Coupling Hydrological and Water Quality Models for Assessing Coal Mining Impacts on Surface Water Resources

Considering global changes and local trends and stresses, increasing water demand, and the uncontrolled release of nutrients and chemicals to freshwaters, this work focuses on (i) determining the main pollutants found in a specific coal-mining region of Colombia, (ii) modelling their fate and transport in water and (iii) estimating their corresponding polluting loads. The region chosen as the case study is the Lenguazaque River Catchment, where coal mining, agriculture and an ecosystem of Paramo overlap, and discharges of untreated domestic wastewater to the receiving waters are also occurring. Comprehensive hydrological and water quality data were collected, a hydrological model of the catchment (SWAT) and a river water quality model (WASP 8) were implemented, calibrated and coupled. As a result, we obtained a model that allows simulating actual and prospective pollution scenarios, and estimating the loads of conventional pollutants and toxic substances. Regarding conventional pollutants, excessive nutrients, pathogens, solids and oxygen demanding substances, along with a pH tending to acidity were found. Regarding toxic substances, the amounts of Fe, Mg, Mn, Cl^-, S, and their species were determined. Based on these results, an analysis of the most likely pollution sources for coal mining, agriculture and untreated domestic wastewater is presented. Also conclusions on the necessity of approaching integrally impacts assessments, and suggestions for addressing uncertainty and pollution disaggregation in future research projects are made.