In this study, the behavior of pollutant was calculated at Paldang reservior according to several scenarios of the accidental water pollution by means of the numerical models for forecasting water quality. Also managemental plans for situation of the accidental water pollution happening at Paldang watershed were simulated. According to the simulating results, a plan of increase of discharge at Cheongpyeong dam reduced the peak concentration of pollutants, whereas extended the time for stopping water intake. Another plan, drop of water elevation at Paldang dam, decreased seriously the time for stopping water intake although there were a little effect to decrease the peak concentration. Thus it was concluded that appropriate combinations of the plans for the increase discharge and the dropping water elevation should be used to deal with the accidental water pollution at Paldang watershed.