Unsaturated Soil Hydraulic Properties according to Double-Ring Infiltration of Saline Water
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OIL PHYSICS
Unsaturated Soil Hydraulic Properties according to Double-Ring Infiltration of Saline Water M. Aminia, H. Ebrahimiana, *, A. Liaghata, and H. Fujimakib aDepartment
of Irrigation and Reclamation Engineering, University of Tehran, Karaj, 31587-77871 Iran bArid Land Research Center, Tottori University, Tottori, 680–0001 Japan *e-mail: [email protected] Received January 16, 2020; revised April 13, 2020; accepted April 24, 2020
Abstract—Inverse modeling is a relatively complex procedure that allows quick estimation of soil hydraulic properties, yielding parameters for both soil water retention and unsaturated hydraulic conductivity function from a single experiment. The purpose of this research was to evaluate saline water effect on unsaturated hydraulic properties of clay loamy nonsaline-sodic soil layers and estimate these properties inversely from infiltration data using a double-ring infiltrometer.Three levels of water salinity (EC) 1.1, 2.2 and 5.8 dS/m were used for each treatment (T1, T2, and T3, respectively). Soil samples at three depths (0–20, 20–40 and 40–60 cm) were taken to measure Mualem–van Genuchten (MVG) hydraulic parameters (θr, residual water content, θs, saturated water content, α and n, shape parameters, and Ks, lab saturated hydraulic conductivity). Soil hydraulic parameters were estimated with an inverse solution using HYDRUS-1D model and infiltration data. Besides, the most sensitive MVG parameters to infiltration data (n, θs, and Ks) were inversely estimated due to difficulty in estimating several parameters simultaneously. Results showed that salinity had no significant effect on soil water infiltration and soil hydraulic conductivity changes in the specified salinity range according to the variance analyses (ANOVA).The Nash–Sutcliffe coefficient of efficiency (Ce) between simulated (HYDRUS) and measured values of cumulative infiltration data was about 0.998, indicating an excellent match. Soil water retention, as well as unsaturated soil hydraulic conductivity, were optimized with reasonable accuracy when the soil profile was assumed to be homogenous. In addition, simulated soil-water contents were quite similar to the measured values in which the values of Nash–Sutcliffe efficiency (Ce) for T1, T2, and T3 were 0.83, 0.85, and 0.85, respectively. In conclusion, the soil hydraulic parameters can be inversely estimated using the measured infiltration data through the double ring method if the soil is homogeneous. Keywords: dryland, unsaturated hydraulic conductivity, inverse solution, cumulative infiltration, HYDRUS-1D DOI: 10.1134/S1064229320110022
INTRODUCTION Water flow through unsaturated zone is very important in agricultural engineering, soil science, groundwater hydrology, and environmental engineering. Knowledge of the hydraulic properties of unsaturated soils (i.e. the retention curve, θ(h), and the hydraulic conductivity functions, K(h)) is essential for most or all studies involving water flow and solute transport in the vadose zone [23]. Mathematical models are increa
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