Numerical Investigation into the Effect of Irrigation Water Temperature on Soil Temperature in Paddy Fields under Saturated Irrigation

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<p>  The effects of irrigation water temperature on soil temperature in rice paddy fields under saturated irrigation are numerically clarified. A numerical model that coupled a heat transport model and a soil water movement model was employed. The governing equations of the heat transport and soil water movement were described as the heat conduction equation and the mixed form of Richards equation, respectively, and discretized by the finite element method for space and the finite difference method for time. A portion of a paddy field that is adjacent to an irrigation canal was used for the computational domain. Given the irrigation water temperatures as the Dirichlet boundary condition, the simulations of time-varying soil temperatures in the domain were implemented. In addition, the effects of the meteorological conditions on soil temperature were investigated. The results show that the irrigation water temperature has an effect on the soil temperature of a paddy field under saturated irrigation. The difference in soil temperature due to the different irrigation water temperature given as the Dirichlet boundary condition significantly appears near the ground surface; the trough or peak values are approximately equal to the difference in the irrigation water temperature, and the difference in the time-averaged soil temperature is about half of the difference in the irrigation water temperature. Consideration of the meteorological conditions makes the surface heat budget during computation period change from a negative value to a positive one, and diminishes the effect of irrigation water temperature on soil temperature. Thus, the effect of irrigation water temperature on soil temperature is small compared to that of the meteorological conditions. </p>


  • Journal of Rainwater Catchment Systems

    Journal of Rainwater Catchment Systems 20(2), 15-22, 2015

    Japan Rainwater Catchment Systems Association


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