Sirith

The Sirith was a river in Gondor that rose in the White Mountains in eastern Lebennin, and flowed southward. South of the last outliers of the mountains it was joined by a tributary, the River Celos. At the point where it met the Great River Anduin, the port of Pelargir was built.
The Sirith was in the area of Upper Lebennin in the Eastern Gondor region. It flowed through the fortified valley of Tumladen before turning west to meet the Celos below the beacon "Sirthanc". The town of "Erynos" was located on the western shore across from where the two rivers met. South of the juncture, the two joined rivers flowed south from the beacon to the Anduin, forming the boundary with Lower Lebennin and the region of Central Gondor. The combined river also bisected the port city of Pelargir where it joined the Anduin. The Sirith was the domain of the honest River-maid Truetongue, one of the Five Sisters, though she and her sisters were widely considered a myth by the time of the War of the Ring.