Processos hidrossedimentológicos em diferentes escalas espaço temporais no bioma Mata Atlântica.

Abstract

This study aims to evaluate the hydrosedimentological processes at different time-space scales in the Floresta Atlântica biome, by monitoring a volumetric lysimeter of 1m³ in size and two built-in basins: Rancho do Amaral (4,45km²) and Rincão do Soturno (11.98km²), inserted in the interfluve areas of Vacacaí Mirim basin, Santa Maria-RS. The selected variables for implementation of this study were monitored during the year 2009, the precipitation being monitored with the aid of two automatic pluviographs, the level of the river with the help of two automatic linígrafos. Liquid and solid discharge measurements were also carried out in stations installed at the mouth of each river, samples of sediments in suspension were collected with automatic punctual samplers and concentration of suspended sediment were monitored through two turbidity probes. Rancho do Amaral basin showed average annual liquid discharge of 0.078m³/s, specific flow of 17.98L/s.Km² and solid of 0.093 ton/day, while the Rincão do Soturno basin showed average annual liquid discharge of 0.164m³/s, specific flow of 13.36L/s.Km² and solid of 0.157 ton/day. Five representing events were selected to compare the concentration of suspended sediments between the two basins, leading to some conclusions: Rincão do Soturno basin presents a higher concentration of 52.58 mg/L in suspended sediments, equivalent to 67%, compared to Rancho do Amaral basin, in precipitation events. In precipitation absence, the superiority is of 7.29 mg/L, equivalent to 34%. The time scale for the sediment yield was evaluated at intervals of 10 minutes to 1 day, noting that the readings of 10 minutes showed higher production and with increasing time scale the decrease tends to stabilize. Of the material collected in the lysimeter, 58% was fine sand. In Rancho do Amaral basin, collected material was also predominantly fine sand, with 46%. In the Rincão do Soturno basin, the material was predominantly silt, with 47.55%. Comparing the sediment yield per m2 in the two monitored basins, itappears that the Rancho do Amaral basin s production is 20% higher than in the Rincão do Soturno basin.