The Gwathló River System
The River Gwathlo (Greyflood) defines the southern border of Eriador. It divides the regions of Enedwaith to the south and Minhiriath to the north. It flows southwestwards to the Great Sea at Lond Daer. The Gwathlo's major tributaries include: the Bruinen, Mitheithel and the Glanduin. It is said that it takes its name from the tree-shadows of the great forest that filled these regions during the Second Age.
Bruinen (c) 2002 Kent Krumvieda
The River Bruinen (Loudwater) begins in the western Misty Mountains north east of Rivendell, where it flows southwestwards and joins the Mitheithel. The major tributary of the Bruinen is the Merrill stream that runs through Rivendell and joins the Bruinen about ten miles above the Ford of Bruinen.
The River Glanduin begins in the western Misty Mountains, south of Khazad-dum. It flows westward to meet the Hoarwell above Tharbad, where it forms the marshland known as Nin-in-Eilph or Swanfleet. The Glanduin has as its tributary the Sirannon Stream.
The River Mitheithel (Hoarwell) begins in the northwestern Misty Mountains, about hundred miles north of Rivendell. The Mitheithel flows southwest through the lands of the ancient kingdom of Rhudaur, round the woodland region of the Trollshaws. It eventually passes beneath the Last Bridge on the East-West Road, it continues south, until it meats the Glanduin above Tharbad to form the River Gwathlo.
Nin-in-Eilph (Swanfleet) is a large wetland on the borders of Eriador that forms where the River Glanduin flows into the Mitheithel to form the Gwathlo.
Sirannon Falls take their name from the stair carved beside them in the rock of the cliff. The falls are immediately beneath the West-gate of Khazad-dum, where the Gate-stream of the Sirannon made a waterfall some thirty feet in height before flowing out across the grasslands of Eregion.
The Sirannon Stream is the Gate-stream of Khazad-dum. It flows westward into Eregion and eventually empties into the River Glanduin. Sometime during the beginning of the Fourth Age the dam on the Sirannon was destroyed and the Fell Lake was drained. The monster who dwelt therein was killed and men and dwarves feasted on it's remains. Nothing remains of the still lake but a small pool of less than an acre. The pool is said to be haunted and few brave it's shores to fish.