Soil Water Infiltration Measurements Using Electrical Impedance Tomography

1J. A. Gutiérrez Gnecchi, 1E. Marroquín Pineda, 2A. Gómez-Tagle Chávez, 2A. Gómez-Tagle Rojas,

1J. Correa Gómez, 1J.C. Herrera García.

1Instituto Tecnológico de Morelia, Departamento de Ingeniería Electrónica, Avenida Tecnológico 1500, Col. Lomas de Santiaguito. C.P. 58120, Morelia, Michoacán, México,

Email: agnecchi@itmorelia.edu.mx

2INIRENA, Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Michoacán, México

ABSTRACT

Characterizing hydraulic properties of different types of soils is of great importance for agricultural and geological studies. In-situ measurement of hydraulic variables such as soil hydraulic conductivity is a time-consuming task since data has to be recorded at fixed time intervals over a period of minutes or hours depending on the type of soil. Moreover, it is still necessary to use real data for validating models. For instance, hysteresis in the soil water retention function is a particularly difficult parameter to estimate.

This paper presents the design of an automated soil infiltration single-ring measurement device. A data logger is used for measuring the liquid level change of the 85 cm Marriotte-type column, as the water infiltrates at a rate by maintaining a small negative pressure on the water as it moves out of the infiltrometer. A phantom fitted with 16 plate-type electrodes is embedded in the measurement site underneath the water outlet. The recorded data is used for determining soil saturated hydraulic conductivity whereas the EIT system produces images of the water movement through the material below the land surface whose water saturation fluctuates. Thus, a set of images can be used for measuring drainage properties as well. This has important implications for improving computer modelling and soil characterization.

Keywords Soil properties, Electrical Impedance Tomography, hydraulic conductivity, Infiltrometer, multimodal EIT.