This study investigates how groundwater table (GWT) fluctuations control real-time slope deformation in an open-pit coal mine and quantifies their effect on slope safety factor (SF). The research purpose is to establish the statistical link between GWT rise and deformation velocity measured by Slope Stability Radar (SSR), estimate landslide time using the inverse-velocity method, and evaluate SF sensitivity to GWT using the Bishop Simplified Method to inform an adaptive Triggered Action Response Plan (TARP). Field monitoring with SSR was carried out over 5 days (30 Sep–4 Oct 2024) on the southern slope of Pit Banko (Tanjung Enim, South Sumatra), complemented by laboratory shear tests and stability simulations. We find a strong correlation between GWT rise (~70→90 m asl) and velocity acceleration (2.88→22.51 mm/h), culminating in a medium-scale failure. The best failure-time prediction (VCP-60) differed by only 44 minutes from the actual event. Each 5 m increase in GWT reduced SF by 18.7%, underscoring groundwater control as a critical mitigation lever. The SSR+GWT-based TARP reduced false alarms and sharpened response triggers, aligned with Indonesian regulations and international guidance. The novelty of this study is integration of real-time SSR deformation with groundwater-sensitive SF to drive threshold-based TARP decisions in a tropical open-pit context.