The Namoi River descends 578 metres (1,896 ft) over its 708 kilometres (440 mi) course; passing near the towns of Gunnedah, Boggabri, Narrabri, Wee Waa and Walgett.

It rises east of Niangala and flows generally north west after its confluence with its major tributary, the Cobrabald River, then passes through the villages of Woolbrook and Bendemeer.

From here it flows north-westwards past Boggabri, Narrabri, Wee Waa and Burren Junction and eventually joins the Barwon River, near the town of Walgett.

The floodplains of the lower Namoi around Wee Waa are an important area for growing cotton which is irrigated using water from the dam.

[citation needed] Murray cod in the Namoi grow to a very large size, with fish of forty kilograms or larger being not uncommon.