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from Sierra et al., unpublished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