Abstract
In this study, cyclic irrigation as reduction measure for murky water load was investigated in low-lying paddy field district around Lake Biwa. As a result, it was shown that the irrigation system could reduce effectively the murky water load during the puddling season. Comparing with conventional irrigation system, in which irrigation water is derived from the Lake Biwa by pumping, the cyclic irrigation system during the puddling season could reduce the potentially efflux load of up to 152 kg ha -1 in 2004 and 415 kg ha-1lin 2005, respectively. And then, total load returned to the paddy by the irrigation was 37 kg ha-1 and 204 kg ha-1, respectively. On the other hand, it was suggested that the weather condition and the management practices of the irrigation facilities had large influences on the reduction effect.
