El agua en la llanura pampeana:
desde los humedales primigenios
hasta su transformación para las actividades agropecuarias
Rolando Quirós, Hugo T. von Bernard y María B. Boveri
Area de Sistemas de Producción AcuáticaFacultad de Agronomía, Universidad de Buenos Aires
Conference presented to V SEMINARIO INTERNACIONAL CYTED-XVII: "Un enfoque integrado para la gestión sustentable del agua. Experiencias en zonas húmedas". CETA, FVET, UBA, 6- 8 de abril 2005, Buenos Aires, Argentina.
© 2005 Quirós
the Pampas
1. Rolling
2. Central
3. Central
4. Southern
5. Mesopotamian
6. Flooding
from Viglizzo et al., 2001
the pampean wetlands
1. Rolling
2. Central
3. Central
4. Southern
5. Mesopotamian
6. Flooding
from Viglizzo et al., 2001
factors that determine the main characteristics of thepampean wetlands
• geomorphology of the plains
• climate
• climate variability
• long-term variability
• short-term variability
• seasonal variability
geomorphology of the plains (1)
UPLAND HIGH MIDSLOPE LOW MIDSLOPE LOWLAND SHALLOW LAKES TEMPORARY
STREAMS
STREAMSRIVERS
CANALS
0.1 to 0.5 % 0.5 to 3 % or more 1 to 0.5 % less than 0.5 % extremely low slope
geomorphological unitmodified from Fuschini Mejia, 1994
Compound longitudinal dunes (pleistocene)
Simple longitudinal dunes (holocene)
Megaparabolic dunes (holocene)
geomorphology of the plains (2)
from Malagnino, 1988
geomorphology of the plains (3)
landscape slopes (m/km)
0.03
long-term climate variability of the plains (1)
0
200
400
600
800
1000
1200
1400
1600
1918/19 1928/29 1938/39 1948/49 1958/59 1968/69 1978/79 1988/89 1998/99
Campaña
Prec
ipita
ción
(mm
)
Anual Obs Ciclo Promedio
from Pérez et al., 2003
long-term climate variability of the plains (2)
300
500
700
900
1100
1300
1500
1874/75 1894/95 1914/15 1934/35 1954/55 1974/75 1994/95 2014/15 2034/35Campañas
Prec
ipita
cion
es a
nual
es (m
m)
Pp Calculada Pp Observada
from Sierra et al., unpublished
?
short-term climate variability in the plains
Salado river discharge
020406080
100120140160180200
Q (m
3/se
c)
noviembre 2001
los lagos someros (lagunas):
componente central del humedal pampeano
satellital imagens from Instituto de Clima y Agua, INTA
octubre 1997
Descarga Río Salado
0
20
40
60
80
100
120
140
160
180
200
Q (m
3/se
g)
marzo 1998
Descarga Río Salado
0
20
40
60
80
100
120
140
160
180
200
Q (m
3/se
g)
febrero 1999
Descarga Río Salado
0
20
40
60
80
100
120
140
160
180
200
Q (m
3/se
g)
noviembre 2001
Descarga Río Salado
0
20
40
60
80
100
120
140
160
180
200
Q (m
3/se
g)
0
2
4
6
8
10
verano invierno verano invierno verano invierno
cond
uctiv
idad
elé
ctric
a (m
S/cm
, 25
o C)
0
10
20
30
40
50
60
70
80
90
100
desc
arga
río
Sala
do (m
3/se
g)
sequía
inundación
sequía
inundación
sequía
inundación
sequía
1999 2000 2001
ciclo sequía – inundación característico del humedal pampeano“ inundación” en la sequía y “sequía” en la inundación
seasonal variability in very shallow lake salinity is includedRosso and Rennella, unpublished data
lake morphology (1)
-3
-2
-1
00 25 50 75 100
porcentaje de la superficie
Z (m
)
-3
-2
-1
00 25 50 75 100
porcentaje de la superficie
Z (m
)
-3
-2
-1
00 25 50 75 100
porcentaje de la superficie
Z (m
)
un 70% de la superficie de una laguna pampeana tiene profundidades mayores a la profundidad media
lake morphology (2)
-100
-80
-60
-40
-20
0
0 20 40 60 80 100desarrollo del volumen (%)
desa
rrol
lo d
e la
pro
fund
idad
(%)
un 75-80 % del volumen de una laguna pampeana se encuentra por encima de su profundidad media
lake morphology (3)
Zmaxima (m)
Zm
edia
(m)
0
1
2
3
4
5
6
0 1 2 3 4 5 6 7 8 9
profundidad media = 0.7 profundidad máximaforma de cubeta: semi elipsoide de revolución
primordial grasslands
an hypothetical landscape for primordial pampean wetlands
current grasslands (1)
fotos: INTA
current grasslands (2)
fotos: INTA
from Guerschman et al., 2001
current grasslands (3)
environmental efforts on the pampean wetlands
• dredging, canalization and damming of water bodies
• changes in land use patterns
• increased land erosion
• agriculture (pastures, implanted pastures, annual crops, extensive livestock growing, animal feed-lots)
• unregulated urbanization with deficient or without sewage treatment works
• unregulated land-fill usually with toxic substances
environmental effects in the pampean wetlands
• changes in natural hydrological patterns
• changed morphology of water bodies
