The cows manure has been used as fertilizers in farmland because of enough nutrients. However, excess nutrients can be washed off during a storm and affected on nearby waterbodies. In this paper, the runoff characteristics from farmland were studied to determine the watershed runoff rate. As results of estimating, watershed runoff rates with short-term runoff are BOD 0.6%, CODcr 0.3 %, CODMn 0.1 %, T-N 0.8 % and T-P 1.0 % On the other hand, they with long-term runoff are BOD 3.6 %, CODcr 1.0 %, CODMn 0.9 %, T-N 4.9 %
and T-P 4.8 %. It is clean that the watershed runoff rates increase according to the rainfall runoff time.
Keywords : Cows manure, Non-Point source, Rainfall, Watershed runoff rate