关键词: 土壤优先流, 探地雷达, 染色示踪, 探地雷达特征参数, 优先流发育

Abstract:

Objective: By combining ground penetrating radar (GPR) and dye-tracing techniques, this study analyzes the spatiotemporal characteristics of soil preferential flow under different rainfall intensities and reveals the regulatory mechanisms of rainfall heterogeneity on preferential flow development. Additionally, we attempt to establish relationships between GPR characteristic parameters and preferential flow indices, clarify the applicability and limitations of GPR technology in identifying preferential flow, and provide insights for non-destructive monitoring of subsurface hydrological processes. Method: Focusing on a natural secondary forest dominated by Quercus mongolica, Acer pictum, and Populus davidiana in the Laotudingzi National Nature Reserve, Liaoning Province, dye-tracing experiments were conducted under heavy rain (35 mm) and torrential rain (60 mm) conditions. Stained profiles were excavated to visually analyze preferential flow characteristics, and preferential flow indices were used to comprehensively evaluate flow development. By analyzing four GPR waveform parameters: maximum amplitude (A_max), maximum amplitude area (S_max), total amplitude area (ΣS), and maximum time interval (T_max), combined with the dye coverage ratio (DC) of soil profiles, the vertical variation of preferential flow was explored. Three-dimensional maps of A_max changes before and after dye tracing were constructed to investigate variations in GPR parameters over time (pre-dye, 30 min, 1 h, and 24 h post-dye) and water transport processes. Result: 1) Preferential flow in the study area predominantly exhibited funnel and finger flow patterns with lateral flow characteristics. Heterogeneity exists in the water infiltration process,and DC exhibits a nonlinear decline as a whole with the deepening of the soil layer. As infiltration increased, the preferential flow index decreased (0.47→0.42), spatial heterogeneity declined (coefficient of variation: 0.66→0.28), and distribution expanded (DC: 48.78%→74.36%). 2) GPR parameters significantly correlated with DC. Post-dye A_max, S_max, and ΣS showed highly significant positive correlations (P≤0.01), while post-dye T_max showed a significant negative correlation (P≤0.05), confirming GPR’s effectiveness in quantifying preferential flow. 3) Post-dye A_max peaked at 10 cm depth, indicating intense water dynamics and highest preferential flow activity, with amplitude decreasing and flow weakening at greater depths. 4) The increase in infiltration water volume accelerated the maximum value of A_max from 1 hour to 30 minutes after staining during the observation period, indicating that the augmentation of infiltration water volume could accelerate water infiltration and expedite the development of preferential flow. Conclusion: This study elucidates the characteristics and dynamics of soil preferential flow in Laotudingzi National Nature Reserve under varying rainfall conditions. These findings indicate that an increase in infiltrated water volume accelerates the development of soil preferential flow, enabling it to reach its peak intensity within a shorter timeframe, yet paradoxically suppresses the overall extent or magnitude of preferential flow development. GPR technology effectively identifies preferential flow and correlates with its intensity, offering quantitative support for dye-tracing results, thereby aiding non-destructive monitoring of hydrological processes.

Key words: soil preferential flow, ground penetrating radar (GPR), dye tracing, GPR characteristic parameters, preferential flow development