Abstract: 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.
Keywords: Chinese Loess Plateau; ERT; soil moisture content; soil resistivity; function model