A case study on estimating soil hydraulic parameters based on the soil water flow simulation using HYDRUS-1D for upland irrigation planning
2016
Nakamura, K. (Kyoto University, Kyoto (Japan). Graduate School of Agriculture) | Ogushi, S. | Ikeura, Y. | Tanaka, Y.
It is essential to properly determine soil hydraulic properties (soil water retention curve and unsaturated hydraulic conductivity) to adequately predict soil water movement in a field when the daily water consumption for upland irrigation planning is determined based on the flow simulation. The soil hydraulic parameters for three layers from the surface were inversely determined based on the observed soil water contents at several depths in a bare field as an objective function. In order to obtain appropriate soil hydraulic parameters reproducing the observed soil contents, it was necessary to give an appropriate bottom boundary condition, to use laboratory-determined water retention parameter values and saturated hydraulic conductivity as initial values for the inverse solution, to estimate at least the saturated hydraulic conductivity, but not to include the retention parameters and the saturated hydraulic conductivity in an objective function to give greater flexibility in the optimization, and to estimate parameters for the three layers at the same time. The daily water consumptions for the grape tomato cultivation condition were evaluated according to the moisture depletion method for simulated water content profiles using the estimated soil hydraulic parameters. The simulated daily consumptions were mostly approximately 2 mm /d greater than the consumption values based on the measured soil water content profiles. However, simulated and measured values agreed well within 1 mm /d differences for some periods.
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