Complex sentence: The Impey River is a river in the Mid West of Western Australia which rises south of Mount Murchison and flows East Northeast until it merges with the Murchison River of which it is a tributary.
Split into simpler sentences: The Impey River is a river in the Mid West of Western Australia. The headwaters of the Impey rise south of Mount Murchison and flows East North East until it merges with the Murchison River of which it is a tributary.