Produção Nacional
Assessment of wash load transport in the Araguaia River (Aruanã Gauge Station), Central Brazil
2009; Volume: 16; Issue: 2 Linguagem: Inglês
ISSN
1851-4979
AutoresSâmia Aquino, Edgardo M. Latrubesse, Maximiliano Bayer,
Tópico(s)Geological formations and processes
ResumoWith an area close to 377,000 km 2 and a mean annual discharge of ~ 6,420 m 3 s -1 the Araguaia River is the main river draining the central highlands of Brazil. The Araguaia Rivers is a particularly sandy anabranching system that has been suffering geomorpholo- gic and sedimentary changes because of the effect of high rates of deforestation during the last decades. Little is known, however, on the amount of wash load transport. We will present the first relatively systematic results on wash load transport for the Araguaia River at the Aruana gauge station. The drainage area at Aruana is 77,000 km 2 and the mean annual discharge is ~1,200 m 3 s -1 . A total of 140 samples from 20 field surveys were analyzed and the wash load transport was estimated. We calculated that from 2001-2007 the average annual transport oscillated between 8 Mt yr -1 and 6 Mt yr -1 . An interesting aspect that makes the Araguaia unique when compared to other large alluvial rivers of Brazil is the relation between sandy load and wash load. The Araguaia at Aruana carries up to ~57% of the total sediment load as sandy load. We can now conclude that wash load just represents near 43 to 49% of the total sediment load in this system. Our results demonstrate that previous works overestimated the total wash load transported by the Araguaia. Taking into account that these are the first systematic results on wash load transport in the Araguaia, proposed human interventions in this system affecting sediment flows such as dams can be extremely harmful for the fluvial system. A more systematic analysis of sediment transport and an integrated and multidisciplinary plan of basin management must be done so that the detrimental effects of these human interventions will be understood. Resumen: Con un area drenaje ~377.000 km2 y un caudal medio anual ~ 6.420 m 3 s -1 el Rio Araguaia es el principal rio que drena el Brasil Central y el Bioma Cerrado. El Rio Araguaia es un sistema anabranching tipo arenoso que ha sufrido importantes cambios geomorfologicos y sedimentologicos como consecuencia las altas tasas deforestacion sufridas por su cuenca durante las ultimas decadas. Sin embargo, poco se conoce sobre el transporte sedimentos lavado (limo y arcilla) en este sistema. Aqui se presentan los primeros datos sistematicos la carga lavado del Rio Araguaia en la estacion hidrometrica Aruana. Se colectaron y analizaron en total 140 muestras obtenidas en 20 trabajos campo. Se estimo que el transporte sedimentos lavado entre 2001 y 2007 oscilo entre aproximadamente 8 Mt ano -1 y 6 Mt ano -1 . Un aspecto interesante que hace del Araguaia un sistema particular cuando comparado a otros grandes sistemas aluviales Brasil, es que la relacion entre la carga lavado y la carga arenosa o carga de fondo (bedload) es muy alta. El Araguaia transporta hasta 57% del total sedimentos como carga arenosa y la carga sedimentos lavado representa
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