Lacustrine groundwater discharge (LGD) is crucial for water and nutrient cycling in lakes; however, its drivers in agricultural drainage lakes under intensive irrigation remain poorly understood. This study investigated how meteorological and vegetation dynamics regulate spatio-temporal patterns of LGD and pollutant fluxes in Ulansuhai Lake (UL), a representative agricultural drainage lake in arid northwest China. Based on hydrochemical indicators, a radon mass balance model, and remote sensing, results showed that the average LGD rate on the western side (10.50 mm/d) was substantially higher than that on the eastern side (3.49 mm/d), with peak LGD observed during the dry season (5.63 mm/d), followed by the normal (3.17 mm/d) and wet seasons (2.60 mm/d). Meteorological factors and vegetation coverage dynamics were identified as the primary controls of LGD and pollutant fluxes. Specifically, intensive canal irrigation supporting large-scale intensive cropland on the western side of Ulansuhai Lake created west-focused hotspots for both LGD rates and total nitrogen fluxes by influencing groundwater flow and pollutant sources. In contrast, evaporation-induced high alkalinity and well irrigation on the eastern side suppressed LGD processes and shifted fluoride flux hotspots eastward. Sensitivity analyses revealed that lake water radon concentration, groundwater radon concentration, wind speed, and water depth were the dominant factors affecting the accuracy of the radon mass balance model. This study advances the understanding of LGD and its associated pollutant fluxes from both spatial and temporal perspectives, providing a reference case for a newly emerging type of lake.