Imaging and characterization of the preferential flow process in agricultural land by using electrical resistivity tomography and dual-porosity model

Preferential flow is an important hydrological process, but the complexity of preferential flow channels and great difficulty in determining model parameters present certain challenges for its description on the field. The existing methods for parameters acquirement are mainly focus on calibrating by using observed data which show great uncertainty and non-uniqueness in results determination. The innovation of the study is that a new method of parameters acquisition is proposed by employing electrical resistivity tomography (ERT) method to solve the above problems. In our study, the process of deionized water infiltration was monitored, and characteristic parameters of preferential flow were abstract by using ERT in an agricultural land lies in Changhua Stream Basin, Zhejiang Province. To identify areas with preferential flow and matrix areas, soil resistivity, moisture as well as suction data were measured by resistivity meters and soil moisture and suction probes buried on site and thereby obtained area-specific soil water parameters for dual-porosity model. Then the infiltration process was simulated with a dual- porosity model based on the obtained parameters and then is verified by using infiltration results on site. We found that, instead of application of data fitting method, ERT might be useful for identification of preferential flow zone and matrix zone as well as providing precise parameters for preferential flow simulation. Compared with the laboratory test data, the Van Genuchten (VG) model parameters theta s, theta r, alpha, n differ by 9.4%, 19.8%,18.6% and 27.3% respectively. With an average Nash efficiency coefficient of 0.92 for 4 experimental sites, the simulation results for the dual-porosity model agreed with the field infiltration results. Hence, ERT can provide effective parameter support for water transportation under complex and challenging vadose zones, which is of great significance for the description of hydrological processes at a regional scale.

Automated summary

Preferential flow is an important hydrological process, and this study proposes a new method using electrical resistivity tomography (ERT) to acquire parameters, which has proven effective in providing precise parameters for preferential flow simulation.