A novel model of water-heat coupling for water-saving irrigated rice fields based on water and energy balance: Model formulation and verification

It is necessary to quantify the hydrothermal processes by develop a water-heat coupling model in rice fields where the transfer between water and energy is dramatically violent, under the circumstance that water-saving irrigation (WSI) was widely used in rice paddy due to the increasing water scarcity. Based on the theory of energy and water balance, considering the interaction of impedance near the ground, a simplified holistic recursive model of water-heat coupling was proposed in the soil-plant-atmosphere continuum (SPAC) system at hourly and daily scales, and the parameters were fitted based on water and energy balance components measured in WSI rice fields. The model, takes various soil moisture conditions into consideration, integrates all the terms in the surface energy balance and the water balance with conventional meteorological data as inputs. Additionally, the model accounts for the specific drying-wetting cycles condition for WSI rice field in the calculation of the canopy resistance (r(c)) and the recursive process. Variations in crop growth and meteorology were also considered. The results showed that the model performed well in simulating the water and heat fluxes, and temperature profiles during the growth of the rice. This is encouraging for modelling the response of hydrothermal process to drying-wetting cycles or irrigation regimes, which is help for improving the water use efficiency in rice field. Meanwhile, this study indicates that the systemic model is efficient and useful for a better understanding the interaction between hydrological and energy processes in the WSI rice ecosystem.