In a case study of the Baota landslide in the impoundment area of the Three Gorges project, the conceptual model of groundwater systems in this large-scale landslide was established by integrating the data from hydraulics, physical–chemical characteristics, environmental isotopes, and temperatures of the groundwater in the landslide. The conceptual model of groundwater systems includes the recharge, seepage, discharge condition, and trend of groundwater which is in turn controlled by the environmental factors (e.g., rainfall, reservoir impoundment, and artificial surface water recharge). This is one of the keys to predict the slope stability and to apply countermeasures to mitigate landslides.