An important water source of South-to-North Water Diversion Project, Danjiangkou Reservoir is less frequently impounded to full capacity at the end of flood season because of the increasing water use in Hanjiang River Basin. Based on the regularity in the occurrence time of the last flood each year in Danjiangkou Reservoir, a scheme of reservoir impoundment in late September instead of early October is proposed. Flood control safety analysis suggests that the new scheme could maintain the original flood control standard without increasing any flood risk. Moreover, the new scheme is proved to be more economically beneficial than the original one through comparisons on the basis of the actual inflow data of Danjiangkou Reservoir.