Suspended sediment dynamics in the Amazon River of Peru Elisa Armijos a , Alain Crave b, c, * , Philippe Vauchel d , Pascal Fraizy d , William Santini d , Jean-Sèbastien Moquet e , Nore Arevalo f , Jorge Carranza g , Jean-Loup Guyot h a LBA, Instituto Nacional de Pesquisas da Amazônia (INPA), Universidade do Estado do Amazonas (UEA), Av. André Araújo, 2936, Aleixo, CEP 69060-001, Manaus, Brazil b Géoscience Rennes, CNRS/INSU UMR 6118, Campus de Beaulieu, 35042 Rennes, France c Université de Rennes 1, Campus de Beaulieu, 35042 Rennes, France d GET (CNRS, IRD, OMP, Université de Toulouse),14 Avenue Edouard Belin, 31400 Toulouse, France e Universidade de São Paulo, Instituto de Geociencias, Rua do lago, 562, cidade Universitária São Paulo, São Paulo, Brazil f UNALM, Universidad Nacional Agraria La Molina, Facultad de Ingeniería Agrícola, Avenida La Molina s/n, Lima 12, Peru g SENAMHI e DGH Servicio Nacional de Meteorología e Hidrología, Dirección General de Hidrología, Casilla 11-1308, Lima 11, Peru h GET (CNRS, IRD, OMP, Université de Toulouse), IRD, CP 7091 Lago Sul, CEP 71635-971 Brasília, DF, Brazil article info Article history: Received 15 December 2011 Accepted 7 September 2012 Keywords: Hydrology Sedimentation Erosion Andes Sediment transport Andean piedmont abstract The erosion and transport of sediments allow us to understand many activities of significance, such as crust evolution, climate change, uplift rates, continental processes, the biogeochemical cycling of pollutants and nutrients. The Amazon basin of Peru has contrasting physiographic and climatic char- acteristics between the Andean piedmont and the plains and between the north and south of the basin which is why there are 8 gauging stations located along the principal rivers of the Andean piedmont (Marañón, Huallaga, Ucayali) and the plain (Marañón, Tigre, Napo, Ucayali and Amazon rivers). Since 2003, the ORE-Hybam (IRD-SENAMHI-UNALM) observatory has performed out regular measurements at strategic points of the Amazon basin to understand and model the systems, behavior and long-term dynamics. On the Andean piedmont, the suspended yields are governed by a simple model with a relationship between the river discharge and the sediment concentration. In the plain, the dilution effect of the concentrations can create hysteresis in this relationship on a monthly basis. The Amazon basin of Peru has a sediment yield of 541 *10 6 t year 1 , 70% comes from the southern basin. Published by Elsevier Ltd. 1. Introduction Erosion and transport processes are key factors for under- standing the dynamics of natural systems of different scales. Among other factors, the influence of erosion processes on mountain range dynamics is one of the crucial points for understanding climate and tectonic feedback (Willet, 1999; Molnar, 2003). How earth materials transit from mountain ranges to oceans in terms of mass and time is still an open question. Erosive processes are sensitive to many factors such as temperature, rainfall, runoff, landscape character- istics, lithology, and significantly anthropogenic activities (Walling, 2006). The challenge is to understand the respective effects of these factors on erosion rates at different scales. The suspended sediment load in rivers integrates the upstream to downstream balance of all erosion processes in the hydrological basin. Therefore, suspended sediment load provide information on present-day mean catchment denudation rates and on the dynamic response to climate inputs under specific geological and anthropo- genic contexts (Dadson et al., 2003; Walling, 2006). However, sus- pended sediment load is a complex signal resulting from numerous factors. Currently, there is no evidence of the relative dominance of each factor. Climate and tectonic factors are the relevant parameters at large spacial and temporal scales because they fix the potential of mass that can be eroded and the amount of water needed to trans- port the sediments. Therefore, mountain ranges with high climatic gradients are interesting contexts within which to interpret sus- pended sediment loads in terms of transport efficiency. The Amazon basin in Peru presents several advantages for studying erosion/transport processes. Firstly, the Andes, which cover the upstream part of the basin, are one of the world’s highest mountain ranges, with an average elevation of 4000 m (m asl). Second, there are pluviometric contrasts between the southern tropical and equatorial hydrological regimes (Espinoza et al., 2009b). Third, there is a low rate of erosion due to anthropogenic activity. Since 2003, the observatory ORE-Hybam (IRD-SENAMHI- UNALM) has been performing out regular measurements in * Corresponding author. Géoscience Rennes, CNRS/INSU UMR 6118, Campus de Beaulieu, 35042 Rennes, France. E-mail address: alain.crave@univ-rennes1.fr (A. Crave). Contents lists available at SciVerse ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames 0895-9811/$ e see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jsames.2012.09.002 Journal of South American Earth Sciences xxx (2012) 1e10 Please cite this article in press as: Armijos, E., et al., Suspended sediment dynamics in the Amazon River of Peru, Journal of South American Earth Sciences (2012), http://dx.doi.org/10.1016/j.jsames.2012.09.002