[en] A latest thermokarst lake sampling program was carried out in the Source Area of the Yellow River in September, 2019. Isotopic signatures in water including δ¹⁸O, δ²H and ²²²Rn activities in thermokarst lakes and groundwater were systematically reported. Furthermore, lake water balance metrics and groundwater contributions to lakes were quantified via two isotope mass balance models. Results showed the robust but complex hydrological responses driven by progressive permafrost thaw. Further quantifying the relations between water volumes and other observed biogeochemical impacts to understand the mechanisms in geochemical feedbacks driven by permafrost degradation was needed. (author)