Browsing by Author "Cochonneau, Gérard"
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Item Restricted A reassessment of the suspended sediment load in the Madeira River basin from the Andes of Peru and Bolivia to the Amazon River in Brazil, based on 10 years of data from the HYBAM monitoring programme(Elsevier, 2017-10) Vauchel, Phillippe; Santini, William; Guyot, Jean Loup; Moquet, Jean Sébastien; Martínez, Jean Michel; Espinoza, Jhan Carlo; Baby, Patrice; Fuertes, Oscar; Noriega, Luis; Puita, Oscar; Sondag, Francis; Fraizy, Pascal; Armijos Cardenas, Elisa Natalia; Cochonneau, Gérard; Timouk, Franck; Olivera, Eurides de; Filizola, Naziano; Molina, Jorge; Ronchail, JosyaneThe Madeira River is the second largest tributary of the Amazon River. It contributes approximately 13% of the Amazon River flow and it may contribute up to 50% of its sediment discharge to the Atlantic Ocean. Until now, the suspended sediment load of the Madeira River was not well known and was estimated in a broad range from 240 to 715 Mt yr⁻¹. Since 2002, the HYBAM international network developed a new monitoring programme specially designed to provide more reliable data than in previous intents. It is based on the continuous monitoring of a set of 11 gauging stations in the Madeira River watershed from the Andes piedmont to the confluence with the Amazon River, and discrete sampling of the suspended sediment concentration every 7 or 10 days. This paper presents the results of the suspended sediment data obtained in the Madeira drainage basin during 2002–2011. The Madeira River suspended sediment load is estimated at 430 Mt yr⁻¹ near its confluence with the Amazon River. The average production of the Madeira River Andean catchment is estimated at 640 Mt yr⁻¹ (±30%), the corresponding sediment yield for the Andes is estimated at 3000 t km⁻² yr⁻¹ (±30%), and the average denudation rate is estimated at 1.20 mm yr⁻¹ (±30%). Contrary to previous results that had mentioned high sedimentation rates in the Beni River floodplain, we detected no measurable sedimentation process in this part of the basin. On the Mamoré River basin, we observed heavy sediment deposition of approximately 210 Mt yr⁻¹ that seem to confirm previous studies. But while these studies mentioned heavy sedimentation in the floodplain, we showed that sediment deposition occurred mainly in the Andean piedmont and immediate foreland in rivers (Parapeti, Grande, Pirai, Yapacani, Chimoré, Chaparé, Secure, Maniqui) with discharges that are not sufficiently large to transport their sediment load downstream in the lowlands.Item Restricted Contrasting regional discharge evolutions in the Amazon basin (1974–2004)(Elsevier, 2009-09-15) Espinoza, Jhan Carlo; Guyot, Jean Loup; Ronchail, Josyane; Cochonneau, Gérard; Filizola, Naziano; Fraizy, Pascal; Labat, David; Oliveira, Eurides de; Ordoñez, Juan Julio; Vauchel, PhillippeFormer hydrological studies in the Amazon Basin generally describe annual discharge variability on the main stem. However, the downstream Amazon River only represents the mean state of the Amazonian hydrological system. This study therefore uses a new data set including daily discharge in 18 sub-basins to analyze the variability of regional extremes in the Amazon basin, after recalling the diversity of the hydrological annual cycles within the Amazon basin. Several statistical tests are applied in order to detect trends and breaks in the time series. We show that during the 1974–2004 period, the stability of the mean discharge on the main stem in Óbidos is explained by opposite regional features that principally involve Andean rivers: a decrease in the low stage runoff, particularly important in the southern regions, and an increase in the high stage runoff in the northwestern region. Both features are observed from the beginning of the nineties. These features are also observed in smaller meridian sub-basins in Peru and Bolivia. Moreover we show that the changes in discharge extremes are related to the regional pluriannual rainfall variability and the associated atmospheric circulation as well as to tropical large-scale climatic indicators.Item Open Access Discharge simulation in the sub-basins of the Amazon using ORCHIDEE forced by new datasets(European Geosciences Union (EGU), 2012-03-22) Guimberteau, Matthieu; Drapeau, Guillaume; Ronchail, Josyane; Sultan, Benjamin; Polcher, Jan; Martinez, Jean-Michel; Prigent, Catherine; Guyot, Jean-Loup; Cochonneau, Gérard; Espinoza, Jhan