Flow regime and flood dynamic of the Araguaia River, Brazil
Sâmia
Aquino, Universidade Estadual de Maringá, PR, s.aquino@hotmail.com
Edgardo
M.
Latrubesse, Universidade Federal de Goiás, GO, latrubes@terra.com.br
(Presenting)
The Araguaia is a large tropical river of South America with a drainage area of almost 400,000 km², a mean annual discharge of 6,500 m³/s, and a peak discharge of up to 26,283 m³/s. It is the main fluvial system draining the savanna environments of Central Brazil. Geomorphological studies on the Araguaia are scarce. Here we present some result on the hydrogeomorphological behavior of this large system with focus on flow regime and flood transmission. With an extension of 2,800 m the Araguaia can be divided in three reaches: upper, middle and lower. The middle reach is characterized by a well developed alluvial plain while the upper and lower reaches run on bedrock. The flood dynamic was studied by daily and mean monthly data discharge data, transverse sections, stages, and depth, velocity and width data for a historical series of three decades (1970-1999) of eight gauge stations operated by the Brazilian Geological Survey. Hydrographs, recurrence of flows, time duration of flows, diagrams of discharge variability, hydraulic geometry parameters, drainage area vs. discharge ratios and others parameters were used for modeling the flood dynamic of the system. Three types of floods were identified being named types A, B and C.
Type A characterized by a large storage of water in the alluvial plain of the middle reach. In this type of transmission, discharges are decreasing downstream along the middle reach with lost of water of the 30%, and then increase slowly and persistently along the lower reach. Type B is a normal transmission of floods with a light increase of water discharge while the drainage area increases. Type C is characterized by stable discharges along the middle reach and loss of water along an abandoned channel of the Araguaia River, the Javaes River, now occupied by a anomalous tributary which separates from the Araguaia and meets the main course again downstream.
Submetido por Thiago Morato de Carvalho em 25-MAR-2004
Tema Científico do LBA: SH (Hidrologia e Química das Águas)