1. Laurence Maurice Bourgoin Jean-Michel Martinez Pascal Kosuth Julien 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 sediment transfer and storage along the Amazon River Case study : the Varzea of Lago Grande de Curuai Research agreement /

2. Study of the Hydrological and Study of the Hydrological and Suspended Sediment dynamics between the Amazon River and a floodplain Suspended Sediment dynamics between the Amazon River and a floodplain lakes system lakes system Estimating the sediment deposition rate Estimating the sediment deposition rate in an Amazonian floodplain in an Amazonian floodplain Case study : the Várzea of Lago Grande de Curuai Objectives

3. 0 600 km 3 rd 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)

4. 0 600 km Case study in the Middle Amazon floodplain : “várzea do Lago Grande de Curuai” Madeira R. Amazon R. Curuai floodplain 3 rd LBA Scientific Meeting

5. Tapajós R. Image MODIS 10/10/02 Resolution 250m 0100 km Santarém Study area: The Curuaí floodplain (PA) Amazonas R. Óbidos 3 rd LBA Scientific Meeting

6. Image MODIS 10/10/02 Resolution 250m 0100 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 3 rd LBA Scientific Meeting

7. Role of floodplains in sediment transfer and storage along the Amazon River METHODOLOGY Sediment Deposition: - Monitoring network - Multi temporal remote sensing images - Hydrological model Sediment Input: - Monitoring network - Field measurements 3 rd LBA Scientific Meeting

8. Role of floodplains in sediment transfer and storage along the Amazon River METHODOLOGY - 1 Varzea do Lago Grande de Curuai : Monitoring network

12. Resuspension process

14. Role of floodplains in sediment transfer and storage along the Amazon River Varzea do Lago Grande de Curuai : Field Campaigns

15. Role of floodplains in sediment transfer and storage along the Amazon River METHODOLOGY - 3 Varzea do Lago Grande de Curuai : Reservoir model Water flux exchanged between the main channel and = the floodplain

16. Role of floodplains in sediment transfer and storage along the Amazon River Assessment of the flooded areas / lake stage relationship :  V calculation  Lake water storage : 9.4  1.5 km³ (Martinez et al. 2003) V storage

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19. Annual hydrological balance (2000-2003) Curuai floodplain lakes 6 - 8 km 3 (2000) (2002) 9,3 - 11 km 3 (2003) (2001)

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22. 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

23. Annual Deposition rate Curuai floodplain lakes 0.3-0.5 10 6 t/y 600-800 10 6 t/y

24. SEDIMENT DEPOSITION RESULTS IN AMAZONIAN FLOODPLAINS 400,000 t/y 174 t km -2 y -1 120 10 6 t/y 2400 t km -2 y -1

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26. 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

27. 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 3 rd LBA Scientific Meeting

28. Thanks for your attention! 3 rd LBA Scientific Meeting