Hydrological modeling for settling pond management in nickel mines: the Case of Hinatuan Mining Corporation in Tagana-an, Surigao del Norte, Philippines

Sedimentation and overflow in settling ponds, exacerbated by intense rainfall, significantly increase sediment levels and degrade water quality in downstream and coastal areas, impacting ecosystems and local communities. Effective hydrological modeling, though widely used in water resource management, remains underexplored for settling pond management in nickel mining operations. Hence, this study investigated hydrological processes, particularly water yield within the nickel mining area, as a foundation for settling pond management in Tagana-an, Surigao del Norte, Philippines. Using the Soil and Water Assessment Tool Plus (SWAT+) model and in-situ measurements, the research evaluated streamflow patterns and settling pond capacity in the mining area. The analysis included datasets on land cover, soil types, rainfall, and other climatic conditions to simulate water yield and assess the impact of mining activities on water resources. Statistical metrics such as Nash-Sutcliffe Efficiency (NSE, 0.61 & 0.73), Percent Bias (PBIAS, -11.76 & -1.77), RMSE-standard deviation ratio (RSR, 0.62 & 0.52), and Coefficient of Determination (R2, 0.86 & 0.94) showed strong agreement between simulated and observed streamflow in both calibration and validation phases. The study highlighted the critical importance of responsible mining practices, stressing the need to increase settling pond capacity, perform regular pond desilting to manage discharges during high rainfall events, implement emergency overflow structures, establish real-time monitoring systems, and adopt sustainable land management practices through progressive mine reforestation to restore ecosystem stability in the nickel-mined area.