Abstract Ground-penetrating radar (GPR) is a convenient tool for volumetric soil water content (VSWC) estimation in hydrological and agricultural studies. Although case studies have been widely carried out, little attention has been paid to subsoil moisture estimates. In this research, we investigated three-dimensional soil moisture variation down to a depth of 1 m and the effect of rainfall events on spatial soil moisture dynamics. GPR surveying lines were conducted both before and after a heavy rainfall event to map the VSWC. Soil sampling and time domain reflectometry (TDR) probe data at different depths (20, 40, 60, 80, and 100 cm) were acquired. Our results demonstrated that there was a significant correlation between the dielectric constants and VSWCs at all depths. The established relationships for the different depth ranges had a low VSWC discrepancy when the dielectric constants ranged from 10 to 15. The effective range of each variogram was larger than 20 m, except for that of the 0–100 cm VSWC map after rainfall. In addition, the validation diagrams using corrected TDR values demonstrated relatively reliable VSWC maps. Approximately 89% of the variation in VSWC could be explained by the dielectric constants in the depth range of 0–40 cm, and VSWC predictions at this soil depth outperformed those at other depth ranges, with an overall RMSE of 0.027 m3 m−3 and R2 of 0.725. Furthermore, we also monitored the effect of precipitation on the accuracy of the VSWC prediction on shallow surfaces. Our study shows that three-dimensional soil moisture dynamics can be accurately estimated at the field scale by integrating GPR interpretation and spatial extrapolation methods.

中文翻译：

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使用 GPR 绘制土壤体积含水量对野外强降雨事件的响应

摘要 探地雷达 (GPR) 是水文和农业研究中估算土壤体积含水量 (VSWC) 的便捷工具。尽管案例研究已被广泛开展，但对底土水分估算的关注很少。在这项研究中，我们调查了深度为 1 m 的三维土壤水分变化以及降雨事件对空间土壤水分动态的影响。在强降雨事件之前和之后都进行了 GPR 测量线以绘制 VSWC。获取了不同深度（20、40、60、80 和 100 厘米）的土壤采样和时域反射计 (TDR) 探测数据。我们的结果表明，介电常数与所有深度的 VSWC 之间存在显着相关性。当介电常数在 10 到 15 之间时，不同深度范围的既定关系具有较低的 VSWC 差异。每个变异函数的有效范围大于 20 m，除了降雨后 0-100 cm VSWC 地图的有效范围。此外，使用校正 TDR 值的验证图展示了相对可靠的 VSWC 地图。VSWC 中大约 89% 的变化可以用 0-40 cm 深度范围内的介电常数来解释，并且该土壤深度的 VSWC 预测优于其他深度范围内的预测，总体 RMSE 为 0.027 m3 m-3 和R2 为 0.725。此外，我们还监测了降水对浅表 VSWC 预测精度的影响。