Abstract
In this study, we compared water volume remaining on paddy fields after surface drainage, managed under various conditions using a computer simulation. The results were as follows: i) distribution of remaining water volume became almost homogeneous by improving leveling accuracy. This tendency was different from distribution of water remaining in case of open canal drainage or when an inclination was provided, ii) it is necessary to consider the direction of continuous ruggedness for open canal drainage or the inclination provided to decrease the remaining water volume, iii) in addition, appropriate leveling accuracy corresponding to the size of the paddy field was preferred.
