Abstract
The authors investigated the relationship between the length of paddy field and the inlet flow rate from the viewpoint of irrigation for puddling. The paddy field irrigation during the period of puddling is the same as the border irrigation which is one of several methods of field irrigation. There were two advance equations derived by incorporating two kinds of infiltration equations into the volume balance equation, which was used in the border irrigation. The methods determining the parameters of infiltration equation based on the observation of advance distance were established. Through irrigation for puddling in the paddy fields, the advance distances were observed at equal intervals of time. By using these values observed, the infiltration parameters were estimated, and several values of advance distances were computed as time elapsed by substituting the parameters into the advance equations. The computed result showed a good agreement with the observed data.
By varying the inlet flow rate, the advance distances were computed and the relationship between the length of longer side and the inlet flow rate was investigated for water to reach the downstream end within allowed time. Result shows that the longer the longer side of the paddy field becomes, the larger the inlet flow rate is required for water to reach the downstream end within allowed time. Therefore it can be clearly shown that, if the inlet flow rate for the length of longer side of 100m is regarded as a standard, and the inlet flow rate is increased in correspondence with the ratio which extended the length of longer side is divided by 100 m, the irrigating water will reach the downstream end within allowed time.
