CN) method is used. To estimate the maximum ow in the watershed, three background moisture scenarios (CNI, CNII and CNIII) and six empirical equations proposed for rural watersheds were adopted to calculate the concentration time. To evaluate the observed upstream ow, a 34-years historical series was used, measured at the São Martinho downstream uviometric station (code 84598002), located in the outlet section of the study watershed. e results showed that the maximum ows estimated by the SCS-CN method for the conditions of CNII and CNIII had greater diff erences (-198% and -287%) compared to the observed ow. e smallest diff erences were veri ed for the CNI condition for all the analyzed return periods (2, 5, 10, 15, 20, 25, 50 and 100). Also, it was observed that, the longer is the return period, smaller the diff erence among the maximum observed and estimated ows, and, the smallest was veri ed for the 50year period, indicating that this is the most appropriate for studies of extreme events in the study watershed.