A study on the evolutionary characteristics and correlations between multi-scale precipitation and soil moisture at different depths in ecological sub-basins of the Loess Plateau

ABSTRACT The Wangdonggou ecological small watershed was taken as the research object. Based on the hourly monitoring data from 2020 to 2025, the multi-time-scale analysis framework of ‘hour-day-month-aggregation period’ was constructed, and the time-lag cross-correlation was adopted. The vertical lag response law of soil moisture at different depths to rainfall was systematically quantified. The core innovations are as follows: methodologically, the study achieved precise identification of the time lag between rainfall and soil water; in theory, the coupling relationship between ‘rainfall intensity, infiltration depth and lag response period’ has been quantitatively elucidated; in practice, a vegetation management plan has been proposed that prioritises herbs and shrubs, whilst requiring careful selection of tree species. The results indicate that the lag response period for the shallow layer (0–28 cm), middle layer (28–100 cm) and deep layer (100–255 cm) are 3–4 h, 23–24 h and 6–7 days, respectively; as rainfall intensity increases from light to heavy rain, the lag response period in the deep layer shortens from 9 to 3 days. This study provides a scientific basis for research into the ‘rainfall intensity-infiltration-root system’ coupling mechanisms on the Loess Plateau and for the construction of sustainable ecosystems.