This study was carried out to estimate heavy metal loads at plain area of the rural watersheds during farming season in 2006. The experimental area was belonging to Geum River watershed. That was located at the center of South Korea. Water samples were corrected at two kinds of aspects. One is regular sampling(every two month) and the other is irregular sampling(every rainfall event). The result showed that heavy metal properties of regular samples were highest at May and June with lively agricultural activities. Heavy metal concentration of irregular samples was lower than that of regular samples. But the heavy metal loads of irregular samples were high. The correlation between each heavy metals of regular samples was following as Mn-Cd > Mn-Fe > Mn-Al > Fe-Al > Al-Cd. The correlation of irregular samples was following as Fe-AI > Zn-Mn > Fe-Cd > Cd-Al. Loading rates of daily discharge the plain area of designed rural watershed during farming season were Al 3.070 kg/day, Cu 0.526 kg/day, Fe 0.745 kg/day, Zn 0.314 kg/day, Cd 0.010 kg/day, Cr 0.055 kg/day, Mn 0.140 kg/day and Pb 0.098 kg/day. Loading rate of discharge with heavy metals during the survey period was Al(577.23 kg) > Fe(140.08 kg) > Cu(98.93 kg) > Zn(58.99 kg) > Mn(26.34 kg) > Pb(18.51 kg) > Cr(10.34 kg) > Cd(1.93 kg).