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Abstract ID: 236
Floodplain hydrology as a tool in interpreting chemical heterogeneities in an Amazon floodplain lake (Lago Grande de Curuaí)
The floodplains of the Amazon basin influence the hydrology and fluxes of suspended solids and solutes at multiple scales. Our study focused on the floodplain of Lago Grande de Curuai (Obidos, Brazil), a 4000 km2 segment including its local upland catchment representative of the lower Amazon floodplain. This floodplain contains large lakes connected to the mainstem river by several channels. In this study, we proposed an analysis tool for interpreting chemical heterogeneities within the floodplain. Based on in situ and satellite data acquired from 1997 through 2003, we firstly calculated water exchanges between the floodplain and the river and described the temporal dynamics of lake water derived from river flooding, rainfall, runoff, and exchange with groundwater over six years. The Amazon River dominated the inputs of water to the lake year-round, accounting about 77% of the annual total; rainfall and runoff accounted for about 9% and 10%, respectively while seepage from groundwater system accounted for 4%. The hydrologic residence time of the lake is about 3 months, and the floodplain always was a net contribution of water to the river. The exported volume varied between 4.2 and 7.3 km3 depending on water year and represented about 0.75 times the maximal storage reached each year. Following this step, based on monthly major elements concentration, we calculated solute balances and identified non-conservative elements. In a third step, we proposed an analysis of chemical element behaviour within the floodplain calculating water and solute temporal dynamics for each lake constituting the floodplain. Finally, comparing conservative and non-conservative elements behaviour within the floodplain serves identifying main biogeochemical processes involved in changing concentration of non-conservative elements.
Session: Biogeochemistry - Floodplain ecosystem processes.
Presentation Type: Oral
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