Coupling simulation of rice growth and paddy drainage under controlled irrigation and drainage with the ORYZA2000 and DRAINMOD models

Controlled irrigation and drainage technology is a crucial water management method widely implemented in paddy fields in the cold black soil region of northeast China. Understanding the response mechanisms of rice growth and drainage under controlled irrigation and drainage is essential for achieving water conservation, pollution control, emission reduction, and high crop yields. This study conducted rice growth and drainage monitoring experiments and coupling simulations from 2020 to 2021. A combination of field experiments, data analysis, and coupling simulations using the ORYZA2000 (Rice growth simulation model) and DRAINMOD (Field-scale hydrological model) was employed to determine the key parameters for rice growth and drainage. The leaf area index, yield, irrigation and drainage and meteorological parameters were observed during the whole growth period of rice by field plot experiment. The coupling model was developed by linking the executable codes of ORYZA2000 and DRAINMOD using an Excel VBA-host script. Calibration and verification of the coupling model were performed using experimental data under controlled irrigation and drainage. The results indicated that the average simulated yields in 2020 and 2021 were 11,367 and9,900 kg/hm2, respectively, while the observed values were 11,158 and 9750 kg/hm2, respectively. The simulated values of leaf area index and yield were consistent with the observed values, and the R between the simulated and observed yields was 0.94 in the coupling model verification. The simulated leaf area index and yield were consistent with the observed values, with a correlation coefficient of over 0.90. The total simulated paddy field drainage in 2020 and 2021 were 60.5 and 67.0 mm, respectively, while the total observed values were 54.0 and 59.0 mm, respectively. The values of Nash-Sutcliffe efficiency for model correction and verification of paddy field drainage were 0.97 and 0.84, respectively. Overall, the coupling model can simulate rice growth and drainage under controlled irrigation and drainage, which addressed the limitations of a single model and enhanced simulation accuracy and reliability.