The Sirith (S. "Flowing [River]") was one of the five principal streams of Lebennin, joining the Anduin at the site of Pelargir. The river was fed by the Celos as it flowed out of the White Mountains, and was deep enough to be navigated by small boats as far as its confluence with that stream, making it the central waterway for Lebennin. Because of its depth, there were no fords across the Sirith; nor had any bridges been built over it, since it intersected no major road. Instead, most of the rural settlements along its banks provided ferry services for travelers.