Water qualities and discharge were monitored regularly in the agricultural basin during two irrigation periods and one non-irrigation period. The rate of paddy field in the basin changed within two irrigation periods, I.e. 36% (1988) and 45% (1989) due to conversion to upland field. The loadings were calculated onlyin the dry-weather days，bocause there was a little problem in measuing the discharge.
At the lowest end of the basin, the average concentrations of T-N, T-P and T-COD during the irrigation periods were 2.13mg/1 (1988) 1.68mg/1 (1989), 0.171mg/1 (1988) 0.399mg/1 (1989), and 2.5mg/1 (1988) 4.5mg/1 (1989) respectively. The tendency was found that the pollution loading outflows were higher than the inflow by irrgation. Furthermore ［0utflow loading］-［Inflow loading］during the irrigation period in 1989 were higher than 1988. This may be caused by the large amounts of loading from the paddy fields in the basin．