Carlo; Filizola, N.; Fraizy, P.; Lavado, W.; De Oliveira, E.; Pombosa, R.; Noriega, L.; Vauchel, P.The aim of this study is to evaluate the ability of the ORCHIDEE land surface model to simulate streamflows over each sub-basin of the Amazon River basin. For this purpose, simulations are performed with a routing module including the influence of floodplains and swamps on river discharge and validated against on-site hydrological measurements collected within the HYBAM observatory over the 1980–2000 period. When forced by the NCC global meteorological dataset, the initial version of ORCHIDEE shows discrepancies with ORE HYBAM measurements with underestimation by 15 % of the annual mean streamflow at Obidos hydrological station. Consequently, several improvements are incrementally added to the initial simulation in order to reduce those discrepancies. First, values of NCC precipitation are substituted by ORE HYBAM daily in-situ rainfall observations from the meteorological services of Amazonian countries, interpolated over the basin. It highly improves the simulated streamflow over the northern and western parts of the basin, whereas streamflow over southern regions becomes overestimated, probably due to the extension of rainy spots that may be exaggerated by our interpolation method, or to an underestimation of simulated evapotranspiration when compared to flux tower measurements. Second, the initial map of maximal fractions of floodplains and swamps which largely underestimates floodplains areas over the main stem of the Amazon River and over the region of Llanos de Moxos in Bolivia, is substituted by a new one with a better agreement with different estimates over the basin. Simulated monthly water height is consequently better represented in ORCHIDEE when compared to Topex/Poseidon measurements over the main stem of the Amazon. Finally, a calibration of the time constant of the floodplain reservoir is performed to adjust the mean simulated seasonal peak flow at Obidos in agreement with the observations.Item Restricted Indirect assessment of sedimentation in hydropower dams using MODIS remote sensing images(Remote Sensing, 2019-02-05) Condé, Rita de Cássia; Martinez, Jean-Michel; Pessotto, Marco Aurélio; Espinoza Villar, Raúl Arnaldo; Cochonneau, Gérard; Henry, Raoul; Lopes, Walszon; Nogueira, MarcosIn this study, we used moderate resolution imaging spectroradiometer (MODIS) satellite images to quantify the sedimentation processes in a cascade of six hydropower dams along a 700-km transect in the Paranapanema River in Brazil. Turbidity field measurement acquired over 10 years were used to calibrate a turbidity retrieval algorithm based on MODIS surface reflectance products. An independent field dataset was used to validate the remote sensing estimates showing fine accuracy (RMSE of 9.5 NTU, r = 0.75, N = 138). By processing 13 years of MODIS images since 2000, we showed that satellite data can provide robust turbidity monitoring over the entire transect and can identify extreme sediment discharge events occurring on daily to annual scales. We retrieved the decrease in the water turbidity as a function of distance within each reservoir that is related to sedimentation processes. The remote sensing-retrieved turbidity decrease within the reservoirs ranged from 2 to 62% making possible to infer the reservoir type and operation (storage versus run-of-river reservoirs). The reduction in turbidity assessed from space presented a good relationship with conventional sediment trapping efficiency calculations, demonstrating the potential use of this technology for monitoring the intensity of sedimentation processes within reservoirs and at large scale.Item Open Access Influencia de la precipitación sobre los flujos de sedimentos en el Amazonas: una síntesis basada en 20 años de monitoreo(Instituto Geofísico del Perú, 2020-04) Armijos Cardenas, Elisa Natalia; Crave, Alain; Espinoza, Jhan Carlo; Filizola, Naziano; Espinoza-Villar, Raúl; Ayes, Irma; Fonseca, Paula; Fraizy, Pascal; Gutierrez, Omar; Vauchel, Philippe; Camenen, Benoit; Martiınez, Jean Michel; Dos Santos, André; Santini, William; Cochonneau, Gérard; Guyot, Jean LoupLa vida en la región amazónica está principalmente relacionada con la estacionalidad del régimen hidrológico fluvial. La riqueza de la biodiversidad y productividad de la llanura de inundación depende de los nutrientes y la materia orgánica que son transportados por