The water resource on earth surface is circulated and attains different forms; of which runoff is a major component. The runoff in any area depends on the amount of precipitation, terrain, soil type and characteristic, slope, land use activity in that region and many other location specific factors. There are several methodologies adopted world wide to estimate the runoff; one important and widely used techniques is the NRCS-CN method. This method uses precipitation, soil group and land use as the major input factors. The present study is carried out in a watershed, named the Vannathangarai watershed, a part of Noyyal river basin, which is a tributary of River Cauvery, a major river draining through southern India. The study reveals that runoff is positively correlated with precipitation and is very high in areas with slope