Abstract
In this study, we determined the relationship between paddy field management and the surface drainage rate using computer simulation. The results were as follows: i) By leveling surface soil to improve the leveling accuracy, the remaining water volume reduced, but the surface drainage rate did not increase considerably. ii) When the ground surface was inclined or had temporary ditches, the remaining water volume reduced and the surface drainage rate improved. iii) The drainage outlets set at adequate intervals did not decrease the surface drainage rate considerably, even if the size of the paddy fields was increased. iv) Temporary ditches were one of the most excellent methods for increasing the surface drainage rate.
