0
1
2
3
4
5
0 1 2 3
Mg2+
(mg/L)
Na
+ (
mg
/L)
Sources of flood water
• Major ions as
hydrological tracers
• Na+ and Mg2+ highest in
Andean rivers
• Lowland waters are
more dilute in ions
although similar in
proportions
Napo River (Andean)
Yasuní River (lowland)
• Floodplain waters
span the range from
river water to local
water
• Most are dominated
by local water
• Diversity of water
sources may increase
floodplain biodiversity
0
1
2
3
4
5
0 1 2 3
Mg2+
(mg/L)
Na
+ (
mg
/L)
Floodplain waters
along Napo River
Sources of flood water
Floodplain Hydrological Regimes Compared
Andean
Amazon Central
Amazon
Tropical
Australia
Dry
Season
Riverine inundation Erratic, short Predictable, long
Arid
Moist
Pantanal
Ecological implications: Do erratic floods matter?
Ecological phenomenon
Central
Amazon
Andean
Amazon
Aquatic macrophyte growth
and coverage
Abundant Sparse
Fish life cycles tied to flood
pulse
Closely Unknown –
perhaps less?
Flooding resets vegetation
succession
Sometimes Often (channel
migration)
Flooding as a filter for
terrestrial biota
Severe Lower
Dry season stress on
aquatic biota
Modest Lower
River-floodplain exchange
of organic matter, nutrients
High Modest
Acknowledgements
• Field assistants and local
guides.
• Local communities and
organizations
• Napo Wildlife Center & Sani
Lodge
• HYBAM Project - INAMHI
(Ecuador) & SENAMHI (Peru)
• World Wildlife Fund - Russell E. Train
Fellowship
• National Geographic Society - Committee
for Research & Exploration Grant
• National Science Foundation - Doctoral
Dissertation Improvement Grant
• Michigan State University: Center for Latin
American Studies , Center for Water
Sciences, College of Natural Sciences,
Graduate School, Kellogg Biological
Station