Water in the wake of coal: modelling runoff in mining landscapes

Water in the wake of coal: Modelling surface runoff in open-cast mining landscapes

Open-cast coal mining fundamentally transforms landscapes — stripping vegetation, compacting soils, and altering drainage patterns in ways that generate complex and often unpredictable runoff dynamics. Understanding and predicting surface runoff in these disturbed environments is crucial for water resource management, downstream flood risk assessment, and environmental remediation planning. This study, published in Environmental Science and Pollution Research, evaluates the capability of the Soil and Water Assessment Tool (SWAT) — one of the most widely used hydrological models — to simulate surface runoff in open-cast coal mining areas in India.

The SWAT model was calibrated and validated using observed streamflow data from a mining-affected catchment in the Jharia coalfield of Jharkhand, India — one of the country's most intensively mined regions. The study found that SWAT performs well in predicting seasonal runoff patterns, but faces challenges in capturing the highly localised and episodic runoff pulses generated by impervious mine surfaces and spoil dumps. Sensitivity analysis identified land use and soil hydraulic properties as the most influential parameters, highlighting the importance of accurate post-mining land-use classification in model inputs.

The findings have practical implications for mine water management plans and for the design of drainage infrastructure in active and rehabilitated mining sites. As India continues to expand coal extraction to meet energy demand, tools like SWAT — when properly calibrated for mining-affected conditions — can provide valuable guidance for regulators and mine operators seeking to minimise hydrological impacts on surrounding water bodies and communities.

Hydrology does not respect the boundaries drawn around a mine lease. Surface runoff generated within mining areas travels downstream, affecting water quality and availability for communities and ecosystems far from the extraction site. Better hydrological modelling of mining landscapes is an essential step toward more responsible resource extraction.