Formed by runoff from the Jimna, Conondale, Bellthorpe and D'Aguilar ranges,[3] the river rises west of Landsborough in the hinterland surrounding the Sunshine Coast and flows generally southwest, joined by eighteen minor tributaries before being impounded by the Somerset Dam built 7 kilometres (4.3 mi) upstream from its confluence with the Brisbane River.

The Stanley River tributaries include Ewen, Crohamhurst, London, Running, Blackrock, One Mile, Monkeybong, Delaney’s, Neurem, Stony, Marysmokes, Scrubby, Sandy, Kilcoy, Sheepstation, Oaky, Byron and Reedy Creeks.

[5] Riparian vegetation around the Lake Somerset area have been almost completely cleared for grazing.

In the upper reaches bushland remains mostly intact although wildlife corridors have been fragmented and fish stocks reduced.

The Endangered Giant Barred Frog Mixophyes iteratu has also been recorded on the Stanley River.