los ríos en los sedimentos en suspensión, desde los Andes hacia el océano Atlántico. Sin embargo, poco se conoce sobre la influencia de la variabilidad hidrológica y pluvial en los flujos sedimentarios. Para abordar esta brecha, analizamos 3069 muestras superficiales de agua y sedimentos recolectadas en el centro del río, cada 10 días durante el período 1995-2014, en 6 estaciones ubicadas en el río Amazonas y sus tributarios. Este análisis se ha realizado haciendo una distinción del tamaño de las partículas, sedimentos finos (arcilla y limo) y sedimentos gruesos (arena). Considerando esta distinción, se estimó, por primera vez, que en la llanura amazónica predomina el flujo de sedimento fino con un 60 % y las arenas representan el 40 % complementario. La lluvia tiene una relación con la producción de sedimentos finos, mientras que el caudal rige el transporte de arenas en suspensión. Adicionalmente, este trabajo presenta el tiempo de respuesta entre la lluvia y el caudal. Los resultados obtenidos en este estudio son una contribución importante a la dinámica biológica y geomorfológica en la cuenca del Amazonas.Item Open Access Las resurgencias del Alto Mayo (San Martin, Perú): estudio hidrológico sobre un karst tropical andino-amazónico(Sociedad Geológica del Perú, 2018) Grandjouan, Olivier; Hidalgo, Liz; Apaéstegui Campos, James Emiliano; Baby, Patrice; Cochonneau, Gérard; Condori, Elmer; Espinoza, Jhan Carlo; Fraizy, Pascal; Huaman, Darwin; Jourde, Hervé; Mazzilli, Naomi; Morera Julca, Sergio Byron; Peña, Fluquer; Renou, Fabien; Robert, Xavier; Santini, William; Sifeddine, Abdel; Guyot, Jean LoupEl macizo kárstico del Alto Mayo (San Martin, Perú) tiene una red de drenaje desarrollada, activa y poco estudiada. El propósito de este estudio es determinar los caudales de las resurgencias y sus cuencas hidrográficas correspondientes. Los datos hidrológicos y pluviométricos utilizados provienen de los observatorios locales (ANA y SENAMHI) y del proyecto KarstAm. Los caudales medidos alcanzan hasta 24 m³/s en promedio para algunas resurgencias, situándolas entre las más grandes de Sur América. La poca variabilidad temporal del caudal de uno de los acuíferos (Río Negro) muestra un comportamiento atípico en relación a los acuíferos kársticos, pareciéndose más a un acuífero poroso. Los caudales específicos de las cuencas topográficas son superiores a la tendencia regional, por lo que las cuencas hidrográficas han sido recalculadas suponiendo la presencia de captación kárstica. Los datos de precipitación han sido corregidos con el método del vector regional. Los caudales específicos recalculados son más cercanos a los valores regionales, aunque se mantienen con elevados coeficientes de escurrimiento. Estos errores son atribuidos a una subestimación general de las precipitaciones en la cuenca del Alto Mayo.Item Restricted The flood recession period in western Amazonia and its variability during the 1985–2015 period(Elsevier, 2018-02) Ronchail, Josyane; Espinoza, Jhan Carlo; Drapeau, Guillaume; Sabot, Manon; Cochonneau, Gérard; Schor, TatianaStudy region The upper Amazon River, where the water level measured at the Tamshiyacu station (Peru) shows seasonal variability of seven meters. Study focus Key parameters for the flood recession period (beginning, end and duration of the low-water period, velocity of water falling and rising, and inversions in the direction of stage change known as “repiquete” events) are analyzed for the period 1985–2015, along with their relationship to rainfall integrated in the upper Amazon basin at Tamshiyacu. New hydrological insights the low-water period lasts about four months, beginning, on average, at the end of July and ending in early November. Since the late 1990s, the low-water period has tended to end later, last longer and the flood recession ends more abruptly than it used to. This may be related to the increased frequency of dry days during the austral winter in the central and southern part of the basin and to increased and more intense rainfall in late spring (November–December). Repiquete events are frequent, 8 each year on average, and sometimes very acute: 18 events with a water-level reversal greater than one meter were registered during the 1985–2015 period. They are related to unusual, intense and extended rainfall during the week preceding the repiquete. Extensions of this preliminary work are suggested, as well as possible implications for recessional agriculture.