Laurence Maurice Bourgoin Jean-Michel Martinez Pascal Kosuth Julien Grelaud (IRD, Institut de...

Laurence Maurice BourgoinJean-Michel Martinez

Pascal KosuthJulien Grelaud

(IRD, Institut de Recherche pour le Développement)

and Eurides de Oliveira(ANA, Agencia Nacional de Aguas)

Surface Hydrology and Water Chemistry

Role of floodplains in suspended Role of floodplains in suspended sediment transfer and storage along sediment transfer and storage along

the Amazon Riverthe Amazon River

Case study : the Varzea of Lago Grande de Case study : the Varzea of Lago Grande de Curuai Curuai

Research agreementResearch agreement //

• Study of the Hydrological and Study of the Hydrological and Suspended Suspended SSediment dynamicsediment dynamics between the Amazon River and a between the Amazon River and a floodplainfloodplain lakes systemlakes system

• Estimating the sediment deposition Estimating the sediment deposition rate rate in in an Amazonian an Amazonian floodplainfloodplain

Case study : the Várzea of Lago Grande de Case study : the Várzea of Lago Grande de Curuai Curuai

ObjectivesObjectives

0 600 km

3rd LBA Scientific Meeting

Floodplain surface area estimation for the whole Amazon basin: 610,000 km² (±67,000) ~ 10% total drainage area

(Martinez et al., in press)

0 600 km

Case study in the Middle Amazon floodplain : Case study in the Middle Amazon floodplain : ““várzea do Lago Grande de Curuai”várzea do Lago Grande de Curuai”

Madeira R

.

Amazon R.Curuai floodplain


Tapajós R.

Image MODIS 10/10/02Resolution 250m

0 100 km

Santarém

Study area: The Curuaí floodplain (PA)

Amazonas R.

Óbidos


Image MODIS 10/10/02Resolution 250m

0 100 km

Santarém

Study area: The Curuaí floodplain (PA)

Amazonas R.

Location: 55.43°W / 2.18°S

Distance to the Ocean: 900 km

System length : 126km

River level fluct. : 7m

River gradient : 0.5 m / 2.0 m

Mean ann. rainfall : 2000 mm (Juruti) to 2500 mm (Curuai)

Mean ann. ETR : 1400 mm

Watershed Area : 3660 km²

Flooded area : 700 / 2300 km²


Role of floodplains in sediment transfer and storage along the Role of floodplains in sediment transfer and storage along the Amazon RiverAmazon River

METHODOLOGYMETHODOLOGY

Sediment Deposition:Sediment Deposition:- Monitoring network- Multi temporal remote sensing images- Hydrological model

Sediment Input:Sediment Input:- Monitoring network - Field measurements



METHODOLOGY - 1METHODOLOGY - 1Varzea do Lago Grande de Curuai : Monitoring Varzea do Lago Grande de Curuai : Monitoring

networknetwork

TSS monitoring results in floodplain channels (Curuai)

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TS

S (

mg

/l)

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)

Obidos Obidos water level


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Obidos Ponto Seguro Obidos water level


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Obidos Foz Lago Grande Boca Norte Ponto Seguro Obidos water level


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Obidos Foz Lago Grande Boca Norte Ponto Seguro Obidos water level

Resuspension process

TSS monitoring results in white water floodplain lakes (Curuai)

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Curuai Lago do Poção Boca Lago do Poção

Sao Nicolau Lago Grande A03 Obidos_hydrogram

Water level 2003

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n-02 d-02 j-03 f-03 m-03 a-03 m-03 j-03 j-03 a-03 s-03 o-03 n-03 d-03

Curuai


Varzea do Lago Grande de Curuai : Field Varzea do Lago Grande de Curuai : Field CampaignsCampaigns


METHODOLOGY - METHODOLOGY - 33Varzea do Lago Grande de Curuai : Reservoir Varzea do Lago Grande de Curuai : Reservoir

modelmodel

Q V EV P I Water flux exchanged between the main channel

and = the floodplain

Role of floodplains in sediment transfer and storage along the Role of floodplains in sediment transfer and storage along the Amazon RiverAmazon River Q V EV P I

Assessment of the flooded areas / lake stage relationship : V calculation

Lake water storage : 9.4 1.5 km³ (Martinez et al. 2003)

WaterHigh

WaterLow

H

Hstorage dhhV )(

Vstorage

Water flux exchange between the floodplain lakes and the Amazon River(normalized to the Obidos discharge)

-2.5

-2

-1.5

-1

-0.5

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oct-03

%

Qfloodplain/Qriver obtained by the model

Qfloodplain/Qriver measured in the field

Flo

odpl

ain

lake

s fil

ling

upO

utflo

w


Monthly liquid fluxes between the floodplain and the main channel

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-1

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Liquid fluxes (en km3)

Annual hydrological balance (2000-2003)Curuai floodplain lakes

6 - 8 km3

(2000) (2002)

9,3 - 11 km3

(2003) (2001)


TSS measured in Obidos _ 2001

y = 4.4232x - 423.24

R2 = 0.9332

y = -1.9945x + 550.35

R2 = 0.9857

y = 0.0935x + 18.974

R2 = 0.50750

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Discharge (10^3 m3/s)

TSS

(m

g/l)

10-nov-00 au 30-janv-01 10-fev-01 au 20-mai-01 20-mai-01 au 30-oct-01


Monthly liquid and solid fluxes between the floodplain and the main channel

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Liquid fluxes (en km3) Solid fluxes (10 5̂ t)

Annual sedimentological balance (2000-2003)Curuai floodplain lakes

(2001)

849 000 t

(2002)

879 000 t

(2003)

909 500 t

(2001)

496 000 t

(2002)

504 000 t

(2003)

498 000 t

Annual Deposition rateCuruai floodplain lakes

0.3-0.5106 t/y

600-800106 t/y

SEDIMENT DEPOSITION RESULTS IN AMAZONIAN FLOODPLAINS

400,000 t/y

174 t km-2 y-1

120 106 t/y

2400 t km-2 y-1

Hydrological control of the [Hg] at the Obidos station (Amazon R.) - Field surveys measurements

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f m a m j j a s o n d j f m a m j j a s o n d j f m a m j j a s o n d

P-H

g (

ng

/g)

an

d w

ate

r le

ve

l (c

m)

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D-H

g (

ng

/l)

Water level

P-Hg (ng/g)

D-Hg (ng/l)

2001 2002 2003


Hg DEPOSITION RESULTS IN AMAZONIAN FLOODPLAINS

~ 0.2 t Hg/y(10% daily P-Hg flux)

~76 g P-Hg km-2 y-1

~ 4.5 t Hg/y(14% annual T-Hg flux)

~ 90 g P-Hg km-2 y-1

•Floodplain lake levels are very close (tens of centimeters) to river water levels

•The output of water from the floodplain lakes to the main channel begins at the flood peak

•Water and sediment outflow max. are observed during the low water stage

•Main sedimentation occurs in the western part of the varzea, generating a widening land strip

•Sediment storage and Hg associated with fine particles appears to be more important in the upstream foreland basins than along the mid-Amazon floodplains

Conclusions


Thanks for your attention!


Laurence Maurice Bourgoin Jean-Michel Martinez Pascal Kosuth Julien Grelaud (IRD, Institut de...

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