Environmental Impact of Mining Activities on Water Availability, Quality and Sediments in the Sonora River, Mexico

Abstract The aim of this study is to characterise environmental impacts associated with mining operations in the Sonora River basin, a water-scarce region of Mexico. The focus is on evaluating water availability, water quality, and sediment composition along the river. Furthermore, the quality of groundwater for human consumption is assessed. Data collected from an extensive field campaign is employed for this purpose. For the first time, measurements of groundwater levels in conjunction with satellite data have shown a substantial decline in groundwater levels in the northern part of the Sonora River basin, near the Buenavista del Cobre mine, highlighting how mining activities are directly affecting the loss of groundwater resources. Results relative to heavy metal pollution in the river’s surface water indicated the presence of hazardous metals at health-concerning concentrations in two areas in the river basin’s central region. Both assessed indices, the contamination degree factor and the Metal Evaluation Index, demonstrated significant heavy metal pollution associated with mining operations. Moreover, the sediment analysis clearly reveals various areas and mechanisms of heavy metal contamination within the watershed. The Pollutant Load Index (PLI) and the Ecological Risk Index (ERI) indicated significant ecological danger and severe contamination near a mine and in two regions where sediment deposition occurs (as evidenced by ERI > 300 and PLI > 3). This suggests a diffusive contamination process that conveys metals from the northern section of the basin to the southern areas of the Sonora River, due to the steeper slopes of upstream rivers. Lastly, groundwater sources intended for human consumption demonstrated generally good to excellent water quality, proving to be unaffected by mining operations. Findings show that in arid regions, it is crucial to regularly revise environmental effects of water-intense mining activities to ensure sustainable water use and to lessen risks to nearby ecosystems and local communities. Graphical Abstract