Estudo da propagação de ondas de cheia ao longo dos rios do Pantanal Mato-Grossense

Abstract

The Pantanal Mato-Grossense is one of the largest floodplains in the world and is part of the Upper Paraguay River Basin. The dynamics of flood propagation in rivers with large floodplains is complex owing to the strong river-channel interaction, allowing lateral discharges exchanges besides the exchanges of water through vertical hydrological processes such as evapotranspiration and infiltration. Knowing the hydrological processes of basins with this type of complexity is a challenge for water resources management. For predicting river basin hydrological behavior, mathematical models that simulate the hydrological processes for rainfall events of distinct magnitude have been used. This type of modeling helps further studies concerning flood prevention, flood warning systems, and provides subsidies for better managing the water resources related with fishing, leisure activities, navigation etc. In this context, this work aims to estimate flood wave travel times for the major rivers of the Pantanal Mato-Grossense, using a specific hydrologic model named SIRIPLAN, developed for rivers with floodplains with one- and two-dimensional modules, besides the vertical water processes module. Three floods with distinct magnitudes (maximum, average and minimum) were defined and simulated for each river entering the Pantanal, based on observed discharge data, and also a fourth hypothetical flood following a bell-shape but according with the maximum observed flood of the river. Thus, different tributary flows were simulated, in which they were defined as scenarios. The results showed a great influence of the floodplain in flow dampening and in the flood travel times, and such effects were quantified for each flood type and along each simulated river reach. It was shown a prevailing behavior of enlarging the magnitude of the flood leads to increasing flood travel time, as a function of the dampening effect due to river main channel overflow. Accordingly, the main channel-floodplain interaction in Pantanal is very strong, with the loss and gains of water from channel to floodplains influences the travel time. The flood magnitude was more important to travel time that exactly the hydrograph shape, as the monotone hypothetical flood presented very similar behavior to the real maximum flood, which shows several secondary peaks of discharge.