Abstract：
The B1 tailings dam of Córrego do Feijão iron-ore mine owned by Vale, S.A. company collapsed in 25 January 2019 releasing to the Ferro-Carvão stream watershed (32.6 km2) as much as 11.7 Mm3 of mine waste. A major share (8.9 Mm3) has been deposited along the stream channel and margins forming a 2.7 km2 patch. The main purpose of this study was to question whether the tailings deposit impacted the local water cycle and how. Using the Soil and Water Assessment Tool (SWAT) hydrologic model, the water balance components of 36 hydrologic response units (HRU) were calculated for pre- (S1) and post- (S2) B1 dam rupture scenarios represented by appropriate soil, land use and tailings cover. The results revealed an increase of evapotranspiration from S1 to S2, related to the sudden removal of vegetation from the stream valley and replacement with a blanket of mud, which raised the exposure of Earth\'s surface to sunlight and hence soil evaporation. For 11 HRU (10.3 km2) located around the tailings deposit, a decrease in lateral flow was observed, accompanied by an increase in percolation and a slight increase in groundwater flow. In this case, the water balance changes observed between S1 and S2 reflected a barrier effect imposed to the lateral flows by the tailings, which shifted the flows towards the vertical direction (percolation). Thus, the water followed an easier vertical route until reaching the shallow aquifer and being converted into groundwater flow. As per the modelling outcomes, the hydrologic impacts of B1 dam rupture are relevant because they affected 1/3 of Ferro-Carvão stream watershed, and hence claim for the complete removal of the tailings.
摘要：
淡水河谷拥有的CórregodoFeijão铁矿的B1尾矿坝，S.A.公司于2019年1月25日倒塌，向Ferro-Carvão流域（32.6km2）释放了多达11.7Mm3的矿山废物。主要份额（8.9Mm3）已沿着河道和边缘沉积，形成2.7km2的斑块。这项研究的主要目的是质疑尾矿沉积是否影响当地的水循环以及如何。使用土壤和水评估工具(SWAT)水文模型，计算了36个水文响应单元（HRU）的水平衡分量，以适当的土壤表示的前（S1）和后（S2）B1大坝破裂情景，土地利用和尾矿覆盖。结果表明，蒸散量从S1增加到S2，这与突然从溪谷中清除植被并用一层泥浆代替有关。这增加了地球表面暴露在阳光下，因此土壤蒸发。对于位于尾矿库周围的11HRU(10.3km2)，观察到横向流动的减少，伴随着渗滤的增加和地下水流量的轻微增加。在这种情况下,在S1和S2之间观察到的水平衡变化反映了尾矿对侧流施加的屏障效应，使流动向垂直方向移动(渗滤)。因此，水遵循更容易的垂直路线，直到到达浅层含水层并转化为地下水流。根据建模结果，B1大坝破裂的水文影响是相关的，因为它们影响了Ferro-Carvão河流域的1/3，因此要求完全清除尾矿。
