Study region: This study was conducted at the Agula Eco-hydrological Experimental Station, located in the southeastern part of the Horqin Sandy Land, Tongliao City, Inner Mongolia, North China (43 degrees 18'48"-43 degrees 21'2"N, 122 degrees 32'30"-122 degrees 41'00"E) Study focus: This study investigates groundwater level responses to precipitation across geomorphic units (mobile dunes, fixed dunes, semi-fixed dunes, meadows) in Horqin Sandy Land from 2016 to 2023. Five time-series analysis methods (STL decomposition, wavelet analysis, cross-correlation, etc.) were applied to characterize groundwater dynamics in phreatic and weakly confined aquifers, including seasonal variability, decorrelation times, and rainfall lag effects. New hydrological insights for the region: Results demonstrate that the groundwater levels in phreatic aquifers rose by 0.64-0.97 m in dunes but remained stable/declined in meadows; weakly confined aquifers showed contrasting trends (0.33-1.08 m rise). Seasonal fluctuations peaked at 1 m in meadow phreatic aquifers and 0.55 m in meadow weakly confined aquifers, with 1-2 month lags in weakly confined systems. Decorrelation times ranged 21-40 days in phreatic aquifers and 16-29 days in weakly confined aquifers, indicating strong memory effects. Rainfall response lags varied from 1 day (meadows) to 113.5 days (fixed dunes in weakly confined aquifers), governed by soil permeability and groundwater depth. These findings provide a scientific basis for groundwater management and ecosystem restoration in desertified regions.