• increased inorganic sedimentation
• increased levels of non-oxidized organic matter and its metabolites
• nutrient enrichment (mainly P and N)
• contamination of surface waters and groundwater with toxic substances commonly used in modern agriculture (herbicides, insecticides, and other agro-toxic substances)
• contamination of surface waters and groundwater (?) with highly toxic substances used in industry
• huge changes in vegetal and animal biodiversity and abundance for both terrestrial and aquatic ecosystems
“legal” canals (1)
foto: INTA Anguil
“legal” canals (2)
foto: Hugo Dias
“illegal” canals
foto: Municipio Mar Chiquita
Central Pampas
0
20
40
60
80
100
1881 1914 1937 1960 1988 2002
natural pastures cultivated pastures annual crops modified from Viglizzo et al., 2001
Flooding Pampas
0
20
40
60
80
100
1881 1914 1937 1960 1988 2002
natural pastures cultivated pastures annual crops modified from Viglizzo et al., 2001
Total Pampas
0
20
40
60
80
100
1881 1914 1937 1960 1988 2002natural pastures cultivated pastures annual crops
"natural" land
0
10
20
30
40
50
1881 1914 1937 1960 1988 2002
mill
ions
of h
ecta
res
Central Pampas Flooding Pampas Total Pampasmodified from Viglizzo et al., 2001
fertilizers use
0
100
200
300
400
500
600
700
800
900
1000
1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001
year
fert
ilize
rs u
se (k
g 10
-6/y
r)
K N P
source: FAO
pesticides use
0
20
40
60
80
100
120
140
160
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
year
pest
icid
es (m
illio
ns k
g or
l/yr
)
herbicides insecticides fungicides other
source: SAGPyA
PCB´s in water and fish
Descarga Río Salado
0
20
40
60
80
100
120
140
160
180
200
Q (m
3/se
g)
0.0
0.4
0.8
1.2
1.6
2.0
7 8 9 10 11 12 1 2 3 4 2000-2001
PCB
´s in
wat
er (u
g/L)
0
3
6
9
12
15
18
PCB
´s in fish liver (ug/kg)
water fish
lagunas “claras” y “turbias” como indicadores de la intensidad de acción antrópica sobre el humedal pampeano
"natural" land
0
10
20
30
40
50
1881 1914 1937 1960 1988 2002
mill
ions
of h
ecta
res
Central Pampas Flooding Pampas Total Pampas
lagunas “claras” lagunas “turbias”
37 lagunas pampeanas, “turbias” (O) y “claras” (O)
100
101
102
103
101 102 103 104
TP (mg/m3)
Chl
(mg/
m3)
-3
-2
-1
0
1
2
3
-3 -2 -1 0 1 2 3PCA - 2
PCA
- 1
“claras”
“turbias” planctívoros
piscívoros TN:TP
MASI
nutrientesfitoplancton
“claras” y “turbias”
“claras” y “turbias”
-3
-2
-1
0
1
2
3
-3 -2 -1 0 1 2 3
1
1
11 1
1
4
11
11
1
24
23
3
3
4
3
3
33 2
22
444
4
4444
PCA - 2
PCA
- 1
100
101
102
103
101 102 103 104
TP (mg/m3)
Chl
(mg/
m3)
“claras” y “turbias”
flooding pampas
central pampas
central pampas
flooding pampas
for pampean terrestrial ecosystems, dramatic changes in weighted biodiversity have been widely documented for vegetal and animal communities, therefore, only some changes in the biota of the aquatic component of the pampean wetlands will be presented here:
lake phytoplankton“clear” and “turbid” lakes
0
20
40
60
80
100
1 2clear = 1 turbid = 2
% c
yano
bact
eria
100
101
102
103
104
105
1 2clear = 1 turbid = 2
# cy
anob
acte
ria
lake fish changes from “clear” to “turbid” very shallow pampean lakes
water transparency = 1.50 m
"clear" lakes
visual planktivores
35%
top predator16%
detritivorous17%
other24%filter feeding
planktivores0%
carp8%
"turbid" lakes
carp3%
filter feeding planktivores
1%
other17%
detritivorous20%
top predator5%
visual planktivores
54%
water transparency = 0.38 m
upper Salado "turbid" lakes
visual planktivores
52%
top predator3%
detritivorous10%
other4%filter feeding
planktivores21%
carp10%
water transparency = 0.23 m
from primordial wetlands to agricultural land
• natural grasslands• natural drainages
• “clear” lakes• macrophyte dominated• usually with oxic, P unsaturated
sediments• balanced vegetal and animal
communities• relatively low levels of organic
matter, more oxidative environments• nutrient levels according to drainages
on highly productive soils
• agriculture, human settlements and highly modified grasslands
• drainages medium to highly modified
• “turbid” lakes• phytoplankton dominated• hypoxic and anoxic, P saturated
sediments • simplified vegetal and animal
communities• high levels of organic matter,
reductive environments• very high nutrient levels due to
agriculture and urbanization• extended fish and avian mortalities• human health hazards
past present
“son preferibles dos años de inundación a un año de sequía”
Anónimo