This study investigated groundwater-driven nutrient fluxes in a Yangtze Basin oxbow lake using a year of high-frequency monitoring. Water level and ²²²Rn tracing revealed a seasonal groundwater discharge pattern. This dynamic was regulated by net precipitation, which controlled lake level fluctuations and subsequent groundwater discharge rates. Associated N and P loads varied synchronously with discharge. The N/P closely matched that of lake water and correlated with chlorophyll-a dynamics.