Impacts of Large-Scale Rare Earth Mining on Surface Runoff, Groundwater, and Evapotranspiration: A Case Study Using SWAT for the Taojiang River Basin in Southern China

Abstract

The extensive rare earth open-pit mining in the Taojiang River basin in southern China have produced a large area of bare land during the last several decades. We assessed the effects of the bare land on surface runoff, groundwater, and evapotranspiration (ET) using the Soil and Water Assessment Tool (SWAT). A total of nine parameters were calibrated using data from 2001 to 2005 and were validated using data from 2006 to 2009, with the observed daily streamflow data as the baseline scenario. The R2 and the Nash–Sutcliffe efficiency index ranged between 0.75 and 0.85 through the simulation periods. Moreover, two historic and four hypothetical land-use scenarios were investigated. Based on the capacity to affect surface runoff, groundwater, and ET, the ranking of land-use types was, from highest to lowest: rare earth bare land, urban land, pasture land, and forest land. Still, due to the relatively small area involved, the rare earth mining did not significantly deteriorate the local hydrological cycle from 2005 to 2015. Protecting the forest, paying attention to urban development, and enhancing infiltration in urban areas should be the top priorities in achieving sustainable development. The presented methodology provided a reliable impact assessment of the water balance components of large-scale open-pit mining activities.