With a mean annual average flow of about 200 million cubic metres per year the Murchison has a great variation in flow (1975 flow was 820 million cubic metres).  This annual flow compares with a figure of 320 million cubic metres for the Avon River (measured at Walyunga National Park), 660 million cubic metres for the Blackwood (the biggest river in W.A.’s south west), and 12,500 million cubic metres for the Ord River (greatest flow of any river in Australia - the peak flow of the Ord is enough to fill Mundaring Weir from empty to full in 38 minutes).

At 780 kilometres in length, the Murchison is Western Australia‘s second longest river (after the Gascoyne at 804 kilometres) although, depending on how the course of the Gascoyne is determined, a case could be made for the Murchison to be the longest river.

The mouth of the Murchison River was discovered on 1 April 1839 by Lieutenant George Grey during his return from an exploration of the Shark Bay area.  His boat was wrecked the previous day when an attempt was made to beach it at Gantheaume Bay.  Grey and his party walked to Perth.

Grey named the river after Sir Roderick Impey Murchison (1792-1871), a noted geologist who was elected President of the Royal Geographic Society in 1831.

The Roderick River (discovered and named by surveyor Robert Austin in 1854) and the Impey River (discovered by Austin and named by F.T. Gregory in 1858) are tributaries of the Murchison making Sir Roderick the only person who has three rivers in Western Australia named after him.

The Murchison Region is one of Western Australia’s most important pastoral areas.  Other income-generating activities are mining and tourism.