Rela es entre o regime hidrol車gico e os ecossistemas aqu芍ticos da plan赤cie aluvial do rio Araguaia = Relationship between hydrology and aquatic ecosystems in the Araguaia river floodplain

作者：Samia Aquino; Edgardo Manuel Latrubesse; Edvard Elias de Souza Filho

来源：Acta Scientiarum - Biological Sciences, 2008.

• rio Araguaia
• comportamento hidrologico
• enchente
• planicie fluvial
• Araguaia river
• hydrologic behavior
• floods
• alluvial plain

O rio Araguaia se constitui no principal sistema fluvial que percorre o Brasil central. Neste artigo, s o apresentadas algumas observa es sobre o seu comportamento hidrogeomorfol車gico e suas aplica es no estudo de ecossistemas aqu芍ticos. Os resultados foram gerados pelo processamento de dados de vaz o de uma s谷rie hist車rica de 35 anos deregistro (1970 a 2004), em nove esta es hidrol車gicas, envolvendo o alto, m谷dio e baixo curso. A distribui o de vaz es no curso m谷dio resulta at赤pica nas cheias extremas, pois o rio perde at谷 30% de sua vaz o. No total, foram definidos tr那s tipos de enchentes e doismecanismos particulares de armazenamento e transfer那ncia de fluxos, que explicam as perdas de fluxos no m谷dio curso. Tr那s s o os principais fatores condicionantes da perda de vaz o: a) a exist那ncia de uma plan赤cie aluvial bem desenvolvida, b) a exist那ncia de umcomplexo de sistema de lagos na plan赤cie aluvial, c) a vegeta o dominantemente arb車rea, que freia a onda de cheia e contribui para o armazenamento de 芍gua na plan赤cie aluvial. The Araguaia river is the most important fluvial system draining the Cerrado biome of Brazil. Results are presented here on the hydrogeomorphologic behavior of this fluvial system and its effect on the floodplain ecosystems. Discharge from nine gauge stations in the upper, middle and lower course of the Araguaia River, from 1970 to 2004, were analyzed. The hydrological regime depends strongly on thetropical wet-dry climate, with floods from January to May and low water between June and September. In the upper and lower courses, there is a high variation between maximum and minimum peaks because the underdevelopment of the floodplain, while in the mediumcourse the flow peaks are smoothed by the presence of a well-developed river floodplain. In this area, the river can lose up to 30% in water discharge, which is stored in the floodplain.Three types of flood categories were defined, and two mechanisms of flow storage and transfer were identified, explaining the discharge loss in the middle course. Three main mechanisms produce the water loss mid-course: the sponge effect of the alluvial plain, theexistence of a well-developed mosaic of lakes, and an arboreal-dominated vegetation stratum of alluvial forest.