Title: Curve number estimation using rainfall and runoff data from five catchments in Sudan
Abstract: Abstract The United States Natural Resources Conservation Services Curve Number (NRCS-CN) method uses the CN and rainfall to calculate runoff. However, there are still some uncertainties in the method, such as choosing the most appropriate CN value. Therefore, this study attempts to evaluate the effectiveness of using the NRCS-CN method to estimate the runoff of five catchments in Sudan. For each catchment, CN values were obtained from the number of observed rainfall-runoff events using the NRCS table, arithmetic mean, median, and geometric mean methods. For each method, Nash–Sutcliffe efficiency (NSE) was obtained to evaluate the fit between the observed and runoff, and negative NSE values were found for all methods. Negative values of NSE indicate that the observed runoff and estimated runoff are not well fitted, and the NRCS-CN method is not suitable for runoff calculation in the study areas.