SURFACE RUNOFF IN TWO REHABILITATION PERIODS OF A BAUXITE MINE

ABSTRACT The objective of this study was to monitor and compare runoff at 2.5 and 3.5 years of rehabilitation of a mined bauxite area with clonal planting of Eucalyptus. Seven plots were allocated for collecting runoff and precipitation was recorded with a pluviograph. The physical and environmental factors which interfere with runoff were characterized in both periods and subjected to principal component analysis (PCA) to show the most explanatory factors. The average monthly runoff percentage at 2.5 years was 0.25% (± 0.26%) of precipitation and equal (p-value<0.05) to the 3.5 years (0.15 ± 0.22%) of rehabilitation. Both values were lower than the Eucalyptus plantation area without mining (0.56%) in the same region and declivity. The high vegetation cover percentage by Eucalyptus crowns and Brachiaria sp. and the high infiltration rates were the determining factors in PCA, and may explain the statistically equal runoff values between the rehabilitation periods. The combination of good edaphic conditions and the fast coverage of the plants resulted in runoff below 1% in a rehabilitated area after bauxite mining.