电阻率成像法在董志塬固沟保塬水分场监测中的应用

近年来,电阻率成像法(Electrical Resistivity Tomography,ERT)在土壤水分场监测方面受到广泛关注。为解决ERT测量结果难以直接表达土壤含水量的问题,以董志塬固沟保塬工程相关的五个试验点为研究对象,对每个试验点进行了ERT测量和土壤水分实时点位观测,建立了ERT测量的土壤电阻率与电容式水分传感器测量的土壤体积含水量之间的单变量函数模型。结果表明:幂函数模型能够较好地描述土壤电阻率与体积含水量之间的相关关系。此外,研究发现土壤含水量的实测值与估算值之间表现出极显著的线性相关关系,指示估算的土壤含水量有较高的准确性;同时发现当土壤含水量低于22%时,估算的含水量大于实测含水量;高于22%时,估算的含水量小于实测含水量。利用ERT测量的土壤电阻率,进行幂函数转换后形成二维土壤含水量信息,在董志塬固沟保塬二维土壤水分场监测中具有适用性。

Application of Electrical Resistivity Tomography (ERT) to monitor soil moisture distribution in the backfilling area of the gully head through gully consolidation and tableland protection on the Dongzhi loess tableland

Background, aim, and scope In recent years, the project of Gully Consolidation and Tableland Protection (GCTP) has been implemented to control the headward erosion in the Dongzhi loess tableland. One of the GCTP methods is refilling the area of the gully head and holding back the headward erosion. However, soil structure of the refilled area is totally different from the original tableland and the laws and paths of water migration also change a lot. How can we accurately monitor the water migration in the deep profile of the refilled area is an urgent issue, which is meaningful for controlling the soil erosion and disasters in the refilled area. In recent years, the geophysical tool of Electrical Resistivity Tomography (ERT) has showed the potential to monitor the soil migration processes, especially in the deep soil profile. Therefore, the method of ERT has been applied in this study and the aim is to solve the difficulty of using ERT measurement results to directly express volumetric soil moisture. Materials and methods In November 2018, five test sites that located in the Dongzhi loess tableland were selected. In each sit, the ERT measurement and the real-time point observation of soil moisture were performed. Results A univariate function model between soil resistivity measured by ERT and volumetric soil moisture measured by real-time soil moisture sensors was established. The 2-D spatial distribution of soil resistivity and volumetric soil moisture at different test sites were obtained. Discussion we found that when the soil moisture content was less than 22%, the estimated soil moisture was greater than the measured. Value of the soil moisture content was above 22%, the estimated soil moisture was lower than the measured value. The accuracy of soil moisture estimation needs to be further improved. There were many factors affecting the estimation of soil moisture, including the complexity of the surface system, the disturbance of the human engineering activities and the strong regionality of the function model. Conclusions The results showed that the relationship between soil resistivity and volumetric soil moisture could be well described by power function model. Moreover, we found that there was a significant linear correlation between the measured and estimated soil moisture content, which indicates that the estimated soil moisture through the established power function model is acceptable. Recommendations and perspectives We conclude that the 2-D soil moisture information produced by ERT and the established power function model can used in the soil moisture monitoring of the Gully Consolidation and Tableland Protection Project in the Dongzhi loess tableland.