# Real-Time Monitoring and Simultaneous Verification of Water Percolation Using Electrical Resistivity Tomography and Photography Techniques

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## Abstract

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## 1. Introduction

## 2. Method and Experiment

#### 2.1. Method

#### 2.2. Experiment

#### 2.2.1. Materials

#### 2.2.2. Design of Experiment

## 3. Data Processing

#### 3.1. Effect of Glass Trough on Electrical Resistivity and Correction Equation

#### 3.2. Numerical Simulation

#### 3.3. Comparison and Analysis between Correction Laboratory Experimental Results and Numerical Simulation Results

## 4. Results

#### 4.1. Analysis of Electrical Resistivity Profiles and Photos

#### 4.2. Analysis of the Correction of Electrical Resistivity Profiles and Photographs

## 5. Discussion

## 6. Conclusions

- (1)
- The correction equation is suitable for mitigating the impact of the glass trough on the electrical resistivity value. The corrected electrical resistivity values exhibit a stronger alignment with reality, allowing for a more realistic representation of the sand soil’s electrical resistivity value.
- (2)
- An electrical resistivity contour line value can be used to delineate the water percolation area in the electrical resistivity profile and correct the electrical profile. The areas of relatively low electrical resistivity, delineated by the 2000 Ω·m or the 8000 Ω·m contour lines in the electrical resistivity profiles and the 160 Ω·m or the 120 Ω·m contour lines in the correction electrical resistivity profiles, exhibit a remarkable correspondence with the wetting area captured in the simultaneous photographs. While the values of 2000 Ω·m and 8000 Ω·m are influenced by the boundaries, the identified low-resistivity anomaly area, which changes over time, can reflect the process of water percolation.
- (3)
- The wetting pattern of point source water percolation in the sand was determined. The wetting area captured in the photograph exhibits a bulb-shaped pattern, while the low-resistivity anomaly detected using ERT has a half-ellipse shape.
- (4)
- The combined use of ERT and photography techniques allowed us to visualize and verify the water percolation process simultaneously. ERT enables one to visualize the water percolation process and identify both the temporal and spatial distribution of water percolation, while photography serves as a means of verification. This approach can be applied in order to physical model water percolation in agricultural irrigation, pollution studies, landslide assessments, etc.

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Sketch diagram of water supply system and ERT system; 1# and 15# are the first and the fifth electrode in the measurement line.

**Figure 3.**Models for forward modeling and electrode setup:(

**a**–

**d**) are model 1, model 2, model 3, and model 4, respectively.

**Figure 4.**Forward modeling resistivity profile: (

**a**–

**d**) are the resistivity profiles from model 1, model 2, model 3, and model 4, respectively.

**Figure 5.**Photographs showing the electrical resistivity and correction of electrical resistivity profiles. P-0 min–P-60 min, 0 min–60 min, and C-10–C-60 min are photographs showing the electrical resistivity profiles and correction electrical resistivity profiles obtained during the continuous percolation for 0–60 min, respectively; (

**a**) is the 0 min photograph and electrical resistivity; (

**b**–

**g**) are 10 min–60 min photographs and the electrical resistivity and correction electrical resistivity profiles. The grid in the photograph is 5 cm × 5 cm. A black rectangle is used to delineate the area including the wetting area.

Media Diameter (mm) | Mass Percent (%) |
---|---|

>5 | 0.4 |

2 | 7.8 |

0.5 | 51.2 |

0.45 | 32.1 |

0.074 | 7.6 |

<0.074 | 0.9 |

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**MDPI and ACS Style**

Du, L.; Dou, J.; Mizunaga, H.; Zong, Z.; Zhu, W.; Dong, X.; Wu, W.
Real-Time Monitoring and Simultaneous Verification of Water Percolation Using Electrical Resistivity Tomography and Photography Techniques. *Water* **2023**, *15*, 3999.
https://doi.org/10.3390/w15223999

**AMA Style**

Du L, Dou J, Mizunaga H, Zong Z, Zhu W, Dong X, Wu W.
Real-Time Monitoring and Simultaneous Verification of Water Percolation Using Electrical Resistivity Tomography and Photography Techniques. *Water*. 2023; 15(22):3999.
https://doi.org/10.3390/w15223999

**Chicago/Turabian Style**

Du, Liang, Jie Dou, Hideki Mizunaga, Zhongling Zong, Wenjin Zhu, Xiaotian Dong, and Wenbo Wu.
2023. "Real-Time Monitoring and Simultaneous Verification of Water Percolation Using Electrical Resistivity Tomography and Photography Techniques" *Water* 15, no. 22: 3999.
https://doi.org/10.3390/w15223999